# Design of Electrical Machines Questions and Answers – Temperature Rise and Insulating Materials

This set of Design of Electrical Machines Interview Questions and Answers focuses on “Temperature Rise and Insulating Materials”.

1. How many number of insulation classes are present with respect to electrical equipment?
a) 5
b) 6
c) 7
d) 8

Explanation: There are 7 classes of insulation with respect to electrical equipment. They are Class Y, Class A, Class E, Class B, Class F, Class H, Class C.

2. How many classes have their temperatures above 100°C?
a) 5
b) 6
c) 7
d) 8

Explanation: There are 7 insulation classes present in relation with temperature. Of the 7 classes, there are 6 classes whose temperatures are greater than 100°C. Class Y is the only class having temperature less than 100.

3. How many classes have their temperatures above 150°C?
a) 2
b) 3
c) 4
d) 5

Explanation: Of 7 classes of insulation, there are 3 classes whose temperatures are above 150°C. They are classes F, H, C of insulation.

4. Which class has the lowest and the highest temperature?
a) Class Y, Class C
b) Class Y, Class H
c) Class H, Class C
d) Class B, Class H

Explanation: Class Y belongs to the lowest insulation class of having temperature of about 90°C. Class C is the highest insulation class of having temperature above 180°C.

5. Class A has higher temperature than Class E.
a) True
b) False

Explanation: Class E has a higher temperature than that of Class A. The temperature of Class A is 105°C and the temperature of Class E is 120°C.

6. What is the temperature of Class B?
a) 120°C
b) 130°C
c) 155°C
d) 180°C

Explanation: 120°C refers to the temperature of Class E. 155°C refers to the temperature of Class F. 180°C refers to the temperature of Class H.

7. Which among the following is the example of Class Y?
a) Varnish
b) Insulation oil
c) Paper
d) Resins

Explanation: Varnish is an example of Class A. Even insulation oil is an example of Class A. Resins is an example of Class E.

8. Which among the following is the example of Class B?
b) Hard fiber
c) Wood
d) Impregnated oil

Explanation: Impregnated oil is the example of Class H. Hard Fiber is the example of Class Y and Wood is the example of Class A.

9. Which among the following is an example of Class F?
a) Paper lamination
b) Nitrile rubber
c) Asbestos
d) Silicone

Explanation: Paper lamination is the example of Class E. Nitrile Rubber is the example of Class A. Asbestos is the example of Class B.

10. Silicone rubber is an example of Class H.
a) True
b) False

Explanation: Class H is one of the insulation classes having temperature about 180°C. Silicone rubber is one of the examples of Class H.

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To practice all areas of Design of Electrical Machines for Interviews, here is complete set of 1000+ Multiple Choice Questions and Answers.