1. Which duty cycle has on load and off-loads period?
A. Intermittent duty
B. Short-time duty
C. Continuous duty with constant load
D. Continuous duty with variable load
Answer: A
The intermittent duty cycle has frequent on-load and off-loads periods. The on-load period and off-loads periods are too short to achieve steady-state thermal condition.
2. Which motor is preferred for Jaw crushers?
A. WRIM
B. SCIM
C. Belt slip ring IM
D. DC shunt motor
Answer: C
Belt slip ring IM is preferred for the operation of Jaw crushers. A high starting is provided by the Belt ring IM. Slip rings are used to add external resistance.
3. A high starting torque is offered by the Belt Conveyors.
A. True
B. False
Answer: A
The Belt Conveyors can provide continuous-flow transportation. The amount of material transported on a conveyor system depends upon belt speed, and belt width.
4. Which starting method is the worst method in Induction motor?
A. Direct online starting
B. Autotransformer starting
C. Reactance starting
D. Star-Delta starting
Answer: C
The Reactance starting method is the worst method in an Induction motor. It uses the concept of the potential divider. The losses are very high in the case of the Reactance starting method.
5. Induction motor is also known as __________
A. Frequency changer
B. Frequency remover
C. Time period remover
D. DC machine
Answer: A
The Induction motor is also known as a frequency changer. The stator frequency can be changed using the slip concept. The rotor frequency of IM is slip×(stator frequency).
6. The capacity of the Crane is expressed in terms of tonnes.
A. True
B. False
Answer: A
Cranes are used to carry or lift heavy loads. The capacity of a Crane is expressed in terms of tonnes. 1 tonne is equal to 1000 Kg.
7. 1800 second-rated motors are used for __________
A. Heavy-duty cranes
B. Light duty cranes
C. Medium duty cranes
D. Intermittent duty cranes
Answer: C
Medium duty crane motor is used to develop high starting torque. They provide the output for a specified interval of time without exceeding a specified temperature.
8. Calculate the frequency of the rotor side of the IM if the value of slip is 0.34 and the supply frequency is 70 Hz.
A. 23.8 Hz
B. 22.7 Hz
C. 24.5 Hz
D. 23.1 Hz
Answer: A
The frequency of the rotor side is low as compared to the supply frequency.
The rotor frequency is slip×(supply frequency)
=.34×70=23.8 Hz.
9. Calculate the frequency of the stator side of the IM if the value of slip is 0.04 and rotor frequency is 2 Hz.
A. 50 Hz
B. 49 Hz
C. 45 Hz
D. 51 Hz
Answer: A
The frequency of the stator side is high as compared to the rotor side. The stator frequency is (rotor frequency) ÷ slip
= 2÷.04 = 50 Hz.
10. Calculate the resonant frequency if the values of the capacitor and inductor are 4 F and 4 H.
A. .25 rad/sec
B. .26 rad/sec
C. .28 rad/sec
D. .29 rad/sec
Answer: A
During resonance condition XL=Xc. The value of the resonant frequency is
1÷√LC=1÷√16=.25 rad/sec.
The voltage across the capacitor and inductor becomes equal.
