ROTATING ELECTRICAL MACHINE LAB

B.E. 5th Semester

DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING

EXPERIMENT NO:-01

Starting of single phase Induction motor.

AIM:-TO determine the performance characteristics of a single phase capacitor start Induction motor by conducting load test.

NAME PLATE DETAILS:-

Type of I.M. Capacitor start Voltage Current Speed Power

APPARATUS REQUIRED:-

S.N. Apparatus Range Type Quantity 1. Voltmeter 0-300V M.I. 1 2. Ammeter 0-10A M.I. 1 3. Wattmeter 300V,10A 1 4. tachometer Digital 1 5. Connecting wire

THEORY:- When the split-phase rotating field was described, it was pointed out that the phase difference between start and run winding currents falls far short of 90 degrees. The starting torque developed in a motor that uses a split-phase stator also falls far short of the maximum that can be attained at an ideal 90 degree phase difference. A phase shift closer to the ideal 90 degrees is possible through the capacitor-start system for creating a rotating stator field. This system, a modification of the split-phase system, uses a low reactance capacitor placed in series with the start winding of the stator to provide a phase shift of approximately 90 degrees for the start current. This results in greatly improved starting torque over the standard split-phase system. Capacitor start motors have the same running characteristics as their splitphase counterparts. The capacitor and the start winding are disconnected by a centrifugal switch,just as in the case of the standard split-phase motor. Reversing the direction of rotation of a capacitor start motor is the same as in the case of the split-phase motor; that is, reverse the connections to the start or to the running winding leads. Single-phase motors are all rather noisy because they vibrate at 120Hz when operated on a 60Hz power line. Various attempts to reduce this noise such as resilient rubber mounting are never totally effective in eliminating this vibration, particularly when the motor is directly coupled to a large resonant-prone fan.

CIRCUIT DIAGRAM:-

PROCEDURE:- 1.connectoin are given as per we circuit diagram. 2.switch on the supply at no load condition. 3.Apply the rotor voltage to the motor using the varial and note down the reading at ammeter and wattmeter. 4.Vary the load in suitable steps and note down all the meters reading till fill bad condition. PROCEDURE FOR GRAPH:- 1.O/P power vs speed. 2.O/P power vs torque. 3.O/P power vs effecincing. 4.O/P power vs slip. 5.O/P power vs power factor. FORMULA USED:- 1.torque T=(S1~S2)*9.81*R Nm 2.output power =2*pi*NT/60 W 3.effencicy n%=(o/p power/i/p power)*100 4.slip S%=(Ns-N/Ns)*100 5.power factor cos$=W/VI CALCULATION:-

OBSERVATION TABLE:- S.N. VL(VOLT) IL(AMP) SPEED

N(RPM) S1 (Kg)

S2 (Kg)

Torque T(Nm)

Wattmeter reading

Output Power

Effic.n%

p.f.

GRAPH:-

PRECAUTION:- 1. Before switching on the supply the variac is kept in minimum position. 2. Initially these should be on no load while starting the motor. APPLICATION:- Used in Fan , Rolling mill , Reversible drive. RESULT:- Thus the load test on the single phase induction motor has been successfully conducted and its performance characteristics determined.

VIVA QUESTION 1. What is the relation between o/p power and efficiency in load test of induction motor.

ANS- Straight then saturation point parabolic 2. Name the motor being used in a ceiling fan

ANS-Split phase capacitor start induction motor 3. Does a shaded pole induction motor have a much starting torque

ANS- No, it has a little starting torque 4. What is universal motor

ANS-A universal motor is a series wound motor. 5. Does the capacitor start induction motor has a low or high starting torque

ANS-Has a high starting torque 6. What is the two types of universal motor

ANS- permanent-magnet type & variable reluctance type 7. Where is stepper motor used

ANS-Industrial purpose 8. How can the direction of capacitor run induction motor be reversed

ANS-By reversing the leads of Auxiliary winding or main winding but not both 9. What is the purpose of this practical

ANS-To determine the performance c/s of single phase induction motor 10. What is slip

EXPERIMENT NO:-02 Regulation of three phase alternator by EMF & MMF method OBJECT:-To perform the regulation of three phase alternator by EMF and MMF methods and also draw the vector diagram. NAME PLATE DETAILS:- Voltage 415V Current 3.5A Speed 1500rpm Power 3Hp APPARATUS REQUIRED:- S.N. Apparatus Type Range Quantity 1. Ammeter M.C. 0-5A 1 2. Ammeter M.I. 0-10A 1 3. Voltmeter M.C. 0-10V 1 4. Voltmeter M.I. 0-600V 1 5. Rheostat W.W. 250 ,1.5A 1 6. Rheostat W.W. 1200, .8A 1 7. tachometer Digital 1 8. TPST knife switch THEORY:- The regulation of three phase alternator may be performed by conducting the open circuit and the short circuit tests. The methods employed for determination of regulation are EMF or Synchronous impedance method, MMF or Ampere turn method and the Zero power factor method or Poltier triangle method. In this experiment the EMF & MMF methods are used. The OC and SC graphs are plotted from the two tests. The synchronous impedance is found from the OC test. Regulation is determined at different power factor by calculations using vector diagram. The EMF method is also called pessimistic method as the regulation obtained is much more than the actual value. The MMF method is also called optimistic method as the value of regulation obtained is much less than the actual value. In the MMF method the armature leakage reactance is treated as an additional armature reaction. In both methods OC & SC data are utilized.

CIRCUIT DIAGRAM:-

PROCEDURE:- For both EMF and MMF method-

1. Note down the name plate details of the motor and alternator. 2. Connection are made as per the circuit diagram 3. Switch ON the supply by using DPST switch. 4. Using the 3 point starter start the motor to run at the synchronous speed by adjusting

the motor feld rheostat. 5. Conduct open circuit test by varying the potential divider for various value of field

current and tabulate the corresponding open circuit voltage reading. 6. Conduct short circuit test by closing the TPST switch and adjust the potential divider to

set the rated armature current and tabulate the corresponding field current. 7. The stator resistances per phase is determined by connecting any one phase stator

winding of the alternator as per the circuit diagram using M.C. voltmeter & ammeter of suitable reading.

PROCEDURE TO DRAW GRAPH FOR EMF METHOD:- 1. Draw the open circuit characteristics (Generated voltage per phase v/s field current) 2. Draw the short circuit characteristics curve (Short circuit current v/s field current)

3. From the graph find the open circuit open circuit voltage per phase for rated short circuit current Isc

4. By using respective formula find the Zs , Xs , Eo and percentage regulation. PROCEDRE TO DRAW GRAPH FOR MMF METHOD:-

1. Draw the open circuit characteristics curve (Generated voltage per phase v/s field current)

2. Draw the short circuit characteristics curve (Short circuit current v/s field current) FORMULA:-

1. Armature resistance Ra 2. Synchronous impedance Zs = (OC voltage/SC current) 3. Synchronous reactance Xs =(Zs2 Ra2)1/2 4. Open circuit voltage for lagging power factor = { (VCOS +IaRa)2 + (VSIN + IaXS)2}1/2 5. Open circuit voltage for leading power factor = { (VCOS +IaRa)2 + (VSIN - IaXS)2}1/2 6. Open circuit voltage for unity power factor = { (V +IaRa)2 + (V + IaXS)2}1/2 7. Percentage regulation = (Eo V)/V * 100

CALCULATION:- OBSERVATION TABLE:- For OCC Test S.N. If (Amp) Voc (Volt) Vg (Volt ) 1. 2. 3. 4. For SCC Test S.N. If (Amp) Ia (Amp)

GRAPH:-

PRECAUTION:- 1. Before switching on the supply the variac is kept in minimum position. 2. Initially these should be on no load while starting the motor. RESULT:- Thus the regulation of three phase alternator has been predetermined by EMF and MMF method.

VIVA QUESTION 1. What will be the number of pole of a 5o Hz alternator if it run at its greatest speed

ANS- two 2. Name the two types of alternator

ANS- Salient pole type And smooth cylindrical type 3. What is the maximum speed of 50HZ alternator

ANS- 3000rpm 4. At what voltage field of alternator is usually excited

ANS- 125 or 250V 5. What is other name of distribution factor

ANS- Breadth factor 6. Which one is pessimistic method

ANS-MMF method 7. In case of turbo alternator rotor I made of

ANS-Forged steel 8. Alternator operates on the principle of

ANS- Electromagnetic induction 9. In a synchronous machine, the stator frame is made of

ANS-Cast iron or welded steel plates 10. Hydro generator are generally employed to run at

ANS-500rpm

EXPERIMENT NO:-03 Determination of Xd & Xq of synchronous machine AIM:- To determine the value of Xd & Xq of the given salient pole synchronous machine NAME PLATE DETAILS:- Voltage 415V Current 3.5A Speed 1500rpm Power 3Hp

APPARATUS REQUIRED:-

S.N. Apparatus Range Type Quantity 1. Ammeter 0-5A M.I. 1 2. Rheostat 250/1.5A W.W. 1 3. Tachometer 0-5000rpm Digital 1 4. Voltmeter 0-300V M.I. 1 5. Phase Square 500V ----- 1 6. Auto Tran. 415V/0-470V W.W. 1 7. Fuse 5A 3

THEORY:-The value of Xd and Xq are determined by connecting the slip test. The synchronous machine is driven by a separate prime mover at a speed slightly difference from the synchronous speed. The field winding is left open and positive sequence balanced voltage of reduced and rated frequency and impressed across the armature terminal. Here the relative velocity between the field poles and rotating armature MMF wave is equal to the difference between synchronous and the rotor speed that is slip speed ,when the rotor is along the d-axis ,now it has a position of minimum reluctance ,minimum flux leakage & maximum flux produced links with the winding then Xd = (max. armature terminal voltage/minimum armature current)

As the current is small then Vi will be high as drop will be small when the rotor is along q-axis. Then it is maximum, the flux leakage would be max ,then the min flux produced links with winding so max EMF

Xq = (min armature terminal voltage per phase/max armature current per phase)

CIRCUIT DIAGRAM:-

PROCEDURE:-

1. Give all connection as per the circuit diagram. 2. Run the machine at synchronous speed and give a small voltage. 3. Check the phase sequence of the machine with the incoming external supply. 4. Now remove the supply for field winding below the rated speed. 5. Apply the external supply slowly and observe the oscillation in ammeter & voltmeter. 6. Note the maximum and minimum voltage and current.

FORMULA:-

Xd = Vmax/Imin

Xq = Vmin/Imax

CALCULaATION:-

OBSERVATION TABLE:-

S.N. Vmax Vmin Imax Imin

PRECAUTION:-

1. Check the phase sequence of the machine with that of external supply before closing the switch.

2. Disconnect the excitation supply of the alternator while giving the external supply. 3. Slip should be made as small as possible.

RESULT:- The value of Xd and Xq are determined.

VIVA QUESTION

1. By which type of test Xd and Xq are determined. ANS-Slip Test

2. How the Xd and Xq are calculated. ANS- Xd = Vmax/Imin Xq = Vmin/Imax

3. Which type of ammeter are required for this experiment ANS-Moving Iron type

4. Which type of alternator are preferred in this experiment ANS- Salient pole rotor type alternator

5. Number of poles of this alternator ANS- Two poles

6. It is possible to make a balanced 3 phase , 6 pole winding with 48 slots ANS- NO, m = 48/(3*6) = 8/3

7. What are the losses that take place in an alternator ANS-Electrical losses , core loss, Friction loss, Stray power loss

8. Which losses is under electrical losses ANS-Armature winding loss ,brush contact loss, field loss

9. What is an air gap line ANS- Tangent to OCC is called the air gap line

10. What parameter of load influence the armature reaction of an alternator ANS- Power factor of load

EXPERIMENT NO:04

V and Inverted V curve of synchronous motor

AIM:- TO draw the V and inverted V curve of three phase synchronous motor.

NAME PLATE DETAILS:-

Voltage 415V Current 3.5A Speed 1500rpm Power 3Hp

APPARATUS REQUIRED:-

S.N Apparatus Type Range Quantity 1. Ammeter M.I. 0-5A 2 2. Ammeter M.C. 0-2A 1 3. voltmeter M.I. 0-600V 2 4. Rheostat 200 15A 2 5. Wattmeter UPF 600v ,5A 2

THEORY:-In case of synchronous motor driving a constant mechanical load variation in field or DC excitation will not only affect the power factor but also the current drawn by the motor. Except for change in copper losses due to variation in armature current and slight change in core losses due to variation in flux , the power input to the motor is almost constant for a constant load.

CIRCUIT DIAGRAM:-

PROCEDURE:-

1. Note down the name plate details of the motor 2. Connection are made as per circuit diagram 3. Switch ON the TPST 4. By adjusting the Auto transformer from the minimum position to maximum position the

supply is given in position-1 5. Start the motor by keeping the mode of starter on position-1 6. By changing the position of stator mode-2 apply the excitation to the stator 7. Note down the reading of voltmeter ,Ammeter and wattmeter 8. Repeat the above procedure for excitation 9. Finally plot the graph for V and inverted V curve

OBSERVATION TABLE:-

S.N. Excitation current

Armature current

Power factor W1 W2

GRAPH:-

PRECAUTION:-

1. The potential barrier should be in maximum position. 2. The motor should be started without load 3. Initially TPST switch is in open position.

APPLICATION:-It is use to determine the power factor of alternator and synchronous motor.

RESULT:- V and inverted V curve are drawn

VIVA QUESTION

1. Under short circuit condition, the power factor of alternator ANS-Almost zero lagging 2. Value of load angle when the power output of a salient pole synchronous generator is

maximum ANS-Not depend 3. Magnitude of field flux always remain constant ANS- Yes 4. What is condition for armature MMF , air gap flux and field MMF ANS- The armature MMF leads the air gap flux and this leads the field flux 5. Starting torque of 3 phase synchronous motor ANS-No starting torque

EXPERIMENT NO:05

Load test on three phase squirrel cage induction motor

AIM:-To draw the performance characteristics of three phase squirrel cage induction motor by conducting load test.

NAME PLATE DETAILS:-

Type of I.M. Squirrel cage Voltage 415V Current 4.7A Speed 1400rpm

APPARATUS REQUIRED:-

S.N

Apparatus Type Range Quantity

1. Ammeter M.I. 0-5A 1 2. voltmeter M.I. 0-600V 1 3. Wattmeter UPF 600v ,5A 2

Tachometer Digital 1 Auto Trans. 1

Theory:-The three phase induction motor consist of stator and rotor with the other associated parts in the stator. The three phase winding is provided. The winding of three phase is displayed in phase by 1200 A three phase squirrel cage is fed to the three phase winding , these winding produced a resultant magnetic flux and it rotate in phase like a solid magnetic pulse being rotate magnetically.

CIRCUIT DIAGRAM:-

PROCEDURE:-

1. Connection are given as per circuit diagram 2. Three phase induction motor is started with Auto transformer 3. If the pointer of one of the wattmeter reading reverse, interchange the current coil

terminal and take the reading 4. The motor is loaded step by step till we get the rated current and the reading of the

Voltmeter, Ammeter, Wattmeter ,Spring balance are taken.

FORMULA:-

Cos =cos(tan-13{(W1-W2)/(W1+W2)} CALCULATION:-

OBSERVATION TABLE:- S.N.

Load current IL

Load voltage VL

Wattmeter W1 W2

Input power W1+W2

Speed N

Spring S1 S2 S3

Torque

O/p power

Effi

Slip p.f. cos

GRAPH:-

PRECAUTION:- 1. The potential barrier should be in maximum position. 2. The motor should be started without load 3. Initially TPST switch is in open position.

APPLICATION:- Hence by load test we can determine the loading capacity of squirrel cage induction motor.

RESULT: Thus the performance characteristics of three phase squirrel cage induction motor by conduction load test has been completed

VIVA QUESTION

1. In induction motor shaft is made of ANS-Mild steel 2. The rotor of three phase squirrel cage induction motor ANS- Rotor conductor are short circuited through end rings 3. What is the purpose of blades in s. cage induction motor ANS-Facilitate cooling o rotor 4. In slip ring I.M. if the rotor is delta connected stator must be connected in ANS-Star 5. If the induction motor is uneven air gap then it causes of ANS-Heating of motor, Unbalancing of motor shaft 6. If the air gap is smaller what happen in three phase I.M. ANS-Reduce the magnetizing current 7. If the air gap is increased what happen ANS-Power factor will reduced 8. Starting torque of three phase I.M. related to supply ANS-V2 9. Which type of starting torque in S. cage I.M. ANS-Slightly more than full load torque 10. Starting torque will be maximum when ANS- R2 = X2

EXPERIMENT NO:06 Speed control of three phase slip ring Induction motor

AIM:-To conduct the speed control test on 3- slip ring Induction motor NAME PLATE DETAILS:- Type of I.M. Squirrel cage Voltage 415V Current 4.7A Speed 1400rpm APPARATUS REQUIRED:- S.N Apparatus Type Range Quantity 1. Ammeter M.I. 0-1A 1 2. voltmeter M.I. 0-600V 1 3. Connecting

wire As per

required THEORY:- These motor are practically started with full line voltage applied across the stator terminal ,the value of starting current is adjusted by adjusting the variable resistance in the rotor circuit . The controlling resistance in the rotor circuit is fine gradually cut after the rotor has got allotted speed. It has been already shown by decreasing rotor resistance .at the same time starting torque is also increased due to the improvement in power factor. CIRCUIT DIAGRAM:-

PROCEDURE:- 1. Connection are made as per circuit diagram. 2. Note down the resistance in each phase using multimeter 3. Switch On AC power supply 4. Then the speed of motor is taken for each resistance per phase 5. The graph was drawn between resistance v/s speed

OBSERVATION TABLE:- S.N. Speed in rpm Resistance in m 1. 2. 3. 4. 5. GRAPH:-

PRECAUTION:- 1. The potential barrier should be in maximum position. 2. The motor should be started without load 3. Initially TPST switch is in open position.

RESULT:-Thus the speed test of three phase slip ring induction motor was performed and the c/s curve drawn.

VIVA QUESTION

1. The principle of operation of induction motor is similar to ANS- Transformer 2. The relative speed b/w rotor and stator flux is ANS-Zero 3. Under operating condition rotor circuit of I.M. ANS-Always closed 4. If the rotor circuit is open ANS- Motor not run 5. If two leads from slip ring are interchanged then motor ANS-Continue running in same direction as before 6. How the direction of rotation is reversed ANS-Transposing any two leads from supply 7. Define synchronous speed ANS-Speed at which the stator magnetic field rotates 8. Slip at the time of starting of I.M. ANS- 1 9. Slip is negative how ANS-Rotor rotates at a speed more than synchronous speed and in the direction of rotation of stator field 10. The frequency of rotor current at stand still ANS- f

EXPERIMENT NO:07 No load test on 3- Induction motor AIM:-To conduct the no load test on 3- Induction motor to obtain the equivalent circuit of 3- squirrel cage Induction motor NAME PLATE DETAILS:- Type of I.M. Squirrel cage Voltage 415V Current 4.7A Speed 1400rpm APPARATUS REQUIRED:-

S.N Apparatus Type

Range Quantity

1. Ammeter M.I. 0-5A 1 2. voltmeter M.I. 0-600V 1 3. Wattmeter UPF 600v ,5A 2 4. Connecting

wire As per

required THEORY:-A 3 phase induction motor consist of stator, rotor and other associated parts. In the stator there is a 3 phase winding magnetic field. A magnetic flux is generated in rotor due to the Induction effect, produced due to the relative speed between rotor winding and relative flux. CIRCUIT DIAGRAM:-

PROCEDURE:- 1. Connection are given as per circuit diagram 2. Auto transformer is varied to have relative voltage applied 3. The meter reading on the tabulation.

FORMLA:- Wsc = (3)1/3 VoIoCOS W Iw = IoCOS Amp Voc = open circuit voltage Ioc = Open circuit current Ro = (vo/Iw) , Xo = (vo/Iy) CALCULATION:- OBSERVATION TABLE:- S.N. Voltage Voc Current Ioc Wattmeter reading W1 W2 PRECAUTION:-

1. The Auto transformer must kept at minimum potential position position. 2. The motor should be started without load 3. Initially TPST switch is in open position.

RESULT:- Thus the no load test on 3- Induction motor are performed and the equivalent circuit parameter are calculated.

VIVA QUESTION 1. What is the relative speed between stator MMF and the rotor MMF ANS- Zero 2. What is the speed of MMF produced by the 3 phase current

ANS- Stand still with respect to stator MMF 3. In slip ring I.M. the frequency of rotor currents can be measured by ANS- DC moving coil Millivoltmeter 4. In I.M. the value of phase reactance in comparison to phase resistance ANS- Quite high 5. The direction of rotor current produced in induction motor can be determined by ANS- Flemings RHR 6. In case of I.M. leakage flux is more compare with transformer why

ANS- Air gap between rotor and stator

EXPERIMENT NO:08 Blocked rotor test on 3- Induction motor AIM:- To conduct the block rotor test on 3- Induction motor and to draw the equivalent circuit of 3- squirrel cage Induction motor. NAME PLATE DETAILS:- Type of I.M. Squirrel cage Voltage 415V Current 4.7A Speed 1400rpm APPARATUS REQUIRED:-

S.N Apparatus Type Range Quantity 1. Ammeter M.I. 0-5A 1 2. voltmeter M.I. 0-600V 1 3. Wattmeter UPF 600v ,5A 2 4. Connecting

wire As per

required THEORY:- The three phase induction motor consist of stator and rotor with the other associated parts in the stator. The three phase winding is provided. The winding of three phase is displayed in phase by 1200 A three phase squirrel cage is fed to the three phase winding , these winding produced a resultant magnetic flux and it rotate in phase like a solid magnetic pulse being rotate magnetically. BLOCKED ROTOR TEST:-

1. Initially the TPST switch is kept open 2. Auto Transformer must be kept to minimum potential position 3. The machine should be started on full load

CIRCUIT DIAGRAM:-

PROCEDURE:- 1. Connection are given as per circuit diagram 2. Motor is started on full load or blocked rotor test. 3. Auto transformer is varied to have rated current flowing in motor FORMULA:- Wsc = 3.12Ro Watt R0 = Wsc/3 (Isc)2 Zo1 = Vsc/Isc Xo1 = (Zo12 Ro12)1/2 CALCULATION:- OBSERVATION:-

S.N. Voltage Voc Current Ioc Wattmeter reading W1 W2

PRECAUTION:-

1. Connection are given as per circuit diagram 2. Auto transformer is varied to have relative voltage applied 3. The meter reading on the tabulation.

RESULT:-

Thus the blocked rotor test on 3- Induction motor is performed. VIVA QUESTION

1. Rotor input of three phase induction motor is equal to ANS-Input to motor stator copper loss and iron loss 2. What is the ratio of rotor copper loss and rotor input ANS- S(slip) 3. Synchronous watt is ANS-the torque which under synchronous speed would develop a power of 1 Watt or power input to rotor in watt 4. The power factor of I.M. at no load is around ANS- 0.2 lagg 5. Power factor at full load is ANS- 0.85 lagg 6. Blocked rotor test of I.M. corresponds in case of transformer is ANS- Short-circuit operation 7. Short circuit test is performed on an induction motor to determine ANS-Short circuit current, equivalent resistance , power factor 8. Circle diagram is employed to determine the ANS-Induction motor 9. An induction motor is said to be crawling when ANS-It run at one-seven of rated speed 10. Zero sequence impedance of a three phase squirrel cage I.M. is due to ANS- stator circuit third space harmonics

EXPERIMENT NO:09 Synchronization of alternator by dark lamp method

AIM:- To synchronize the given 3- alternator with bus bar NAME PLATE DETAILS:- Voltage 415V Current 3.5A Speed 1500rpm Power 3Hp APPARATUS REQUIRED:-

S.N Apparatus Type Range Quantity 1. Ammeter M.I. 0-5A 1 2. voltmeter M.I. 0-600V 1 3. Connecting

wire And lamp As per

required THEORY:-The synchronous generator (FIG.1) can be connected to the bus bars (represented by an equivalent generator) only when each of the voltages between R1 and R2,between Y1 and Y2, and between B1 and B2 is zero at every instant of time. This condition is fulfilled when the line voltages on the generator side are equal, at all instants of time, to the corresponding voltages on the bus bar side. This is possible only if the following conditions are fulfilled: a. The voltages Vg and Vb are equal in magnitude and are in phase. b. Their frequencies are the same. c. The generator and the bus bars have the same phase sequence. When these conditions are fulfilled, the synchronizing switch between the generator and the bus can be switched on

CIRCUIT DIAGRAM:- Synchronizing of alternator with bus bar

PROCEDURE:-

1. Make the connection as per circuit diagram 2. Synchronizing circuit should be kept open at starting 3. Alternator is run with the help of prime mover at the synchronizing speed. 4. The voltage of the alternator is made equal to bus bar voltage with the help of the field

regulation 5. If all the lamps are glowing and dimming simultaneously one after the other the phase

sequence is correct , if all the lamp is glowing and dimming at the same timing the phase sequence is wrong . In this case interchange the connection of any two phase on bus bar side or alternator side. Thus the phase sequence is correct.

6. If the lamp are glowing and dimming very slowly the frequency are same ,this condition is achieved by a adjusted the speed of the alternator by varying the field regulator of DC motor.

7. After all the condition satisfied close the synchronizing switch.

OBSERVATION TABLE:-

S.N. IL (Amp) VL (volt) V2 (Volt)

PRECAUTION:-

1. The potential barrier should be in maximum position. 2. The motor should be started without load 3. Initially TPST switch is in open position

APPLICATION:- This method is used in substation and industry for the synchronizing of incoming alternator.

RESULT:-

The synchronizing of three phase alternator by lamp method has been done

VIVA QUESTION

1. What is the purpose of this experiment ANS-Synchronizing the alternator 2. Number of slip ring in three phase alternator ANS-2 3. The MMF produced by single phase winding is ANS-Pulsating and stationary 4. Synchronous motor generally are ANS-Salient pole rotor 5. In three phase synchronous motor the magnitude of field flux is ANS-Remain constant at all loads 6. As the load is increased the motor speed is ANS- remain constant 7. Synchronizing power comes from ANS-If Rotor speed either exceeds or fall below the synchronous speed 8. The value of load angle for a synchronous motor depends mainly upon ANS-load

EXPERIMENT NO:10

To study of synchronous induction motor AIM:- To study the construction , working principle and performance c/s of synchronous induction motor. NAME PLATE DETAILS:- Type Voltage Current Power Speed APPARATUS REQUIRED:- S.N. Apparatus Type Quantity 1. 3 Phase Synchronous Induction Motor AC 1 2. Auto Induction Starter panel AC 1 3. TPDT knife switc 1 4. Tachometer Digital 1 THEORY:- In the applications where high starting torque and constant speed are desired then synchronous induction motor can be used. It has the advantages of both synchronous motor and induction motor. The synchronous motor gives constant speed whereas induction motors can be started against full load torque. Consider a normal slip ring induction motor having three phase winding on the rotor as shown in the figure. The motor is connected to the exciter which gives DC supply to the rotor through slip rings. One phase carries full d.c. current while the other two carries half the full DC current as they are connected in parallel. Due to this DC excitation, permanent poles (N and S) formed on the rotor. Initially it is run as a slip ring induction motor with the help of starting resistances. When the resistances are cut out the motor runs with a slip. Now the connections are changed and the exciter is connected in series with the rotor windings which will remain in the circuit permanently. As the motor is running as induction motor initially high starting torque (up to twice full load value) can be developed. When the DC excitation is provided it is pulled into synchronism and starts running at constant speed. Thus synchronous induction motor provides constant speed, large starting torque, low starting current and power factor correction PROCEDURE:-

1. Note down the name plate details of the motor 2. Connections are given as per the circuit diagram. 3. Close the TPST switch in order to supply the rated voltage to the motor. 4. Start the motor by closing the TPDT switch (position 123) with the rotor resistance

starter in maximum resistance position to run the motor at rated speed. 5. Change the position of TPDT Switch (position 123) in order to excite the rotor by DC source where the excitation should be given gradually through the potential divider to maintain the synchronous speed. 6. The resistance if the stator can be measured using Dc supply with voltmeter and ammeter or directly using multimeter.

APPLICATION:- Synchronous Induction motor are used where a high starting torque are required.

PRECAUTION:-

1. The motor should be started without load. 2. The rotor resistance starter should be kept in the maximum resistance position while

starting. 3. The field potential divider should be kept in the maximum resistance

RESULT:- The study of synchronous induction motor done successfully. VIVA QUESTION

1. In salient pole rotor how many poles ANS- two or four 2. In turbo alternator rotor is made of ANS- Forged steel 3. In modern alternator rotating part is ANS- Field system 4. Which of the alternator is used in hydroelectric power station ANS- Salient pole alternator 5. Concentrated winding has ANS- One coil per pair of pole per phase 6. Skew of rotor bar eliminates ANs- The effect of space harmonics 7. Distributed winding is preferred over concentrated winding ANS- Improves the generated EMF waveform 8. Harmonics in the EMF generated in an alternator can be reduced by ANS- Skew the slots 9. Armature winding in synchronous machine ANS- May be either closed one giving delta connection or open one giving star connection. 10. In alternator short circuit current can be limited by ANS- Unsaturated synchronous impedance.