Induction Machines

Induction Machines

1.Speed of the stator field of an Induction motor is

(a) Synchronous speed
(b) Any speed
(c) Less than Synchronous
(d) Slip Speed
Ans(a) Synchronous speed

2.Difference in speed between stator field and rotor
(a) Full load speed
(b)No load speed
(c)Slip
(d) Regulation
Ans:(c)Slip

3.Frequency of current in rotor

(a)Supply frequency
(b)Less than supply frequency
(c)Greater than supply frequency
(d)Slip frequency

Ans;(d) Slip Frequency

4. Shape of the torque slip curve is
(a) Rectangular Hyperbola
(b)Parabola
(c)Sine
(d) Cosine
Ans;(a) Rectangular Hyperbola

5.Machine with negative slip
(a)Induction Motor
(b) Brake
(c)Induction Generator
(d)Synchronous machine
Ans(c) Induction Generator



6.When rotor is at standstill
(a)slip is zero
(b)slip is one
(c)Any slip
(d)Slip is infinity
Ans;(b)Slip is one

7.When the motor runs at synchronous speed slip is
(a) One
(b) Infinity
(c)Zero
(d)Two
Ans:(c)Zero

8.Which torque is greater
(a)Break down
(b)Full load
(c) No load
(d) Running
Ans:(a) Break down

9.An Induction motor is analogous to
(a)DC motor
(b)Transformer
(c)Synchronous motor
(d) DC Generator
Ans:(b)Transformer

10.Blocked rotor test is analogous to
(a) SC test
(b)OC test
(c)Swinburnes
(d) Load test
Ans:(a)SC test

11.No load test is analogous to
(a) SC test
(b) Load test
(c)OC test
(d)Swinburnes test
Ans:(c)OC test

12.Rotor Copper loss is equal to
(a)Friction loss
(b)Stator loss
(c)slip times rotor input
(d)rotational loss
Ans: (c)slip times rotor input

13.For the purpose of plugging
(a)N is positive w.r.t to Ns
(b)N is zero
(c)N is infinity
(d)N is negative w.r.t to Ns
Ans: (d)N is negative w.r.t to Ns

14.Parameter from no load test is
(a)Ri and Xi
(b)Ro and Xo
(c) Copper loss
(d)Impedance
Ans:(b)Ro and Xo


15.If stator field is rotating in clockwise direction rotor rotates in
(a) Any direction
(b)Cannot predict
(c)Anticlockwise
(d) clockwise
Ans: (d)clockwise

16.Blocked rotor test is conducted at
(a)High voltage
(b)Rated current
(c)High current
(d)Rated voltage
Ans(b)Rated current

17.Speed of rotor field in space
(a)N
(b)Any speed
(c)Ns
(d)Slip speed
Ans(c)Ns

18.Line joining tangent and output line in a circle diagram gives
(a)Cu loss
(b)Stator loss
(c)Maximum output
(d)Maximum Torque
Ans;(c)maximum Output


19..Line joining tangent and Torque line in a circle diagram gives
(a)Cu loss
(b)Stator loss
(c)Maximum output
(d)Maximum Torque
Ans;(d)maximum Torque


20.No load test is conducted at


(a)High voltage
(b)Rated current
(c)High current
(d)Rated voltage
Ans: (d)Rated voltage