# Design of Electrical Machines Questions and Answers – Stator Winding

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

1. What type of winding is generally used for the stators?
a) double layer wave winding
b) double layer lap winding
c) single layer wave winding
d) single layer lap winding

Explanation: The double layer wave winding is generally used for stators. The wave winding is with diamond coils is used for stators.

2. What type of winding is made use of small motors?
a) single layer mush winding
b) single layer lap winding
c) single layer wave winding
d) double layer wave winding

Explanation: Small motors consisting of small number of slots have a large number of turns per phase. These small motors use single layer mush windings.

3. What class does the slot and phase insulation belong to?
a) B
b) Y
c) H
d) E

Explanation: The modern insulating materials for diamond coils belong to class E, B and F. The slot and phase insulation is Polyester foil coated with compressed fibre for Class E.

4. What class does the plastic foil baked with polyamide fibres belong to?
a) Y
b) B
c) F
d) H

Explanation: The modern insulating materials for diamond coils belong to classes E, B, and F. The plastic foil baked with polyamide fibres belong to class F.

5. What is the formula for flux per pole?
a) flux per pole = average magnetic flux * pole pitch * length
b) flux per pole = average magnetic flux / pole pitch * length
c) flux per pole = average magnetic flux * pole pitch / length
d) flux per pole = average magnetic flux * pole pitch + length

Explanation: First the average magnetic flux is calculated. Then the pole pitch is calculated and then the length of the pole is calculated.

6. What is the initial assumption for the value of winding factor?
a) 0.9
b) 0.95
c) 0.93
d) 0.92

Explanation: The winding factor may be initially assumed as 0.955. It is the value of winding factor for infinitely distributed winding with full pitch coils.

7. What is the formula for stator turns per phase?
a) stator turns per phase = Stator voltage per phase / 4.44 * f * maximum flux / stator winding factor
b) stator turns per phase = Stator voltage per phase * 4.44 * f * maximum flux * stator winding factor
c) stator turns per phase = Stator voltage per phase / 4.44 * f * maximum flux * stator winding factor
d) stator turns per phase = Stator voltage per phase * 4.44 * f * maximum flux / stator winding factor

Explanation: For the finding out of stator turns per phase, first the stator voltage per phase is obtained. Next, the maximum flux is calculated, then the stator winding factor is calculated.

8. What should be the range of current density in the stator windings?
a) 2-5 A per mm2
b) 4-5 A per mm2
c) 3-5 A per mm2
d) 2-3 A per mm2

Explanation: The minimum value for the current density in stator winding is 3 A per mm2. The maximum value of the current density in the stator windings should not exceed 5 A per mm2.

9. For the lower values of current, round conductors would be convenient to use.
a) true
b) false

Explanation: For lower values of current, round conductors would be the most convenient to use while for higher current bars. It should be less than 2 or 3 mm in diameter or else it is difficult to wind.