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EE462

Electric Machines

PROJECT REPORT VARIABLE SPEED DC MOTOR DRIVE

Done By:

ID# NAME SEC# E-mail Tel# 212417 Al-Hajjaj, Muhammad 02 s212417@kfupm.edu.sa 0500099661

Done for:

Dr. M. Abido

Due date 21 May 2006

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TABLE OF CONTENTS

1.0 DC MOTOR THEORY 3 1.1 Torque 6 1.2 Generator Action in a Motor 7 1.3 DC Motor Theory Summary 8 1.4 TYPES OF DC MOTORS 8

2.0 DC DRIVE FUNDAMENTALS 17

2.1 DC MOTORS 17 2.2 TYPICAL ADJUSTMENTS 23 2.3 DC DRIVES - PRINCIPLES OF OPERATION 26 2.4 DC MOTOR CONTROL CHARACTERISTICS 27 2.5 TYPES OF VARIABLE SPEED DC DRIVES 28

3.0 RECOMMENDATIONS 42 4.0 CONCLUSIONS 44 5.0 REFERENCES 46

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1.0 DC MOTOR THEORY: Inducing a Force on a Conductor. There are two conditions which are necessary to produce a force on a conductor:

i. The conductor must be carrying current.

ii. The conductor must be within a magnetic field. When these two conditions exist, a force will be applied to the conductor, which will attempt to move the conductor in a direction perpendicular to the magnetic field. This is the basic theory by which all DC motors operate. Theory of Operation (Figure 1), Left-Hand Rule for Current-Carrying Conductors Every current-carrying conductor has a magnetic field around it. The direction of this magnetic field may be found by using the left-hand rule for current-carrying conductors. When the thumb points in the direction of current flow, the fingers will point in the direction of the magnetic field produced, as shown in Figure 1. If a current-carrying conductor is placed in a magnetic field, the combined fields will be similar to those shown in Figure 2. The direction of current flow through the conductor is indicated with an "x" or a "•". The "x" indicates the current flow is away from the reader, or into the page. The "•" indicates the current flow is towards the reader, or out of the page.

Figure 1: Left-Hand Rule for Current-Carrying Conductors

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Figure 2: Current-Carrying Conductor in a Magnetic Field

Above the conductor on the left, the field caused by the conductor is in the opposite direction of the main field, and therefore, opposes the main field. Below the conductor on the left, the field caused by the conductor is in the same direction as the main field, and therefore, aids the main field. The net result is that above the conductor the main field is weakened, or flux density is decreased; below the conductor the field is strengthened, or flux density is increased. A force is developed on the conductor that moves the conductor in the direction of the weakened field (upward). Above the conductor on the right, the field caused by the conductor is in the same direction as the main field, and therefore, aids the main field. Below the conductor on the right, the field caused by the conductor is in the opposite direction of the main field, and therefore, opposes the main field. The net result is that above the conductor the field is strengthened, or flux density is increased, and below the conductor, the field is weakened, or flux density is decreased. A force is developed on the conductor that moves the conductor in the direction of the weakened field (downward). In a DC motor, the conductor will be formed in a loop such that two parts of the conductor are in the magnetic field at the same time, as shown in Figure 3. This combines the effects of both conductors to distort the main magnetic field and produce a force on each part of the conductor. When the conductor is placed on a rotor, the force exerted on the conductors will cause the rotor to rotate clockwise, as shown on Figure 3. You can think of these magnetic lines of force as rubber bands that are always trying to shorten themselves. The lines of force above the

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conductor exert a downward force due to the magnetic lines of force trying to straighten themselves.

Figure 3: Motor Action The above explanation of how a force is developed is convenient; however, it is somewhat artificial. It is based on a fundamental principle of physics which may be stated as follows: "A current-carrying conductor in a magnetic field tends to move at right angles to that field." Another important way to show the relationship between the current-carrying conductor, magnetic field, and motion, is the right-hand rule for motors, as shown in Figure 4.

Figure 4: Right hand rule for motors

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The right-hand rule for motors shows the direction in which a current-carrying conductor moves in a magnetic field. When the forefinger is pointed in the direction of the magnetic field lines, and the center finger is pointed in the direction of current flow, the thumb will point in the direction of force (motion). 1.1 Torque Torque is defined as that force which tends to produce and maintain rotation. The function of torque in a DC motor is to provide the mechanical output or drive the piece of equipment that the DC motor is attached to. When a voltage is applied to a motor, current will flow through the field winding, establishing a magnetic field. Current will also flow through the armature winding, from the negative brush to the positive brush as shown in Figure 5. Since the armature is a current- carrying conductor in a magnetic field, the conductor has a force exerted on it, tending to move it at right angles to that field. Using the left-hand rule for current- carrying conductors, you will see that the magnetic field on one side is strengthened at the bottom, while it is weakened on the other side. Using the right-hand rule for motors, we can see that there is a force exerted on the armature which tends to turn the armature in the counter-clockwise direction. The sum of the forces, in pounds, multiplied by the radius of the armature, in feet, is equal to the torque developed by the motor in pound-feet (1b - ft). It is evident from Figure 5 that if the armature current was reversed, but the field was the same, torque would be developed in the opposite direction. Likewise, if the field polarities were reversed and the armature remained the same, torque would also be developed in the opposite direction. The force that is developed on a conductor of a motor armature is due to the combined action of the magnetic fields. The force developed is directly proportional to the strength of the main field flux and the strength of the field around the armature conductor. As we know, the field strength around each armature conductor depends on the amount of current flowing through the armature conductor.

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Figure 5: Armature Current in a Basic DC Motor T = KFIa Where T = torque, lb-ft, K = a constant depending on physical size of motor, F = field flux, number of lines of force per pole Ia = armature current 1.2 Generator Action in a Motor A generator action is developed in every (CEMF) motor. When a conductor cuts lines of force, an EMF is induced in that conductor. Current to start the armature turning will flow in the direction determined by the applied DC power source. After rotation starts, the conductor cuts lines of force. By applying the left-hand rule for generators, the EMF that is induced in the armature will produce a current in the opposite direction. The induced EMF, as a result of motor operation, is called counter electromotive force, or CEMF, as illustrated in Figure 6.

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Figure 6: Counter electromotive Force (CEMF) 1.3 DC Motor Theory Summary

There are two conditions necessary to produce a force on a conductor: - i. The conductor must be carrying current.

ii. The conductor must be within a magnetic field.

The right-hand rule for motors states that when the forefinger is pointed in the direction of the magnetic field lines, and the center finger is pointed in the direction of current flow, the thumb will point in the direction of motion.

The function of torque in a DC motor is to provide the mechanical output to drive the piece of equipment that the DC motor is attached to.

Torque is developed in a DC motor by the armature (current-carrying conductor) being present in the motor field (magnetic field).

CEMF is developed in a DC motor by the armature (conductor) rotating (relative motion) in the field of the motor (magnetic field).

The function of the voltage that is developed in a DC motor (CEMF) opposes the applied voltage and results in the lowering of armature current.

The speed of a DC motor may be changed by using resistors to vary the field current and, therefore, the field strength.

1.4 TYPES OF DC MOTORS

There are three basic types of dc motors: (1) Series motors. (2) Shunt motors, and (3) compound motors. They differ largely in the method in which their field and armature coils are connected.

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Series DC Motor

In the series motor, the field windings, consisting of a relatively few turns of heavy wire, are connected in series with the armature winding. The same current flowing through the field winding also flows through the armature winding. Any increase in current, therefore, strengthens the magnetism of both the field and the armature.

Because of the low resistance in the windings, the series motor is able to draw a large current in starting. This starting current, in passing through both the field and armature windings, produces a high starting torque, which is the series motor's principal advantage.

The speed of a series motor is dependent upon the load. Any change in load is accompanied by a substantial change in speed. A series motor will run at high speed when it has a light load and at low speed with a heavy load. If the load is removed entirely, the motor may operate at such a high speed that the armature will fly apart. If high starting torque is needed under heavy load conditions, series motors have many applications. Series motors are often used in aircraft as engine starters and for raising and lowering landing gears, cowl flaps, and wing flaps.

Shunt DC Motor

In the shunt motor the field winding is connected in parallel or in shunt with the armature winding. The resistance in the field winding is high. Since the field winding is connected directly across the power supply, the current through the field is constant. The field current does not vary with motor speed, as in the series

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motor and, therefore, the torque of the shunt motor will vary only with the current through the armature. The torque developed at starting is less than that developed by a series motor of equal size.

The speed of the shunt motor varies very little with changes in load. When all loads are removed, it assumes a speed slightly higher than the loaded speed. This motor is particularly suitable for use when constant speed is desired and when high starting torque is not needed.

Compound DC Motor

The compound motor is a combination of the series and shunt motors. There are two windings in the field: a shunt winding and a series winding. The shunt winding is composed of many turns of fine wire and is connected in parallel with the armature winding. The series winding consists of a few turns of large wire and is connected in series with the armature winding. The starting torque is higher than in the shunt motor but lower than in the series motor. Variation of speed with load is less than in a series wound motor but greater than in a shunt motor. The compound motor is used whenever the combined characteristics of the series and shunt motors are desired.

Like the compound generator, the compound motor has both series and shunt field windings. The series winding may either aid the shunt wind (cumulative compound) or oppose the shunt winding (differential compound).

The starting and load characteristics of the cumulative compound motor are somewhere between those of the series and those of the shunt motor.

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Because of the series field, the cumulative compound motor has a higher starting torque than a shunt motor. Cumulative compound motors are used in driving machines which are subject to sudden changes in load. They are also used where a high starting torque is desired, but a series motor cannot be used easily.

In the differential compound motor, an increase in load creates an increase in current and a decrease in total flux in this type of motor. These two tend to offset each other and the result is a practically constant speed. However, since an increase in load tends to decrease the field strength, the speed characteristic becomes unstable. Rarely is this type of motor used in aircraft systems.

Counter E.M.F.

The armature resistance of a small, 28 volt dc motor is extremely low, about 0.1 ohms. When the armature is connected across the 28 volt source, current through the armature will apparently be

This high valve of current flow is not only impracticable but also unreasonable, especially when the current drain, during normal operation of a motor, is found to be about 4 amperes. This is because the current through a motor armature during operation is determined by more factors than ohmic resistance.

When the armature in a motor rotates in a magnetic field, a voltage is induced in its windings. This voltage is called the back or counter e.m.f. (electromotive force) and is opposite in direction to the voltage applied to the motor from the external source.

Counter e.m.f. opposes the current which causes the armature to rotate. The current flowing through the armature, therefore, decreases as the counter e.m.f. increases. The faster the armature rotates, the greater the counter e.m.f. For this reason, a motor connected to a battery may draw a fairly high current on starting, but as the armature speed increases, the current flowing through the armature decreases. At rated speed, the counter e.m.f. may be only a few volts less than the battery voltage. Then, if the load on the motor is increased, the motor will slow down, less counter e.m.f. will be generated, and the current drawn from the external source will increase. In a shunt motor, the counter e.m.f. affects only the current in the armature, since the field is connected in parallel across the power source. As the motor slows down and the counter e.m.f. decreases, more current flows through the armature, but the magnetism in the field is unchanged. When the series motor slows down, the counter e.m.f. decreases and more current flows

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through the field and the armature, thereby strengthening their magnetic fields. Because of these characteristics, it is more difficult to stall a series motor than a shunt motor.

Types of Duty

Electric motors are called upon to operate under various conditions. Some motors are used for intermittent operation; others operate continuously. Motors built for intermittent duty can be operated for short periods only and, then, must be allowed to cool before being operated again. If such a motor is operated for long periods under full load, the motor will be overheated. Motors built for continuous duty may be operated at rated power for long periods.

Reversing Motor Direction

By reversing the direction of current flow in either the armature or the field windings, the direction of a motor's rotation may be reversed. This will reverse the magnetism of either the armature or the magnetic field in which the armature rotates. If the wires connecting the motor to an external source are interchanged, the direction of rotation will not be reversed, since changing these wires reverses the magnetism of both field and armature and leaves the torque in the same direction as before.

One method for reversing direction of rotation employs two field windings wound in opposite directions on the same pole. This type of motor is called a split field motor. The single pole, double throw switch makes it possible to direct current through either of the two windings. When the switch is placed in the lower position, current flows through the lower field winding, creating a north pole at the lower field winding and at the lower pole piece, and a south pole at the upper pole piece. When the switch is placed in the upper position, current flows through the upper field winding, the magnetism of the field is reversed, and the armature rotates in the opposite direction. Some split field motors are built with two separate field windings wound on alternate poles. The armature in such a motor, a four pole reversible motor, rotates in one direction when current flows through the windings of one set of opposite pole pieces, and in the opposite direction when current flows through the other set of windings.

Another method of direction reversal, called the switch method, employs a double pole, double throw switch which changes the direction of current flow in either the armature or the field. In the illustration of the switch method. Current direction may be reversed through the field but not through the armature. When the switch is thrown to the "up" position, current flows through the field winding to establish

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a north pole at the right side of the motor and a south pole at the left side of the motor. When the switch is thrown to the "down" position, this polarity is reversed and the armature rotates in the opposite direction.

Motor Speed

Motor speed can be controlled by varying the current in the field windings. When the amount of current flowing through the field windings is increased, the field strength increases, but the motor slows down since a greater amount of counter e.m.f. is generated in the armature windings. When the field current is decreased, the field strength decreases, and the motor speeds up because the counter e.m.f. is reduced. A motor in which speed can be controlled is called a variable speed motor. It may be either a shunt or series motor.

In the shunt motor, speed is controlled by a rheostat in series with the field windings. The speed depends on the amount of current which flows through the rheostat to the field windings. To increase the motor speed, the resistance in the rheostat is increased, which decreases the field current. As a result, there is a decrease in the strength of the magnetic field and in the counter e.m.f. This momentarily increases the armature current and the torque. The motor will then automatically speed up until the counter e.m.f. increases and causes the armature current to decrease to its former value. When this occurs, the motor will operate at a higher fixed speed than before.

To decrease the motor speed, the resistance of the rheostat is decreased. More current flows through the field windings and increases the strength of the field; then, the counter e.m.f. increases momentarily and decreases the armature current. As a result, the torque decreases and the motor slow down until the counter e.m.f. decreases to its former value; then the motor operates at a lower fixed speed than before.

The rheostat speed control is connected either in parallel or in series with the motor field, or in parallel with the armature. When the rheostat is set for maximum resistance, the motor speed is increased in the parallel armature connection by a decrease in current. When the rheostat resistance is maximum in the series connection, motor speed is reduced by a reduction in voltage across the motor. For above normal speed operation, the rheostat is in parallel with the series field. Part of the series field current is bypassed and the motor speeds up.

Energy Losses in DC Motors

Losses occur when electrical energy is converted to mechanical energy (in the motor), or mechanical energy is converted to electrical energy (in the generator).

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For the machine to be efficient, these losses must be kept to a minimum. Some losses are electrical, others are mechanical. Electrical losses are classified as copper losses and iron losses; mechanical losses occur in overcoming the friction of various parts of the machine.

Copper losses occur when electrons are forced through the copper windings of the armature and the field. These losses are proportional to the square of the current. They are sometimes called I²R losses, since they are due to the power dissipated in the form of heat in the resistance of the field and armature windings.

Iron losses are subdivided in hysteresis and eddy current losses. Hysteresis losses are caused by the armature revolving in an alternating magnetic field. It, therefore, becomes magnetized first in one direction and then in the other. The residual magnetism of the iron or steel of which the armature is made causes these losses. Since the field magnets are always magnetized in one direction (DC field), they have no hysteresis losses.

Eddy current losses occur because the iron core of the armature is a conductor revolving in a magnetic field. This sets up an e.m.f. across portions of the core, causing currents to flow within the core. These currents heat the core and, if they become excessive, may damage the windings. As far as the output is concerned, the power consumed by eddy currents is a loss. To reduce eddy currents to a minimum, a laminated core usually is used. A laminated core is made of thin sheets of iron electrically insulated from each other. The insulation between laminations reduces eddy currents, because it is "transverse" to the direction in which these currents tend to flow. However, it has no effect on the magnetic circuit. The thinner the laminations, the more effectively this method reduces eddy current losses.

Inspection and Maintenance of DC Motors

Use the following procedures to make inspection and maintenance checks:

1. Check the operation of the unit driven by the motor in accordance with the instructions covering the specific installation.

2. Check all wiring, connections, terminals, fuses, and switches for general condition and security.

3. Keep motors clean and mounting bolts tight.

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4. Check brushes for condition, length, and spring tension. Minimum brush lengths, correct spring tension, and procedures for replacing brushes are given in the applicable manufacturer's instructions.

5. Inspect commutator for cleanness, pitting, scoring, roughness, corrosion or burning. Check for high mica (if the copper wears down below the mica, the mica will insulate the brushes from the commutator). Clean dirty commutators with a cloth moistened with the recommended cleaning solvent. Polish rough or corroded commutators with fine sandpaper (000 or finer) and blow out with compressed air. Never use emery paper since it contains metallic particles which may cause shorts. Replace the motor if the commutator is burned, badly pitted, grooved, or worn to the extent that the mica insulation is flush with the commutator surface.

6. Inspect all exposed wiring for evidence of overheating. Replace the motor if the insulation on leads or windings is burned, cracked, or brittle.

7. Lubricate only if called for by the manufacturer's instructions covering the motor. Most motors used in today's airplanes require no lubrication between overhauls.

8. Adjust and lubricate the gearbox, or unit which the motor drives, in accordance with the applicable manufacturer's instructions covering the unit.

When trouble develops in a dc motor system, check first to determine the source of the trouble. Replace the motor only when the trouble is due to a defect in the motor itself. In most cases, the failure of a motor to operate is caused by a defect in the external electrical circuit, or by mechanical failure in the mechanism driven by the motor.

Check the external electrical circuit for loose or dirty connections and for improper connection of wiring. Look for open circuits, grounds, and shorts by following the applicable manufacturer's circuit testing procedure. If the fuse is not blown, failure of the motor to operate is usually due to an open circuit. A blown fuse usually indicates an accidental ground or short circuit. The chattering of the relay switch which controls the motor is usually caused by a low battery. When the battery is low, the open circuit voltage of the battery is sufficient to close the relay, but with the heavy current draw of the motor, the voltage drops below the level required to hold the relay closed. When the relay opens, the voltage in the battery increases enough to close the relay again. This cycle repeats and causes chattering, which is very harmful to the relay switch, due to the heavy current causing an arc which will burn the contacts.

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Check the unit driven by the motor for failure of the unit or drive mechanism. If the motor has failed as a result of a failure in the driven unit, the fault must be corrected before installing a new motor.

If it has been determined that the fault is in the motor itself (by checking for correct voltage at the motor terminals and for failure of the driven unit), inspect the commutator and brushes. A dirty commutator or defective or binding brushes may result in poor contact between brushes and commutator. Clean the commutator, brushes, and brush holders with a cloth moistened with the recommended cleaning solvent. If brushes are damaged or worn to the specified minimum length, install new brushes in accordance with the applicable manufacturer's instructions covering the motor. If the motor still fails to operate, replace it with a serviceable motor.

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2.0 DC DRIVE FUNDAMENTALS

UNDERSTANDING DC DRIVES DC motors have been available for nearly 100 years. In fact the first electric motors were designed and built for operation from direct current power.

AC motors are now and will of course remain the basic prime movers for the fixed speed requirements of industry. Their basic simplicity, dependability and ruggedness make AC motors the natural choice for the vast majority of industrial drive applications.

Then where do DC drives fit into the industrial drive picture of the future?

In order to supply the answer, it is necessary to examine some of the basic characteristics obtainable from DC motors and their associated solid state controls.

1. Wide speed range. 2. Good speed regulation. 3. Compact size and light weight (relative to mechanical variable speed). 4. Ease of control. 5. Low maintenance. 6. Low cost.

In order to realize how a DC drive has the capability to provide the above characteristics, the DC drive has to be analyzed as two elements that make up the package. These two elements are of course the motor and the control. (The "control" is more accurately called the "regulator").

2.1 DC MOTORS

Basic DC motors as used on nearly all packaged drives have a very simple performance characteristic the shaft turns at a speed almost directly proportional to the voltage applied to the armature. Figure 1 shows a typical voltage/speed curve for a motor operating from a 115 volt control.

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From the above curve you can see that with 9 volts applied to the armature, this motor would be operating at Point 1 and turn at approximately 175 RPM. Similarly with 45 volts applied, the motor would be operating at Point 2 on the curve or 875 RPM. With 90 volts applied, the motor would reach its full speed of 1750 RPM at point 3.

From this example a general statement can be made that DC motors have "no load" characteristics that are nearly a perfect match for the curve indicated in Figure 1.

However, when operated at a fixed applied voltage but a gradually increasing torque load, they exhibit a speed droop as indicated in Figure 2.

This speed droop is very similar to what would occur if an automobile accelerator pedal was held in a fixed position with the car running on level ground. Upon starting up an incline where more driving torque would be needed, the car would slow down to a speed related to the steepness of the hill. In a real situation, the driver would respond by depressing the accelerator pedal to compensate for the speed loss to maintain a nearly constant speed up the incline.

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In the DC drive a similar type of "compensation" is employed in the control to assist in maintaining a nearly constant speed under varying load (torque) conditions.

The measurement of this tendency to slow down is called Regulation and is calculated with the following equation:

% Regulation = No Load Speed - Full Load Speed No Load Speed X 100

In DC drives the regulation is generally expressed as a percentage of motor base speed.

If the control (regulator) did not have the capability of responding to and compensating for changing motor loads, regulation of typical motors might be as follows:

HP % MOTOR REGULATION HP % MOTOR

REGULATION 1/4 13.6 1.5 8.0 1/3 12.9 2 7.2 1/2 13.3 3 4.2 3/4 10.8 5 2.9 1 6.7 7.5 2.3

One other very important characteristic of a DC motor should be noted. Armature amperage is almost directly proportional to output torque regardless of speed. This characteristic is shown by Figure 3. Point 1 indicates that a small fixed amount of current is required to turn the motor even when there is no output torque. This is due to the friction of the bearings, electrical losses in the motor materials and load imposed by the air in the motor (wind age).

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Beyond Point 1 through Point 2 and 3, the current increases in direct proportion to the torque required by the load.

From this discussion and Figure 3 a general statement can be made that for PM and Shunt Wound motors load torque determines armature amperage.

In summary, two general statements can be made relative to DC motor performance.

1. Motor Speed is primarily determined by Applied Armature Voltage. 2. Motor Torque is controlled by Armature Current (amperes).

Understanding these two concepts of DC motors provides the key to understanding total drive performance.

REGULATORS (CONTROLS)

The control provides two basic functions:

1. It rectifies AC power converting it to DC for the DC motor. 2. It controls the DC output voltage and amperage in response to various

control and feedback signals thereby regulating the motor's performance, both in speed and torque.

RECTIFYING FUNCTION

The basic rectifying function of the control is accomplished by a combination of power semiconductors (Silicon Controlled Rectifiers and Diodes) that make up the "power bridge" assembly.

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REGULATING FUNCTION

The regulating function is provided by a relatively simple electronic circuit that monitors a number of inputs and sums these signals to produce a so called "error" signal. This error signal is processed and transformed into precisely timed pulses (bursts of electrical energy). These pulses are applied to the gates of the SCR's in the power bridge thereby regulating the power output to the DC motor.

For most purposes it is not necessary to understand the electronic details of the regulator, however, in order to appreciate the regulator function it is good to understand some of the input signals that are required to give the regulator its capabilities, these are shown diagrammatically in Figure 4.

The AC to DC power flow is a relatively simple straight through process with the power being converted from AC to DC by the action of the solid state power devices that form the power bridge assembly.

The input and feedback signals need to be studied in more detail.

SET POINT INPUT

In most packaged drives this signal is derived from a closely regulated fixed voltage source applied to a potentiometer. 10 volts is a very common reference.

The potentiometer has the capability of accepting the fixed voltage and dividing it down to any value of from, for example, 10 to zero volts, depending on where it is

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set. A 10 volt input to the regulator from the speed adjustment control (potentiometer) corresponds to maximum motor speed and zero volts correspond to zero speed. Similarly any speed between zero and maximum can be obtained by adjusting the speed control to the appropriate setting.

SPEED FEEDBACK INFORMATION

In order to "close the loop" and control motor speed accurately it is necessary to provide the control with a feedback signal related to motor speed.

The standard method of doing this in a simple control is by monitoring the armature voltage and feeding it back into the regulator for comparison with the input "set point" signal.

When armature voltage becomes high, relative to the set point, established by the speed potentiometer setting, an "error" is detected and the output voltage from the power bridge is reduced to lower the motor's speed back to the "set point". Similarly when the armature voltage drops an error of opposite polarity is sensed and the control output voltage is automatically increased in an attempt to re-establish the desired speed.

The "Armature Voltage Feedback System" which is standard in most packaged drives is generally called a "Voltage Regulated Drive".

A second and more accurate method of obtaining the motor speed feedback information is called "Tachometer Feedback". In this case the speed feedback signal is obtained from a motor mounted tachometer. The output of this tachometer is directly related to the speed of the motor. Using Tachometer Feedback generally gives a drive improved regulation characteristics. When "Tachometer Feedback" is used the drive is referred to as a "Speed Regulated Drive". Most controls are capable of being modified to accept tachometer signals for operation in the tachometer feedback mode.

In some newer high performance "digital drives" the feedback can come from a motor mounted encoder that feeds back voltage pulses at a rate related to motor speed. These (counts) are processed digitally being compared to the "set point" and error signals are produced to regulate the armature voltage and speed.

CURRENT FEEDBACK

The second source of feedback information is obtained by monitoring the motor armature current. As discussed previously, this is an accurate indication of the torque required by the load.

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The current feedback signal is used for two purposes:

1. As positive feedback to eliminate the speed droop that occurs with increased torque load on the motor. It accomplishes this by making a slight corrective increase in armature voltage as the armature current increases.

2. As negative feedback with a "threshold" type of control that limits the current to a value that will protect the power semiconductors from damage. By making this function adjustable it can be used to control the maximum torque the motor can deliver to the load.

The current limiting action of most controls is adjustable and is usually called "Current Limit" or "Torque Limit".

In summary, the Regulator accomplishes two basic functions:

1. It converts the alternating Current to Direct Current. 2. It regulates the armature voltage and current to control the speed and torque

of the DC Motor.

2.2 TYPICAL ADJUSTMENTS

In addition to the normal external adjustment such as the speed potentiometer. There are a number of common internal adjustments that are used on simple small analog type SCR Drives (Silicon Controlled Rectifier Drive). Some of these adjustments are as follows:

• Minimum Speed • Maximum Speed • Current Limit (Torque Limit). IR Compensation • Acceleration Time. Deceleration Time

The following is a description of the function that these individual adjustments serve and their typical use.

MINIMUM SPEED

In most cases when the control is initially installed the speed potentiometer can be turned down to its lowest point and the output voltage from the control will go to zero causing the motor to stop. There are many situations where this is not desirable. For example there are some machines that want to be kept running at a minimum speed and accelerated up to operating speed as necessary. There is also a possibility that an operator may use the speed potentiometer to stop the motor to work on the machine. This can be a dangerous situation since the motor has only

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been brought to a stop by zeroing the input signal voltage. A more desirable situation is when the motor is stopped by opening the circuit to the motor or power to the control using the on/off switch. By adjusting the minimum speed up to some point where the motor continues to run even with the speed potentiometer set to its lowest point, the operator must shut the control off to stop the motor. This adds a little safety into the system. The typical minimum speed adjustment is from 0 to 30% of motor base speed.

MAXIMUM SPEED

The maximum speed adjustment sets the maximum speed attainable either by raising the input signal to its maximum point or turning the potentiometer to the maximum point. For example on a typical DC motor the rated speed of the motor might 1750 RPM but the control might be capable of running it up to 1850 or 1900 RPM. In some cases it's desirable to limit the motor (and machine speed) to something less than would be available at this maximum setting. The maximum adjustment allows this to be done. By turning the internal potentiometer to a lower point the maximum output voltage from the control is limited. This limits the maximum speed available from the motor. In typical controls such as our BC140 the range of adjustment on the maximum speed is from 50 to 110% of motor base speed.

CURRENT LIMIT

One very nice feature of electronic speed controls is that the current going to the motor is constantly monitored by the control. As mentioned previously, the current drawn by the armature of the DC motor is related to the torque that is required by the load. Since this monitoring and control is available an adjustment is provided in the control that limits the output current to a maximum value.

This function can be used to set a threshold point that will cause the motor to stall rather than putting out an excessive amount of torque. This capability gives the motor/control combination the ability to prevent damage that might otherwise occur if higher values of torque were available. This is handy on machines that might become jammed or otherwise stalled. It can also be used where the control is operating a device such as the center winder where the important thing becomes torque rather than the speed. In this case the current limit is set and the speed goes up or down to hold the tension 0 the material being wound. The current limit is normally factory set at 150% of the motor's rated current. This allows the motor to produce enough torque to start and accelerate the load and yet will not let the current (and torque) exceed 150% of its rated value when running. The range of adjustment is typically from 0 to 200% of the motor rated current.

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IR COMPENSATION

IR compensation is a method used to adjust for the droop in a motor's speed due to armature resistance. As mentioned previously, IR compensation is positive feedback that causes the control output voltage to rise slightly with increasing output current. This will help stabilize the motor's speed from a no load to full load condition. If the motor happens to be driving a load where the torque is constant or nearly so, then this adjustment is usually unnecessary. However, if the motor is driving a load with a widely fluctuating torque requirement, and speed regulation is critical, then IR compensation can be adjusted to stabilize the speed from the light load to full load condition. One caution is that when IR compensation is adjusted too high it results in an increasing speed characteristic. This means that as the load is applied the motor is actually going to be forced to run faster. When this happens it increases the voltage and current to the motor which in turn increases the motor speed further. If this adjustment is set too high an unstable "hunting" or oscillating condition occurs that is undesirable.

ACCELERATION TIME

The Acceleration Time adjustment performs the function that is indicated by its name. It will extend or shorten the amount of time for the motor to go from zero speed up to the set speed. It also regulates the time it takes to change speeds from one setting (say 50%) to another setting (perhaps 100%). So this setting has the ability to moderate the acceleration rate on the drive.

A couple notes are important: if an acceleration time that is too rapid is called for "acceleration time" will be overridden by the current limit. Acceleration will only occur at a rate that is allowed by the amount of current the control passes through to the motor. Also important to note is that on most small controls the acceleration time is not linear. What this means is that a change of 50 RPM may occur more rapidly when the motor is at low speed than it does when the motor is approaching the set point speed. This is important to know but usually not critical on simple applications where these drives are used.

DECELERATION TIME

This is an adjustment that allows loads to be slowed over an extended period of time. For example, if power is removed from the motor and the load stops in 3 seconds, then the decal time adjustment would allow you' to increase that time and "power down" the load over a period of 4, 5, 6 or more seconds. Note: On a conventional simple DC drive it will not allow for the shortening of the time below the "coast to rest" time.

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ADJUSTMENT SUMMARY

The ability to adjust these six adjustments gives great flexibility to the typical inexpensive DC drive. In most cases the factory preset settings are adequate and need not be changed, but on other applications it may be desirable to tailor the characteristics of the control to the specific application.

Many of these adjustments are available in other types of controls, such as variable frequency drives.

2.3 DC DRIVES - PRINCIPLES OF OPERATION

DC drives, because of their simplicity, ease of application, reliability and favorable cost have long been a backbone of industrial applications. A typical adjustable speed drive using a silicon controller rectifier (SCR) power conversion' section, common for this type unit, is shown in Figure 2. The SCR, (also termed a thyristor) converts the fixed voltage alternating current (AC) of the power source to an adjustable voltage, controlled

direct current (DC) output which is applied to the armature of a DC motor.

SCR's provide a controllable power output by "phase angle control", so called because the firing angle (a point in time where the SCR is triggered into conduction) is synchronized with the phase rotation of the AC power source. If the device is triggered early in half cycle, maximum power is delivered to the motor; late triggering in the half cycle provides minimum power, as illustrated by Figure 3. The effect is similar to a very high speed switch, capable of being turned on and "conducted" off at an infinite number of points within each half cycle. This occurs at a rate of 60 times a second on a 60 Hz line, to deliver a precise amount of power to the motor. The efficiency of this form of power control is extremely high since a very small amount of triggering energy can enable the SCR (Silicon Controlled Rectifier) to control a great deal of output power.

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2.4 DC MOTOR CONTROL CHARACTERISTICS

A shunt-wound motor is a direct-current motor in which the field windings and the armature may be connected in parallel across a constant-voltage supply. In adjustable speed applications, the field is connected across a constant-voltage supply and the armature is connected across an independent adjustable-voltage

supply. Permanent magnet motors have similar control characteristics but differ primarily by their integral permanent magnet field excitation.

The speed (N) of a DC motor is proportional to its armature voltage; the torque (T) is proportional to armature

current, and the two quantities are independent, as illustrated in Figure 5.

CONSTANT TORQUE APPLICATIONS

Armature voltage controlled DC drives are constant torque drives. They are capable of providing rated torque at any speed between zero and the base (rated) speed of the motor as shown by Figure 6. Horsepower varies in direct proportion to speed, and 100% rated horsepower is developed only at 100% rated motor speed with rated torque.

CONSTANT HORSEPOWER APPLICATIONS

Armature Controlled DC Drives - Certain applications require constant horsepower over a specified speed range. The screened area, under the horsepower curve in Figure 6, illustrates the limits of constant horsepower operation for armature controlled DC drives. As an example, the motor could provide constant horsepower between 50% speed and 100% speed, or a 2:1 range. However, the 50% speed point coincides with the 50% horsepower point. Any constant horsepower application may be easily calculated by multiplying the desired horsepower by the ratio of the speed range over which horsepower must remain constant. If 5 HP is required over a 2:1 range, an armature only controlled drive rated for 10 (5 x 2) horsepower would be required.

Table 3 provides a convenient listing of horsepower output at various operating speeds for constant torque drives.

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Field Controlled DC Drives - Another characteristic of a shunt-wound DC motor is that a reduction in field voltage to less than the design rating will result in an increase in speed for a given armature voltage. It is important to note, however, that this results in a higher armature current for a given motor load. A simple method of accomplishing this is by inserting a resistor in series with the field voltage source. This may be useful for trimming to an ideal motor speed for the application. An optional, more sophisticated method uses a variable voltage field source as shown by Figure 6. This provides coordinated automatic armature and field voltage control for extended speed range and constant HP applications. The motor is armature voltage controlled for constant torque-variable HP operation to base speed where it is transferred to field control for constant HP-variable torque operation to motor maximum speed.

2.5 TYPES OF DC DRIVES

SIMOREG 6RA24 Siemens Variable Speed DC Drive Description & Standard Features

SIMOREG Drive Controller

The Siemens Motor Regulator (SIMOREG) is a state of the art, microprocessor based DC drive controller. This drive controller converts a three-phase, 50/60 Hz supply voltage into six pulse adjustable voltage to operate a DC motor. Output armature voltage varies directly with speed reference to provide constant torque operation from zero speed to base speed. Above base speed, the motor shunt field current may be decreased to further increase speed and provide a constant horsepower output up to maximum speed.

The SIMOREG drive controller is designed to provide precise motor speed control over a wide range of machine parameters and load conditions. This software based controller will serve well as a packaged drive or as part of a drive system.

Horsepower ranges include 1-250HP at 230VAC, 2-1750HP at 460VAC input and 1500HP and higher at 600/650V AC input. All HP ratings are available as regenerative or non-regenerative drive controllers. Listed below are standard features, a partial list of adjustments, display parameters, service conditions,

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diagnostics, and protection features. Consult the Technical Information Section for additional information.

Standard Features

The SIMOREG drive controller includes the following standard features: (Refer to the Technical Information Section for additional details.)

• Designed to meet the requirements of NEMA, IEEE, NEC, UL Listed and CSA Certified through 510A.

• 6 Pulse SCR (Silicon Controlled Rectifier) Bridge Microprocessor Control Board with 16 bit 38 MHz high performance multi- tasking microprocessor

• User interface keypad and digital display

• Power and interface control board Individual pulse transformers per SCR

• R/C snubbers across each SCR • Current transformers for current • regulator feedback • Run/Ready light • Plug-in wiring harness between

boards • Shunt field excitation circuitry

with field current loss protection and field economizing circuit

• Terminal blocks for incoming/outgoing

• wiring connections • Wire markers • Fully rated contactor • High speed AC power fuses • 460/230: 115V AC control power

Protection

• Tachometer loss and over speed • Field current loss • 12t motor overload • Instantaneous over current • Line tolerance monitoring • Phase sequence monitoring • Phase loss • dv/dt Protection on the SCR's • SCR type high speed AC line

fuses • DC output fuse on regenerative

units • Heat sink thermostat on fan

cooled units • Isolated electronics

Diagnostics There are more than 120 diagnostic messages for troubleshooting, including fault and warning indication and memory retention of the last four faults. Some of the diagnostics include:

• Line voltage out of tolerance • Line frequency unstable/out of

tolerance • Phase loss • Motor stalled • SCR failure detection and

identification • Loss of speed or voltage

feedback • Current overload • EEPROM/Microprocessor

malfunctions • Quick Stop

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transformer • Power supply transformer • Digitally fired burst type SCR

gate pulses • 1400PRV rated thyristors are

standard • Built-in AID converter accepts

external reference sources • Digital and analog tachometer

generator feedback • Serial communication via RS232

or RS485 serial ports • General purpose P-I-D loop for

additional regulation modes • Freely programmable blocks for

mathematical functions • Software programming package

to aid in start up • Peer to Peer Link • Tachometer to Voltage Feedback

switching • Four layer parameter • 5 Binary and analog outputs

Adjustments

• Priority access code protection • Minimum speed • Maximum speed • Linear acceleration • Linear deceleration • S-Curve rounding • Jog and thread speed presets • Current limit • Tapered current limit • IR compensation for voltage

feedback drives • Motor armature current rating • Motor field current rating • Self turning routine

automatically adjusts each SIMOREG drive controller to

• 8 Channel data storage

Standard Displays include:

• Speed reference • Operating speed • Current reference • Actual current • Gating angle • CEMF • Armature voltage • CEMF/Speed • RMS AC phase to phase voltage • All parameter set points • Torque direction • Operating time • Field current reference

Service Conditions

• 0-40°C Ambient • Altitude: 3300 feet above sea

level without derating (1000 meters)

• 95% Relative humidity (non-condensing)

• AC line voltage tolerance + 10%, -5%

• Frequency tolerance 48 to 62 Hz

Data Subject to Change without Notice

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optimum performance upon command

• Over speed with tachometer feedback

• CEMF crossover voltage (for field weakened speed ranges)

(a) SIMOREG 6RA70 Siemens DC Master Variable Speed DC Drive Description & Base Drive Catalog Numbers

• Description & Base Drive Catalog Numbers • Features • Design and Mode of Operation

o SIMOREG 6RA70 Converters o Parameterization Devices o Software Structure o Closed-Loop Functions in Armature Circuit o Closed-Loop Functions in Field Circuit o Optimization Run o Monitoring and Diagnosis o Functions of Inputs and Outputs o Safety Shutdown (E-STOP) o Serial Interface

(i) Description

Base Drive Description

Series 6RA70 SIMOREG DC MASTER base drive converters are complete drive assemblies ready to be installed and operated. They include a 3-phase armature converter, single-phase field converter, main contactor, protective semiconductor fuses, control power transformer, and power / control terminals.

Base drive converters are fully digital, compact units which supply the armature and field of variable speed DC drives with rated armature currents from 15A to 1660A. The motor field circuit can be supplied with DC currents of up to 40A (current levels depend on the armature rated current).

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General Information

Series 6RA70 SIMOREG DC MASTER Converters are characterized by their compact, space-saving construction. Their compact design makes them particularly easy to service and maintain since individual components are readily accessible. The electronics box contains the basic electronic circuitry as well as any supplementary option boards.

All SIMOREG DC MASTER Units are equipped with a PMU simple operator panel mounted in the converter door. The panel consists of a five-digit, seven-segment display, three LED's as status indicators and three parameterization keys. The PMU also features connector X300 with an USS interface in accordance with the RS232 or RS485 standard. The panel provides all the facilities for making adjustments or settings and displaying measured values required to start-up the converter.

The OP1 S optional converter operator panel can be mounted directly in the converter door or externally, e.g., in the cubicle door. When mounted remotely, the OP1 S can be connected to the converter with cables up to 5 meters (15 feet) length. Cable up to 200 meter (600 feet) in length can be used if a separate 5 VDC power supply is available. The OP1 S connects to the SIMOREG through connector X300 using the RS485 interface. The OP1 S can be installed as an economic alternative to conventional door mounted metering devices (Le. voltmeters, ammeters, and speed indicator).

The OP1 S features a liquid crystal display with 4 x 16 characters for displaying parameter names in plain text. English, German, French, Spanish and Italian can be selected as the display languages. In addition the OP1 S can store parameter sets for easy downloading to other drives.

The converter can also be parameterized on a standard PC with appropriate software connected to the serial interface on the basic unit. This PC interface is used during start-up, for maintenance during shutdown and for diagnosis in operation. Furthermore, converter software upgrades can be loaded through this interface for storage in flash memory.

On single-quadrant converters, a fully controlled three-phase bridge supplies the armature. On four-quadrant converters, two fully controlled three-phase bridges are connected in an inverse-parallel connection to allow both positive and negative armature current. For the field converter, a single-phase, half-controlled 2-pulse bridge supplies the motor shunt field.

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The armature and field converters can operate with AC line frequencies from 45 to 65 Hz. If required for a specific application, the frequency of the armature and field AC supplies can be different. The armature converter 3 phase AC supply is phase insensitive however on base drives rated 1180 and 1660 amperes, the 3 phase cooling fan must be connected to get the proper direction of rotation. The power section cooling system is monitored by means of temperature sensors.

The power section for the armature and field converters is constructed of isolated thyristor modules for converters rated from 15A to 850A at 460V AG-line voltage. The heat sink in this case is electrically isolated and at ground potential. On converters rated 1180 and 1660 amperes at 460 VAC, the power section for the armature circuit is constructed using disk thyristors and the heat sinks are at line voltage potential. The housing and terminal covers on power connections provide protection against accidental contact for operators working in the vicinity. All connecting terminals are accessible from the front.

All open and closed-loop drive control and communication functions are performed by two powerful microprocessors. Drive control functions are implemented in the software as program modules that can be "wired up" and changed by parameters.

Rated DC Current:

The rating plate of the converter module has 3 rated currents listed on it. The first two are IEG ratings and have no bearing on the base drive rating. The third rating is the US (NEMA) rating which the base drive rating is derived from.

The US (NEMA) rated current allows operation at rated current followed by an overload of 150% for 60 seconds in a 45°G ambient. The overload can be applied no sooner than every 10 minutes. Base drives are designed using the US rating which means that fuses, contactors, and terminal blocks are sized for the rated US (NEMA) current.

The IEG class I rating is the maximum current the power module can supply continuously with no overload. Because an overload is not possible the class I rated current is higher than the US rating. The IEG class I rating cannot be used with base drives because the base drive fuses, contactors, and terminal blocks will be overloaded.

The microprocessor calculates the current 12t value of the power section cyclically to ensure that the thyristors are not damaged in overload operation.

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Base Drive Catalog Numbers

US RATING

(Amps DC)

1-QUAD TYPE (Catalog No.)

4-QUAD TYPE (Catalog No.)

15 6RA7013-2FS22-0 6RA7013-2FV62-0 30 6RA7018-2FS22-0 6RA7018-2FV62-0 60 6RA7025-2FS22-0 6RA7025-2FV62-0 100 6RA7030-2FS22-0 6RA7030-2FV62-0 140 6RA7072-2FS22-0 6RA7072-2FV62-0 210 6RA7075-2FS22-0 6RA7075-2FV62-0 255 6RA7077-2FS22-0 6RA7077-2FV62-0 430 6RA7082-2FS22-0 6RA7082-2FV62-0 510 6RA7083-2FS22-0 6RA7083-2FV62-0 850 6RA7087-2FS22-0 6RA7087-2FV62-0

1180 6RA7091-2FS22-0 6RA7091-2FV62-0 1660 6RA7094-2FS22-0 6RA7094-2FV62-0

1000Hp DC DRIVE

The drive system will consist of one -1660 ADC/750 VDC six pulse drive cabinet. The power converter, SCR (Silicon Controlled Rectifier) heat sink bridges and High Horsepower command modules (6RA70) are manufactured by Siemens. Siemens control and firing technology is applied for superior operation of SCR gating, current, speed and monitoring of motor drive. Overload current limit is 150% for 1 min. every 10 min.

The following features are included:

• One - modified Nema 12, two door cabinet. Mild steel construction measuring (90"x78"x30"). Paint is factory standard, ANSI 61 Gray.

• One - 2000 Amp. Molded Case Switches mounted w/ through the door manual switch handle (pad lockable).

• One - 1660 ADC 1-Quadrant SCR bridge assembly.

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• SCR AC line fusing. • One - cabinet air cooling and filtration package. • One - 85 ADC, single phase, Siemens field module and transformer. • Customer supplied encoder feedback speed control as per customer

drawings. • One - main motor blower circuit 20 HP @ 600V Max. • Three digital meters for the following: Armature Amps, Armature Volts

and Field Amps. Meters are mounted in the Master drive cabinet door. • Siemens door mounted programming and fault indication keypad. • Door mounted Hand/Off/Auto selector switch. • Copper pad bus areas for incoming and out going AC/DC power

connections.

OPTIONAL ISOLATION TRANSFORMER

(1) 1500 KVA with the following specifications:

• Primary Voltage 25 KV, 60 Hertz, 3 phase Delta, 1500 KVA • Secondary Voltage 600/347 Wye, 1500 KVA • Aluminum windings, 150 Deg. C rise, 220 Deg. C Insulation • K-Factor 9 • Nema 1 enclosure, floor mount

3000Hp DC DRIVE

The drive system will consist of two - 2400 ADC / 750 VDC six pulse drive cabinet sections. The power converter SCR (Silicon Controlled Rectifier) heat sink bridges are manufactured by Joliet Technologies and are fitted with Siemens High Horsepower command modules (6RA70). Siemens control and firing technology is applied for superior operation of SCR gating, current, speed and monitoring of motor drive. Each of the 2400 ADC sections work together by load sharing the high current demand. The drives will be designated as Master / Slave. By supplying each section with a single isolation transformer with two outputs Delta & Wye, we can minimize the harmonic distortions caused by SCR type converter drive systems. The overload current limit rating is 150% for 1 min. every 10 min.

The following features are included:

• Two - two door, modified Nema 12 cabinets, Mild steel construction measuring (90"x78"x30"). Paint is factory standard, ANSI 61 Gray.

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• Two - 2500 Amp. Molded Case Switches mounted w/ through the door manual switch handle (pad lockable).

• Two - 2400 ADC 1-Quadrant SCR bridge assemblies. • Two Sets - SCR AC line fusing. • Two - cabinet air cooling and filtration packages. • Two - Siemens High HP command modules. • One - 85 ADC/single phase, Siemens field module and transformer. • Customer supplied encoder feedback speed control as per customer

drawings. • One main motor blower circuit 20 HP @ 600V Max. • Three digital meters for the following: Armature Amps, Armature Volts

and Field Amps. Meters are mounted in the Master drive cabinet door. • Siemens door mounted programming and fault indication keypad. • Door mounted Hand/Off/Auto selector switch. • Copper pad bus areas for incoming and out going AC/DC power

connections.

DCS 400 Digital DC Converter 20 to 1000A DC

Introducing the world's most competitive DC package

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ABB has developed a user-friendly drive system package (DCS 400, DMI Motor) to meet the demands of machine builders.

Our aim is to offer the best combination of reliable products at the most affordable price, backed by on-time delivery, good partnership and fast response to inquiries. At the heart of the drive package is the DCS 400 - a new generation of DC drives specifically designed to meet the ever-changing needs of machine builders.

"Total ease of use" was the foundation of this drive's development. The result is a drive that is:

• as easy to handle as an analog drive yet incorporates all of the features of a digital drive.

• easy to design into machine equipment, with just the right amount of features.

• easy to install and set-up, even by those without special drives experience.

Small Design

The DCS 400's compact design brings substantial space savings to machine builders, allowing them to integrate more accessories within the same space.

• Existing DC drives are easily replaced with the DCS 400.

• At only 103.4 in (270 mm) wide, and with all the power cabling located at the base of the drive rather than the side, two DCS 400 units can be installed inside the

Technical Features

• Digital 6-pulse converter • 10 - 600 Hp (10 - 448 kW) • 20 to 1000 A DC • Input Voltage from 230 to 500

V, 50/60 Hz • Nonregenerative & regenerative

drives available • IGBT - field supply for field

weakening is included

Supply Voltages Power and Field:

230 - 500 VAC, 3-phase

Input Frequency:

50 - 60 Hz

Converter Fan: 115/230 VAC, single-phase

Control Power:

115/230 VAC, single-phase

Control I/O Digital Inputs: Eight (8), 24 VDC Digital Outputs:

Four (4), 24 VDC One (1) relay

Analog Inputs: Two (2), ±10 VDC, 12 bit

Analog Outputs:

Two (2), ±10 VDC, 12 bit

Power Spectrum, 2Q, Non-Regenerative

ModuleType

Armature Current Range

(A)

Field Current

(A) kW HP

A1 20, 45, 65, 90, 125 0.1 to 6 12 to

73 10 to

75 A2 180, 230 0.3 to 104 to 100 to

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same 233.4 in (600 mm) cabinet. • The field supply, including the

fuse and choke, are integrated into the DCS 400, further contributing to its small size and simplicity of design.

• No need for a field voltage adaptation transformer to match the line supply voltage with that of the motor. The DCS 400 uses fewer components, leading to both smaller size and greater reliability.

12 133 125

A3 315, 405, 500

0.3 to 14

183 to 290

175 to 300

A4 610, 740, 900

0.3 to 20

354 to 402

350 to 539

Power Spectrum, 4Q, Regenerative

ModuleType

Armature Current Range

(A)

Field Current

(A) kW HP

A1 25, 50, 75, 100, 140 0.1 to 6 13 to

73 10 to

75

A2 200, 260 0.3 to 12

104 to 135

100 to 150

A3 350, 450, 550

0.3 to 14

182 to 290

200 to 300

A4 680, 820, 1000

0.3 to 20

354 to 448

400 to 600

The total integrated package for machine builders Fieldbus Adapters Multiple serial communication options allow integration with higher level control systems.

DC Converters DCS 400 6-pulse converters offer accurate torque and speed control in the low power range. Simplicity of operation is a hallmark of the drive.

DC Motors ABB's family of DC motors offer a compact, modular design, combined with low vibration and noise levels as well as high output and energy efficiency.

Speed Feedback A variety of speed feedback devices can be used with PowerPack and are standard features of the DCS 400.

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The user is guided through the commissioning procedure by following simple steps that are outlined by the alpha-numeric control panel.

An alternative to the control panel is ABB's PC-based program, Drive Window Light, used for guided on-line commissioning, including:

• Parameter setting • Reference display and feedback

values • Trending • On-line help files

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The easiest drive to install...

(b) Reduced Wiring

By fully integrating the field supply, ABB's engineers have been able to patent a design with three wires in and four wires out, reducing wiring and requiring less installation time.

Fast and Easy Installation

ABB's DCS 400 cuts costs and installation time by incorporating the following features:

• A simple, step-by-step installation guide • Bottom plate cable entry, providing rapid and easy access to power

terminals • Easy to access I/O connection points via bottom cover plate • The drive's ability to operate directly on any worldwide voltage from 230 -

500 V, 50/60 Hz main, 115 - 230 V aux.

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The fastest drive to commission...

(c) Commissioning Wizard

The DCS 400 is the first digital drive which can be commissioned without special knowledge of drives. More importantly, the commissioning and start-up time is dramatically faster than that of other DC drives.

• The wizard uses either the drive's control panel or ABB's commissioning tool, Drive Window Light, which is based on RS232 communications using a standard plug (see illustration above).

• Once the motor and process data have been entered into the drive, the user is guided through commissioning using the self-tuning functions for armature current, speed, flux and field current.

• No additional documentation or hardware is needed to commission the DCS 400.

• Application macros that require setting only a few user-selectable parameters make the commissioning of specific applications easier compared to the several hundred parameters that must be set with other DC drives.

Module Type

Height in (mm)

Depth in (mm)

Width in (mm)

A1 12-1/2 (310) 8 (200) 10-3/4

(270)

A2 12-1/2 (310)

10-3/4 (270)

10-3/4 (270)

A3 15-3/4 (400)

12-1/2 (310)

10-3/4 (270)

A4 23 (580) 13-3/4 (345)

10-3/4 (270)

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4.0 RECOMMENDATIONS

A new generation of variable speed drives:

The Hanover Messe saw the launch of the new generation of Emotron AB variable speed drives, which have grown in terms of function but reduced in size, with a new application focus

The Hannover Messe saw the launch of the new generation of Emotron AB variable speed drives, which have grown in terms of function but reduced in size. At the same time the company presented its new strategy of focusing on selected applications. This allows cutting edge knowledge and products adapted to specific needs.

The new Emotron FDU is developed for applications such as pumps, fans, compressors and blowers, while Emotron VFX is adapted for dynamic applications such as cranes, crushers and mixers.

Increased functionality in a smaller format.

The Emotron new variable speed drives, FDU and VFX in the 0.75-1,500 kW output range, offer efficient, reliable and user-friendly control.

Among the new features are.

* An integrated shaft power monitor that detects deviations from normal operation over the whole speed range.

This prevents unplanned downtime and allows preventive action before energy is lost or equipment damaged.

* New compact I/O boards allow connection of up to four options, for example communication, pump control and crane control.

Virtual connection of logic functions, comparators and timers means that more options can be used.

Different logical functions can be combined without cables or external I/Os.

* Integrated temperature control offers more efficient motor protection and extends equipment lifetime.

PTC and PT100 sensors can be connected for motor protection and process feedback without transmitters.

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Encoder can be connected for more accurate speed control in dynamic applications.

* Operating parameters are set in selectable process units, which make monitoring simpler and safer.

The control panel is removable and can easily be moved between variable speed drives to copy settings.

* The installation is simple and cost effective due to IP54 enclosure and extremely compact format even for high outputs.

Liquid cooling is available as an option, which saves space and energy because air conditioning is not required.

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5.0 CONCLUSIONS

DC drives consist of an SCR (Silicon Controlled Rectifier) bridge, which converts incoming three or single-phase AC volts to DC volts. During this conversion process DC drives then can regulate speed, torque, voltage and current conditions of the DC motor. This is ideal for industrial processes such as tube mills, extruders, mixers, paper machines and various other controlled applications. Joliet Technologies can provide several DC Drives from different reputable manufactures. Packages can vary from Onsite Retrofits to custom multi drive cabinets.

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Engineering and Integration

Solutions that may be helpful consist of:

• Sizing a drive to a target horsepower, current and voltage required. • Power and harmonics issues can be addressed and corrected through the use

of isolation transformers, reactors and filter packages. • Customizing control and analog circuitry to be integrated in with existing

engineered specifications. • Operator consoles / Door mounted pilot and metering devices • MCC and Switchgear installation type custom packaging for growing

demands of the industry. • Peer to Peer and Master/Slave drive configurations for Follower and High

Horsepower applications. • Engineered cabinet cooling system for any environment. Today's drives are

more compact and can be placed in smaller enclosures only if the correct cooling is applied.

• Communication Systems for advanced Modbus, Profibus and Data HighWay linking multiple devices such as power management and HMI/PLC systems.

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4.0 REFERENCES

1. www.electricmotors.machinedesign.com

2. www.adcmotors.com

3. www.dcmotorsinc.com

4. www.grainger.com/production/info/dc-motors.htm

5. www.orientalmotor.com/products/ac-dc-speed-motors/index.htm

6. www.processingtalk.com/indexes/categorybrowsedo.html

7. www.axiomatic.com/