ACDC drives

7/30/2019 ACDC drives

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The DC Drive

In the beginning


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6 Basic Adjustments

Speed Reference Minimum Speed Maximum Speed Acceleration Deceleration Current Limit


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Typical DC Drive

Adjustments


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Adjustments - Speed Reference

Speed Reference Typically it is a potentiometer that an operator

turns to adjust the speed of the machine.


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AdjustmentsMin. Speed

Minimum Speed How fast the machine will operate with the Speed

Reference turned all the way DOWN.


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AdjustmentsMax. Speed

Maximum Speed How fast the machine will operate with the Speed

Reference turned all the way UP.


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Adjustments - Acceleration

Acceleration Rate How much time it will take to go from stop to full

speed.


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Adjustments - Deceleration

Deceleration Rate How much time it will take to go from full speed to

stop.


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Adjustments - Current Limit

Current Limit This limits the amount of current coming out of the

drive. Its based on the motors Full Load Amps.


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Basic DC Drive Operations

Speed Reference - How fast you want themachine to go.

Can be analog 0 - 10vdc or 4 - 20mA signalfrom a controller.

Can also be a adjustment via parameter,network data or keypad input

Signal is modified by Min. and Max. SpeedAdjustments Goes to the Ramp Circuits


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Basic DC Drives Operations

Ramp (Rate) circuits get the speed referenceand ramps the signal up over a period of

time.

The time periods are adjustable via a pot,parameter or network data.

Output goes to a summing junction.


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Summing Junction Takes the signal from the Ramp circuits and adds

them together with some sort of feedback.

Feedbacks can be speed,voltage or current. The result out of the summing junction is an error

signal indicating the difference between the speed

reference and the feedback. Another way to look

at it is difference between how fast I want it to goverses how fast it is actually going

Output goes to the Major Loop (Speed or Voltage

Loop)


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Major Loop Operational Amplifier (Loop 2) The speed error signal from the summing junction

is the input. This amplifies the error signal.

There is a feedback loop around the amplifier.This loop has a resister and capacitor (digital

drives would be integrator and proportional

response)

Tuning these values of the feedback loop willaffect the overall response (stability) of the drive.


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Stability


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Second Summing Junction The input to this junction is the amplified error

signal out of the Major Loop (Loop 2) operational

amplifier. The signal is now called CurrentReference.

Current Reference is Summed together with the

current feedback signal.

The output signal goes to the Current Minor Loop(Loop 1) Operational Amplifier.


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Current Minor Loop (Loop 1) The current error signal from the summing

junction is the input. This amplifies the error

signal.

There is a feedback loop around the amplifierwhich is a resistor and capacitor. (Digital

drives is Integrator & Proportional response) Tuning these values will affect overallresponse (stability) of the drive.


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Basic DC Drives Operations

Gate Pulse Driver Circuits These circuits provide the pulse to the gate inputs

on all the SCRs. Input from CML.

Everything in the drive up to this point is there totell these circuits when to fire.


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Gate Pulse Timing


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Power Module This is where the SCRs live.

The Power Module has AC power connected to it

which is what gets switched (through the SCRs)to the motor armature circuit as DC.


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SCR Construction


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Typical DC Drive - SCRs


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Power Module (SCRs)

Non-Regen


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Power Module (SCRs)

Regen


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Motor The interaction of 2 magnetic fields causes

rotation (armature & field).

Typically the Field coils have a constant voltageapplied and we vary the voltage in the armature to

get variable speed (up to Base speed)

To go above base speed we have constant

maximum voltage in the armature and then weweaken the field voltage.


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Speed Regulator


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Voltage Regulator


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Current Regulator


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Position Regulator


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Force Transducer

Tension Regulator Basic


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Contactor Reversing


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3 Basic Types of Braking

Coast to Rest Dynamic Braking Regenerative Braking


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Braking Methods

Coast to Rest The application coasts to a stop. Time to rest is

determined by Friction, Windage and Inertia of the

load. Dynamic Braking

Inertia contained in a load causes the load to

continue rotating generating a voltage and current

in the armature circuit opposite in direction ofmotoring and being dropped across a high

wattage resistor.


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Braking Methods

Regeneration Inertia contained in a load causes the load to

continue rotating generating a voltage and current

in the armature circuit opposite in direction ofmotoring current. Using a second set of SCRs

connected opposite than the first set, these are

fired so that current flow is allowed to flow in the

opposite direction back to the AC line supply.


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4 Quadrant Operations


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DC Dynamic Braking


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Braking Force


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Stopping Methods Compared


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The AC drive

Then there was AC


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AC Drive Power Section

Motor

AC Line

InverterInputrectifier

Filter


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PWM waveform is a series of repetitive Voltage pulses

1

3

+ DC Bus

- DC Bus

VLL @ Drive500 Volts / Div.

Phase Current10 Amps / Div.

M2.00 s Ch1 1.18V


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NEMA Enclosures For Drives

NEMA TYPE 1 - General Purpose Indoor, Nonvent &

Ventilated

Designed for use indoorsIntended for areas where no unusual service conditions exist (relatively

clean/dry)

Prevent accidental contact with the enclosed equipment

Panels are louvered and not sealed/gasketed

Provide good protection against falling dirt


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NEMA TYPE 1 - General Purpose Indoor, Nonvent &

Ventilated

5 HP SP500 w/Mains FilterFlexPak 3000 w/NEMA 1 Enclosure


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NEMA TYPE 4 - Water-tight/Dust-tight, Indoor/Outdoor

NonventilatedIntended for use indoors to protect against:

Splashing water

Falling or hose-directed water

Seepage of water

Severe external condensationMust have conduit hubs for water-tight connection at conduit entrance

Mounting method must be external to equipment cavityNo louvers, no ventilated openings


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NEMA TYPE 4 - Water-tight/Dust-tight, Indoor/Outdoor

Nonventilated

Gaskets on doors

NEMA Type 4X are also corrosion-resistant

NEMA 4/12 1 HP MinPak PlusSP500


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NEMA TYPE 12 - Dust-tight/Drip-tight, Indoor

Nonventilated

Suitable for indoor industrial applicationsDesigned to protect against:

Fibers wFlyings wLint

Dust wDirt wLight splashings

Seepage wDrippings

External condensation of noncorrosive liquids

All holes/conduit openings must have oil-tight gaskets and use oil-tight or dust-tight mounting mechanisms


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Nonventilated

Doors must have oil-resistant gasketsMounting method must be external to equipment cavity

Enclosures must have captive closing hardware and provision for locking

Reliance often times combines Type 4 with Type 12 to make a versatile NEMA

4/12 (water/dust) enclosure


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Nonventilated

Type 4/4X/12 Type 12Type 4X/12


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Open Loop AC

Cl d L AC


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Closed Loop AC

Vector


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Open Loop SensorLess

3 C t f V t


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TorqueCurrent

MagnetizingCurrent

Motor

Current

3 Components of Vector

Control


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TorqueCurrent

Magnetizing Current

Motor

Current

90 Degrees

Torque is optimized by maintaining Magnetizing & Torque Current @ 90 degrees

Optimizing Torque output


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Identified during Auto-tuning

Typically ranges from 30%- 50% of Motor FLA

Fixed from 0% to 95% of Motor Base RPM

Proportionally decreased in Field Weakening Range

95% MotorBase RPM

Motor Base RPM

Fixed @ 30% - 50% FLA

Magnetizing Current is decreasedin the Field Weakened area

Magnetizing Current


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Represents the actual load at the motor shaft

Current demand above Magnetizing is Torque

95% Motor Base RPMMotor Base RPM

Torque Current varies from Magnetizing to Max FLA

Magnetizing Current is fixed Mag. Current is decreased

Torque Current


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The vector sum of Magnetizing and Torque Current

Regulated by internal current feedback

95% Motor Base RPM Motor Base RPM

Torque Current varies from Magnetizing to Max FLAMotor Currentis the sum ofMagnetizing

and Torque

Magnetizing Current is fixed Mag. Current decreases

Motor Current


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General Purpose Mode V/Hz


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Vector Mode Torque Curve


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Constant Torque Load


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Variable Torque Loads


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AC Snubber Braking


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AC Regeneration

Transportation Application


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Transportation Application

Matrix

Metals Application


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Metals Application

Matrix


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Paper Application


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Paper Application

Matrix


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Consumer Application


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Consumer Application

Matrix


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Gas/Oil/Mining Application


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Gas/Oil/Mining Application

Matrix


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THE END


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Notes


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Notes


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Notes


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Notes

N t


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Notes

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ACDC drives