2. Determine developed torque and shaft torque of 220-V, 4-pole series motor with 800 conductors wave-connected supplying a load of 8.2kW by taking 45A from the mains. The flux per pole is 25 mWb and its armature circuit resistance is 0.60. Ans.[143.25 Nm, 135.25 Nm]

6- In a stepper motor, how is the speed of rotation determined? a) By the current supplied to the motor. b) By the magnitude of the voltage applied. c) By the load applied to the motor. d) By the frequency of the waveforms used. 7- A transformer core is laminated to a) reduce hysteresis loss b) reduce eddy current losses c) reduce copper losses d) reduce all above losses 8- An induction motor with 580 r.p.m. speed at 60 Hz will have a) 8 poles b) 6 poles c) 4 poles d) 2 poles 9- If any two phases for an induction motor are interchanged a) the motor will run in reverse direction b) the motor will run at reduced speed c) the motor will not run d) the motor will burn 10- No-Load speed of which of the following motor will be highest? a) Shunt motor b) Series motor c) Short-Shunt compound motor d) Long-Shunt compound motor

A three phase 6000 V alternator has the following O.C.C. at normal speed: Field current : 14 18 23 30 43 Terminal voltage: 4000 5000 6000 7000 8000 With armature short circuit and fall load current flowing the field current is 17 A And when the machine is suppling fall-load of 2000KVA at zero-power factor the field current is 42.5 A, and the terminal voltage is 6000 V. Determine the field current that required when the machine is supplying the fall-load current at 0.7 p.f. lagging.

Find the value:

T-a. The direction of rotation of a single-phase split-phase motor can be change by........ a) reversing the connection of the start winding b) reversing the connection of the run winding c) reversing the connection of the start and run winding at the same time d) "a" or "b", not "c" T-b. Single-phase split-phase motors using an electrolytic capacitor in the start winding circuit should not be cycled more than about__________ time per hour. a) 8 b) 12 c) 24 d) none of the above T-c. When replacing the capacitor in a capacitor-start induction-run motor, one must be sure to replace the bad capacitor with__________ . a) a smaller one b) one of the same size c) a larger one d) none of the above

Two identical 2,000 kW alternator operates in parallel. The governor of the first machine is such that the frequency drops uniformly from 50 Hz at no-load to 48 Hz at full-load. The corresponding uniform speed drop of the second machine is 50 Hz to 47.5 Hz. What is the maximum load that can be delivered without overloading either machine?

A four – pole dc generator armature is lap wound with 60coils. Each coil has 8 turns. Determine the flux/pole required to generate 200V at 1500 rev/min.

Name three factors that determine the torque produced by an induction motor.

A PWM signal is sent to a permanent magnet DC motor through an H-bridge circuit. The PWM frequency is 100 kHz, the DC voltage source is 16 volts, and the specification of the motor is given as: voltage = 16 volts, no load speed = 1500 RPM, holding torque = 2 Nm. a. Draw the voltage signal delivered to the motor when the duty cycle is 20% and 80% (at least draw for 5 periods). Calculate the speed of DC motor when the duty cycle is 20% and 80%. b. C. Estimate the output power when the duty cycle is 20% and 80%. Assume that the motor efficiency is 100%.

Two shunt generators A and B operates in parallel and their load characteristicsmay be taken us straight lines. The voltage of the generator A falls from 240 V atno-load to 220 V at 200 A while that of B falls from 245 V at no load to 220 V at150 A. Determine the current which each machine supplies to a common load of300 A and the bus-bar voltage at this load.