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WorksheetsAC Motor Drives_2
Total questions: 19
Worksheet time: 10mins
Main advantage of an ac motor as compared to a DC motor is
less maintenance
expensive
can work in any environment
controllability
Which of the following is the advantage of double squirrel cage rotor as compared to the round bar cage rotor?
Large slip
Lower starting torque
Higher efficiency
Higher power factor
The advantages of a group driver electric drive are
High efficiency
Low Noise
Constant speed
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)
The maximum EMF is induced in the rotor of a 3-phase induction motor when it
No-load
Full-load
Half-load
rotor is blocked
Which type of braking can be used for saving energy?
dynamic
plugging
regenerative
The concept of V/f control of inverters driving induction motors resuls in
constant torque operation
speed reversal reduced
magnetic loss
hormonic elimination
Torque slip chara of an AC motor is as follows
The slip recovery scheme is a part of the synchronous speed changing technique.
TRUE
FALSE
The concept of V/f control of inverters driving induction motors resuls in
constant torque operation
speed reversal
Reduced magnetic loss
hormonic elimination
Which type of braking can be used for saving energy?
dynamic
plugging
regenerative
If the stator voltage and frequency of an induction motor are reduced proportionately, its
Locked rotor current is reduced
Torque developed is increased
Magnetizing current is decreased
Both (a) and (b)
The disadvantages of scherbius system used for speed controlling in 3 phase induction motor is
It cannot be used for slip ring induction motors
It cannot be used for squirrel cage induction motors
It can be used for large induction motors
Introducing the external resistance decreases
(i) speed (ii) output power (iii) starting torque
(iii)
(ii),(iii)
(i),(ii)
(i), (ii), (iii)
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
