WorksheetsInduction motors week 14
Total questions: 15
Worksheet time: 1hrs 20mins
It is advisable to avoid line starting of induction motor and uses starter because
Starting torque is very high
It will pick up very high speed
Motor takes 6 to 7 times its full load current
It will run in inverse direction
A change of 5% in the supply voltage of a 3 phase induction motor will produce its torque a change of approximately
7%
8%
9%
10%
A pump induction motor is switched on to supply 30% lower than its rated voltage. The pump runs. What will eventually happen?
Get heated and consequently get damaged
Start after sometime
Continue to run at low speed without damage
Nothing will happen
If the air gap of an induction motor is increased
None of these
The magnetizing current will increase
All of these
The magnetizing current will decrease
In an induction motor the torque is related with the supply voltage as
T is proportional to V^ (1/2)
T is proportional to V
T is proportional to V^2
T is for teen titans
In a double squirrel cage induction motor, the outer cage winding has
High resistance
Low resistance
High reactance
Low reactance
If the rotor slots are made deeper, the rotor resistance is
increased under running condition
decreased under running condition
decreased at starting
increased at starting
In a squirrel cage induction motor, the number of rotor bars is generally
Prime number
Odd number
Even number
None
For the same kVA rating, the leakage flux in induction motor is ____ that of transformer.
None
About the same
More than
Less than
The stator and rotor cores of an induction motor are made up of laminated sheets
to reduce the hysteresis loss in the core
to enable the stator and rotor cores dissipate heat more effectively
to reduce the eddy-current loss in the core
to make the rotor and stator mechanically strong
A single phase induction motor is rated 5 hp, 75% power factor and 220 volts. What is its full load current?
(a)
A 5 hp, 3-phase motor draws current when connected to 230 V. Determine the current drawn by the motor if the power factor is 0.90 and efficiency of 83%.
(a)
A 3-phase motor is rated 750 hp at 460 volts line to line, 0.85 pf lagging and 0.95 efficiency. Solve for the rated current.
(a)
The losses in a 220-V, three-phase, 25 Hz, 4- pole induction motor at full-load are as follows: Core = 3.0% Friction and windage = 2.0% Stator Cu loss = 4.0% Rotor Cu loss = 2.0% At 70% of full-load of the machine, determine its efficiency.
(a)
A 10-hp, 4-pole, 25-Hz, 3-φ induction motor is taking 9,100 watts from the line. The core loss is 290 watts; stator copper loss is 568 watts; rotor copper loss is 445 watts; and the friction and windage loss is 121 watts. Determine the output torque in Newton-meter.
(a)
