81

Describe any two features of the Double cage
induction motor.


Features of Double cage induction motor

82

Describe the conditions to be necessary for the cascade
operation of the three phase induction motor.


Cascade operation of three phase
induction motor

83

Which type of cascade connection of the induction
motor should provide very low or zero torque?


Differential connection

84

What should be the frequency of the rotor induced emf
in the injected emf speed control method of induction motor?


The frequency of the injected emf should be same as the slip frequency
( rotor frequency ).

85

What are the advantages of the Kramer speed control
of the induction motor?


Advantages of Kramer speed control

86

Which parameter the locus of the circle diagram
represents?


Rotor current as refer to stator side

87

Describe the method to find out no load parameter G_{0}
and B_{0} of the three phase induction motor.


No load parameters
I_{0} = VY_{0}
And W_{0} =
3G_{0}V^{2}
G_{0} = W_{0}
/ 3V^{2}
And B_{0} = √
(Y_{0}^{2} – G_{0}^{2})

88

Give the reason : The one wattmeter shows negative
reading in the no load test of the three phase induction motor.


Induction motor at no load
W_{1} α Cos (
30 + Ф )
W_{2} α Cos (
30 – Ф )
Where Ф is the load
power factor

89

Which parameters can find out by performing blocked
rotor test in the three phase induction motor?


Short circuit current at normal voltage
Power factor Cos Ф_{sc} at short circuit
Total winding impedance Z_{01}, reactance X_{01} and
resistance R_{01} as referred to the stator side

90

Describe the effect on torque and starting current
if the supply voltage is reduced by 50% in the three phase induction motor?


Effect of supply voltage

91

Is there any effect on power factor by using primary
resistor starter in the three phase induction motor?


The power factor improves slightly due to resistors connected to the
line.

92

Describe the effect of speed on the rotor induced
emf.


Effect of speed on rotor induced emf

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