WorksheetsAC DRIVES
Total questions: 14
Worksheet time: 11mins
The starting torque of an indication motor is maximum when
Rotor resistance equals rotor reactance
Rotor resistance is twice the rotor reactance
Rotor resistance is half the rotor reactance
Rotor resistance is R2 times the rotor reactance
The emf induced in the rotor of an induction motor is proportional to
Voltage applied to stator
Relative velocity between flux and rotor conductors
Both (a) and (b) above
Slip
The field winding of a three phase synchronous machine is excited by
Single-phase ac supply
Three- phase ac supply
Dc supply
Supply obtained from an inverter
This starting method typically allows a motor to develop 150% of its rated ________ while the VFD is drawing less than 50% of its rated current from the mains in the low speed
Torque
Energy
Force
Angular momentum
Main advantage of an ac motor as compared to a DC motor is
Large slip
lower starting torque
Higher efficiency
Higher power factor
The starting torque of a squirrel-cage induction motor is
Full-load torque
Slightly more than full-load torque
Low
Negligible
A 50 Hz, 3-phase induction motor has a full load speed of 1440 r.p.m. The number of poles in the motor is
2 pole
4 pole
6 pole
8 pole
Which of the following motor has high starting torque?
Slip ring Induction motor
Squirrel cage Induction motor
No load test of 3-phase induction motor used to determine
Variable loss
Constant loss
Eddy current loss only
Hysteresis loss only
Introducing the external resistance increases
(i) speed (ii) output power (iii) starting torque
(iii)
(ii),(iii)
(ii)
(i), (ii), (iii)
At what range the PLL can maintain the lock in the circuit?
Lock in range
Input range
Feedback loop range
What is the function of low pass filter in phase-locked loop?
Improves low frequency noise
Removes high frequency noise
Tracks the voltage changes
Changes the input frequency
The PLL device is:
Feedback system that compares output frequency and input frequency
Feedback system that compares output phase and input phase
Linear system that compares output resistance and input resistance
Non Linear system that compares output current and input current
The PWM control of DC motor varies
exponentially with speed
linearly with speed
inversely with speed
parabolically with speed
