Which of the following statements regarding hysteresis motor is in incorrect ?

If the area of hysteresis loop of a material is large, the hysteresis loss in this material will be

A

Zero

B

Small

C

Large

D

None of the above

A centrifugal pump which circulates a hot liquid metal at 500 degree Celsius is driven by a 3600 rpm electric motor. The motor is coupled to the pump impeller by a horizontal steel shaft of dia 25 mm. Let us assume the motor temperature as 60 degree Celsius with the ambient air at 25 degree Celsius, what length of shaft should be specified between the motor and the pump? It may be presumed that the thermal conductivity of the shaft material is 35W/m K and that the convective film coefficient between the steel shaft and the ambient air is 15.7W/square m K

A

38.96 cm

B

54.76 cm

C

23.76 cm

D

87.43 cm

A hysteresis motor works on the principle of

A

hysteresis loss

B

magnetisation of rotor

C

eddy current loss

D

electromagnetic induction

In a hysteresis motor, the rotor must have

A

retentivity

B

resistivity

C

susceptibility

D

none of the above

The direction of rotation of an hysteresis motor is determined by

A

interchanging the supply leads

B

position of shaded pole with respect to main pole

C

retentivity of the rotor material

D

none of these

Hysteresis motor is particularly useful for high-quality record players and tape-recorders because

A

it revolves synchronously

B

it is not subject to any magnetic or mechanical vibrations

C

it can be easily manufactured in extremely small sizes of up to 1 W output

D

it develops hysteresis torque which is extremely steady both in amplitude and phase

The rotor of a hysteresis motor is made of

A

aluminium

B

cast iron

C

chrome steel

D

copper

Which of the following statements regarding two value capacitor motor is incorrect ?

A

It is a reversing motor

B

It is preferred to permanent-split single-value capacitor motor where frequent reversals are required

C

It has low starting as well as rushing currents

D

It has high starting torque

Which of the following statements regarding reluctance-start motor is incorrect ?

A

It is similar to reluctance motor

B

It is basically an induction motor and not a synchronous one

C

So far as its basic working principle is concerned, it is similar to shaded pole motor

D

the air-gap between rotor and salient poles is non- uniform

Which of the following statements regarding a reluctance motor is incorrect ?

A

It cannot be reversed, ordinarily

B

It requires no D.C. field excitation for its operation

C

It is nothing else but a single-phase, salient pole synchronous-induction motor

D

Its squirrel cage-rotor is of unsym-metrical magnetic construction in order to vary reluc-tance path between stator and rotor

Which of the following statements regarding hysteresis motor is in incorrect ?

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