ELECTRIC MACHINES LAB QUESTIONS

1.Conduct a suitable experiment to obtain the magnetization characteristics at 1200 rpm and find the critical speed of the given DC machine which delivers electrical power, has a parallel field winding and capable of building its own field. Also verify whether the machine is able to build up the voltage below the critical speed.(Self-excited DC generator)

2. Conduct a suitable experiment on the given DC machine which has a parallel field winding, delivers electrical power and is excited by a DC source. Plot the terminal characteristics of the machine.(Separately excited)

3. Identity the different ways of connecting the two field windings of a DC machine which is based on the principle that when a conductor is rotated in a magnetic field, a voltage will be generated in the conductor. Plot the voltage –current characteristics of DC machine when the flux produced by both the field winding aid each other.(Compound generator-cumulative)

4. Plot the performance at 30%, 50%, 80% and 100% of full load on the given machine DC machine which converts electrical energy into mechanical energy. The DC machine has both shunt field and series field winding.(Load test on compound motor)

5. Plot the speed-torque characteristics of the DC machine which is used for constant speed applications like lathes, centrifugal pumps and blowers.(Load test on shunt motor)

6. Conduct a suitable experiment to determine the efficiency and to obtain the performance characteristics at 30%, 60%, 90% and 100% of full load on the given DC machine with a series field winding and very high starting torque.(Load test on DC series motor)

7. By indirect testing of the given DC machine predetermine the efficiency of the machine when it works as motor and plot the efficiency curve. Also plot the efficiency curve of the given DC machine when it works as generator for 20%, 40%, 60%, 80%, 100% and 120% of the full load.(Swinburne’s)

8. For a specific application in a paper manufacturing unit it is required to run a DC shunt motor below the rated speed and also above the rated speed. Is it possible to do speed control above as below the rate speed on the Dc shunt motor? If it is possible then experimentally prove and plot the characteristics.(Speed control on Dc shunt motor)

9. Predetermine the efficiency of the two identical shunt machines are coupled mechanically and also connected electrically in parallel. Plot the efficiency versus load power characteristics of both the machines.(Hopkinson’s)

10. Conduct a load test on the given static machines which consists of two electric circuits interlinked by a common magnetic circuit and plot the efficiency versus load power characteristics.(Load test on single phase transformer)

11. Conduct a load test on the given static three phase machine which works under the principle of mutual induction and plot the efficiency versus load power characteristics.(3 phase transformer)

12. By conducting suitable test on the given single phase static machine draw its equivalent circuit referred to the supply side.(Load test and short circuit)

13. Predetermine the efficiency of the machine transfers energy from one circuit to another without a change in frequency. Plot the efficiency and regulation characteristics.(Open circuit and short circuit test for single phase transformer)

14.  Conduct a back to back test on a two identical static machines and plot the regulation and efficiency characteristics.(Sumpners)

15. Conduct a suitable experiment to measure the iron losses in the static electric machine and separate it into hysteresis and eddy current loss by using variable frequency approach.(Separation of losses in single phase transformer)

16. By conducting a direct load test on the given single phase static machine determine the efficiency of the machine under different load conditions. Plot the efficiency versus load power characteristics.(Load test one single phase transformer)

17. Conduct a suitable experiment to predetermine the secondary terminal voltage under full load and half load conditions and also determine the constants of the equivalent circuit by conducting a suitable experiment. The power factor of the load may be assumed to be 0.95 leading.(No load and short circuit test)

18. Identify the different ways of connecting the two field windings of a DC machine which is based on the principle that when a conductor is rotated in a magnetic field, a voltage will be generated in the conductor. Plot the voltage-current characteristics of DC machine when the flux produced by both the field windings opposes each other.(Compound generator –differential)

19. Conduct a suitable experiment to obtain the magnetization characteristics at 1200rpm and find the critical speed of the given DC machine which delivers electrical power, has a parallel field winding and excited by a separate source.(Separately excited)

20. Conduct suitable experiment to predetermine the efficiency characteristics of the DC machine when working as a generator and motor excluding the stary losses.(Swinburne’s)

1.       Conduct the following experiments on DC generator in which the field and armature windings are connected in parallel and it has own residual magnetism for its normal operation with neat graph and explanation.

i)                    Open circuit characteristics

ii)                   Load characteristics

(self-excited)

2.       Conduct the following experiments on DC generator in which the field and armature windings are connected in parallel and requires external excitation for its normal operation with neat graph and explanation

iii)                 Open circuit characteristics

iv)                 Load characteristics

(separately excited)

3.       Conduct suitable experiment on DC compound generator to draw the load characteristics for differential and cumulative connection. Explain the effect of the connections from the graph on motor.

4.       Conduct suitable experiment on DC compound generator for differential and cumulative connection and draw the graph between load current and voltage. Explain the effect  of the connections from the graph on motor.

5.       Conduct suitable experiment on DC shunt motor to draw the following performance characteristics at 50%, 75%, 100% and 120% of loading.

(a)    Output power Vs speed

(b)   Output power Vs efficiency

6.       Draw the following performance characteristics on Compound motor at 50%, 75%, 100% and 120% of loading by conducting suitable experiment.

(a)    Output power Vs load current

(b)   Output power Vs efficiency

7.       Conduct suitable experiment on DC series motor to draw the following performance characteristics at 50%,75%,100% and 120% of loading

(a)    Output power Vs speed

(b)   Ouput power Vs efficiency

8.       Draw the following performance characteristics on series motor at 50%, 75%,100% and 120% of loading by conducting suitable experiment .

(a) Output power Vs load current

(b)Ouput power Vs efficiency

9.       Predetermine the efficiency of an electrical motor by conducting suitable experiment and also draw its performance characteristics

(Swinburne’s)

10.   Conduct a suitable test on Dc shunt motor to control the speed below and above the rated speed to draw the performance characteristics. Explain these speed control methods with relevant equations.

11.   Conduct suitable test on motor-generator set to find the efficiency of the motor and generator. Derive the equations used. Also, write the merits and demerits of the particular method.

(Hopkinson’s)

12.   Conduct a regenerative test on which two identical DC shunt machines are coupled and calculate the efficiency of the machines. Derive the equations used and also write the merits and demerits of the method.

(Hopkinson’s)

13.   Draw the load characteristics of single phase transformer by conducting suitable experiment at 50%, 75%, 100% and 120% of loading and determine the efficiency of the transformer.

14.   What are the various three phase connections available? Conduct suitable experiment on three phase transformer and draw its performance characteristics.

15.   Conduct suitable experiment on single phase transformer to calculate the open circuit and short circuit parameters and also draw the equivalent circuit.

16.   Conduct suitable experiment on single phase transformer to find the core loss and iron loss. Also draw the equivalent circuit of the transformer.

(Separation of losses in single phase transformer)

17.   Explain the precautions and procedure for conducting sumpner’s test. Calculate core loss and iron loss of the transformer by conducting the test.

18.   Explain the precautions and procedure for conducting a test on two identical non rotating machines. Calculate efficiency of the transformer by conducting the test.

(sumpner’s test)

19.   Conduct suitable experiment on single phase transformer to calculate the no-load losses with suitable graph.

(Separation of no load losses)

20.   Conduct suitable experiment on single phase transformer to calculate the no-load losses with neat explanation.