# Design of Electrical Machines Questions and Answers – Parameters

This set of Design of Electrical Machines Multiple Choice Questions & Answers (MCQs) focuses on “Parameters”.

1. What is the formula for the resistance of running winding?
a) resistance of running winding = 0.021 * no of turns in running winding * length of mean turns of running winding * area of running winding conductor
b) resistance of running winding = 0.021 / no of turns in running winding * length of mean turns of running winding * area of running winding conductor
c) resistance of running winding = 0.021 * no of turns in running winding / length of mean turns of running winding * area of running winding conductor
d) resistance of running winding = 0.021 * no of turns in running winding * length of mean turns of running winding / area of running winding conductor

Explanation: First the no of turns in running winding along with length of mean turns of running winding and area of running winding conductor is calculated. On substitution the resistance of running winding is calculated.

2. How many parameters are present in the single phase induction motor?
a) 2
b) 3
c) 4
d) 5

Explanation: There are 3 parameters in the single phase induction motor. They are running winding resistance, rotor resistance and leakage reactance calculations of single phase motor.

3. How many parameters are present under the leakage reactance calculations?
a) 6
b) 5
c) 7
d) 4

Explanation: There are 7 parameters present under the leakage reactance calculations. They are slot leakage reactance, rotor slot leakage reactance, zigzag leakage reactance, overhang leakage reactance, skew leakage reactance, magnetizing reactance, total leakage reactance.

4. How is the winding arrangement and how is the conductors in each slot?
a) circular winding and same conductors in each slot
b) circular winding and different conductor in each slot
c) concentric winding and same conductor in each slot
d) concentric winding and different conductor in each slot

Explanation: The winding of the induction motors are concentric type. The different conductors are being used in each slot.

5. What is the relation of the total slot leakage reactance with number of stator slots?
a) slot leakage reactance is directly proportional to the number of stator slots
b) slot leakage reactance is indirectly proportional to the number of stator slots
c) slot leakage reactance is directly proportional to the square of the number of stator slots
d) slot leakage reactance is indirectly proportional to the square of the number of stator slots

Explanation: The slot leakage reactance is one of the parameters used in the leakage reactance calculations. The slot leakage reactance is indirectly proportional to the number of stator slots.
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6. What is the relation between slot leakage reactance and specific slot permeance?
a) slot leakage reactance is directly proportional to the specific slot permeance
b) slot leakage reactance is indirectly proportional to the specific slot permeance
c) slot leakage reactance is directly proportional to the square of the specific slot permeance
d) slot leakage reactance is indirectly proportional to the square of the specific slot permeance

Explanation: Specific slot permeance is one of the parameters present in the leakage reactance calculation. It is directly proportional to the slot leakage reactance.

7. What is the relation of the total slot leakage reactance with number of stator slots?
a) slot leakage reactance is directly proportional to the number of rotor slots
b) slot leakage reactance is indirectly proportional to the number of rotor slots
c) slot leakage reactance is directly proportional to the square of the number of rotor slots
d) slot leakage reactance is indirectly proportional to the square of the number of rotor slots

Explanation: The slot leakage reactance is one of the parameters in the leakage reactance calculation. The slot leakage reactance is indirectly proportional to the number of rotor slots.

8. What is the relation of the zigzag reactance with the specific permeance for zigzag leakage?
a) zigzag reactance is directly proportional to the specific permeance for zigzag leakage
b) zigzag reactance is indirectly proportional to the specific permeance for zigzag leakage
c) zigzag reactance is directly proportional to the square of the specific permeance for zigzag leakage
d) zigzag reactance is indirectly proportional to the square of the specific permeance for zigzag leakage

Explanation: Zigzag reactance is one of the parameters used in the leakage reactance calculation. The zigzag reactance is directly proportional to the specific permeance for zigzag leakage.

9. What is the relation of the stator slot leakage factor with the skew leakage reactance?
a) skew leakage reactance is directly proportional to the stator slot leakage factor
b) skew leakage reactance is indirectly proportional to the stator slot leakage factor
c) skew leakage reactance is directly proportional to the square of stator slot leakage factor
d) skew leakage reactance is indirectly proportional to the square of stator slot leakage factor

Explanation: Skew leakage reactance is one of the parameters used in the leakage reactance calculation. The skew leakage reactance is directly proportional to the stator slot leakage reactance.

10. What is the formula for the rotor bar skew angle?
a) rotor bar skew angle = 3.14 / rotor slot pitches through which bars are skewed * (no of rotor slots / number of poles)
b) rotor bar skew angle = 3.14 * rotor slot pitches through which bars are skewed * (no of rotor slots * number of poles)
c) rotor bar skew angle = 3.14 * rotor slot pitches through which bars are skewed / (no of rotor slots * number of poles)
d) rotor bar skew angle = 3.14 * rotor slot pitches through which bars are skewed / (no of rotor slots / number of poles)

Explanation: The rotor slot pitches through which bars are skewed, number of rotor slots and number of poles are calculated. On substitution the rotor bar skew angle is obtained.

11. What is the value of the stator slot leakage factor?
a) 0.90
b) 0.80
c) 0.95
d) 0.85

Explanation: Stator slot leakage factor is used in the calculation of the skew leakage reactance. The value of the stator slot leakage factor is 0.95 in the single phase induction motor.

12. What is the relation of the overhang leakage reactance with the average coil span in slots?
a) overhang leakage reactance is directly proportional to the square of the average coil span in slots
b) overhang leakage reactance is indirectly proportional to the square of the average coil span in slots
c) overhang leakage reactance is directly proportional to the average coil span in slots
d) overhang leakage reactance is indirectly proportional to the average coil span in slots

Explanation: The overhang leakage reactance is one of the parameters used in the leakage reactance calculation. The overhang leakage reactance is directly proportional to the average coil span in slots.

13. What is the relation between pole pitch and the magnetizing reactance?
a) magnetizing reactance is directly proportional to the square of the pole pitch
b) magnetizing reactance is directly proportional to the pole pitch
c) magnetizing reactance is indirectly proportional to the pole pitch
d) magnetizing reactance is indirectly proportional to the square of the pole pitch

Explanation: The magnetizing reactance is one of the parameters in the leakage reactance calculation. The magnetizing reactance is directly proportional to the pole pitch.

14. The magnetizing reactance is directly proportional to the saturation factor.
a) true
b) false

Explanation: The magnetizing reactance is one of the components used in the leakage reactance calculations. The magnetizing reactance is indirectly proportional to the saturation factor.

15. What is the formula of the saturation factor?
a) saturation factor = total mmf required for magnetic circuit * mmf required for air gap
b) saturation factor = total mmf required for magnetic circuit – mmf required for air gap
c) saturation factor = total mmf required for magnetic circuit / mmf required for air gap
d) saturation factor = total mmf required for magnetic circuit + mmf required for air gap

Explanation: The total mmf required for the magnetic circuit and the mmf required for air gap is calculated. On substitution of the values the saturation factor is calculated.

16. What factor is the core length made equal to in theoretical conditions?
a) pole length
b) pole proportion
c) pole length
d) number of poles

Explanation: The core length is made equal to the pole length in theoretical conditions. But in practical the exact dimensions are governed by manufacturing conditions.

17. What is the output equation of a single phase induction motor developed by P.H Tricky?
a) diameter2 * length = 16.5 / H.P * output coefficient * frequency constant * motor type constants * rpm * 106
b) diameter2 * length = 16.5 * H.P * output coefficient * frequency constant * motor type constants /rpm * 106
c) diameter2 * length = 16.5 * H.P / output coefficient * frequency constant * motor type constants * rpm * 106
d) diameter2 * length = 16.5 * H.P * output coefficient / frequency constant * motor type constants * rpm * 106

Explanation: The output coefficient, horse power, frequency constant, motor type constant along with the speed is calculated. On substitution we get the diameter2 * length value.

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