Industrial Drivers

21. Heat control switches are used in

1. transformers
2. cooling ranges
3. three phase induction motors
4. single phase

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22. Heavy duty cranes are used in

1. ore handling plants
2. steel plants
3. heavy engineering workshops
4. all of the above

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23. hich of the following motors always starts on load?

1. Conveyor motor
2. Floor mill motor
3. Fan motor
4. All of the above

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24. In _________ method of staging three phase induction motors the starting voltage is not reduced.

1. auto-transformer
2. star-delta
3. slip ring
4. any of the above

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25. In _________ the speed can be varied by changing the position of brushes.

1. slip ring motor
2. schrage motor
3. induction motor
4. repulsion motor

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26. In a paper mill where constant speed is required

1. synchronous motors are preferred
2. A.C. motors are preferred
3. individual drive is preferred
4. group drive is preferred

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27. In case of _________ speed control by injecting e.m.f. in the rotor circuit is possible,

1. d.c. shunt motor
2. schrage motor
3. synchronous motor
4. slip ring induction motor

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28. In jaw crushers a motor has to often start against _________ load.

1. heavy
2. medium
3. normal
4. low

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29. In series motor which of the following methods can be used for changing the flux per pole?

1. Tapped field control
2. Diverter field control
3. Series-parallel control
4. Any of the above

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30. In squirrel cage induction motors which of the following methods of starting cannot be used?

1. Resistance in rotor circuit
2. Resistance in stator circuit
3. Auto-transformer starting
4. Star-delta starting

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