Part A: True False (10* I-10) l. Armature AC resistance is 1.5 times greater tha
ID: 2266814 • Letter: P
Question
Part A: True False (10* I-10) l. Armature AC resistance is 1.5 times greater than armature DC resistance of synchronous machine. 2. In this LAB, we used motor to provide mechanical power to generator? 3. Variable three phase supply was used in the experiment of three phase induction motor 4. 'Brake' button of control unit was used to control the torque applied to generator 5. For a three phase system with neutral (3 phase 4 wire) we need 3 fuses? 6. Tachometer measures the speed of machine. 7. Generated voltage (Eo) vs field current (le) represents the SCC curve of DC generator 8. Short circuit current over open circuit voltage per phase is the synchronous impedance 9. You will choose rms for AC and average for DC quantity. 10. Short circuit test and open circuit test are performed on rated current and voltage respectively Part B: Writing Answers 11. Level/identify UA1, UB1, UA2, UB2 in the following diagram (02) Profi Cassy Sensor Cassy 12. Write down the equation of voltage regulation (VR) for a transformer. Three transformers each are having VR of 5%, 7% and 10%, which one would you prefer for your work and why? (02)Explanation / Answer
1.Due to Skin effect the AC resistance is 1.5 times than that of DC resistance. Hence it is true.
2. For mechacial support we will connect the motor shaft with the generator shaft. Hence it is true.
3.In the experiment of 3 phase induction motor fixed 3 phase supply is used not variable supply.So the given statement is False.
4.Brake button is used to control the applied Torque to generator.Hence it is true.
5.For 3 phase 4 wire system we will use 3 fuses for 3 phases only .There is no fuse for nuetral wire.Hence given statement is True.
6.tachometer is used to measure the Speed of the motor.hence it is true.
7. Generator voltage and file current represents the open circuit characteristics(OCC) of the DC generator.hence given statement is False.
8.synchronous impedance is the ratio of the open circuit voltage to short circuit current.Here given statement is in opposite to the defination.So it is False.
9.For AC we will use rms as indiaction .In DC we will use average as indication because of frequency effect.Hence it is true statemet.
10.Short ciruited test conducted with rated current and reduced voltage
whereas open circuit test is conducted with rated voltage and reduced current.
Hence given statement is true