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

1. What is the formula of the output equation of ac machines?

a) kVA input Q = output coefficient * diameter2 * length * synchronous speed

b) kVA input Q = output coefficient / diameter2 * length * synchronous speed

c) kVA input Q = output coefficient * diameter2 / length * synchronous speed

d) kVA input Q = output coefficient * diameter2 * length / synchronous speed

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Explanation: The output coefficient, diameter, length and synchronous speed are first calculated. Then on substitution gives the kVA input and in turn gives the output equation.

2. What is the formula for the output coefficient of the output equation?

a) output coefficient = 11 * winding space factor * specific magnetic loading / specific electric loading * 10^{-3}

b) output coefficient = 11 * winding space factor * specific magnetic loading * specific electric loading * 10^{-3}

c) output coefficient = 11 * winding space factor / specific magnetic loading * specific electric loading * 10^{-3}

d) output coefficient = 11 / winding space factor * specific magnetic loading * specific electric loading * 10^{-3}

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Explanation: The winding space factor, specific magnetic loading, specific electric loading is calculated. On substitution gives the output coefficient used for the calculation of output equation.

3. What is the formula of the kVA input if the rating of the machine is given in horse power?

a) kVA input = horse power / 0.746 * efficiency * power factor

b) kVA input = horse power * 0.746 * efficiency * power factor

c) kVA input = horse power * 0.746 / efficiency * power factor

d) kVA input = horse power * 0.746 * efficiency / power factor

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Explanation: The horse power rating of the machine along with the efficiency and power factor is calculated. On substitution the kVA input can be obtained.

4. What is the ratio of the efficiency for 75 watt to 750 watt motor?

a) 4:7

b) 5:7

c) 6:7

d) 3:7

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Explanation: The efficiency of the 75 watt motor is 50%. The efficiency of the 750 watt motor is 70%.

5. What is the ratio of power factor of the 75 watt to 750 watt motor?

a) 0.55 : 0.60

b) 0.50 : 0.60

c) 0.55 : 0.65

d) 0.50 : 0.65

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Explanation: The power factor of the 75 watt motor is 0.55. The power factor of 750 watt motor is 0.60.

6. The smaller values are applicable for lower rating machines?

a) true

b) false

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Explanation: The smaller values are applicable for lower rating machines. The power factor is 0.55 for 75 watt motor and the efficiency is 50% for the 75 watt motor.

7. What is the efficiency for the output watt of 180?

a) 0.38

b) 0.48

c) 0.57

d) 0.65

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Explanation: The efficiency of the output watt of 37 is 0.38 and the efficiency of output watt of 90 is 0.48. The efficiency of the output watt of 180 is 0.57.

8. What is the power factor of output watt of 90?

a) 0.46

b) 0.51

c) 0.56

d) 0.62

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Explanation: The power factor of output watt of 37 is 0.46 and the power factor for 180 output watt is 0.56. The power factor of the output watt of 90 is 0.51.

9. What factor does the output coefficient depend upon?

a) specific magnetic loading

b) specific electric loading

c) specific electric loading or specific magnetic loading

d) specific electric loading and specific magnetic loading

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Explanation: The output coefficient depends upon the specific electric loading. The output coefficient also depends upon the specific magnetic loading.

10. What is the range of the average flux density used in the output equation?

a) 0.30-0.55 weber per m^{2}

b) 0.30-0.50 weber per m^{2}

c) 0.35-0.45 weber per m^{2}

d) 0.35-0.55 weber per m^{2}

View Answer

Explanation: The minimum value of the average flux density is 0.35 weber per m

^{2}. The maximum value of the average flux density is 0.55 weber per m

^{2}.

**Sanfoundry Global Education & Learning Series – Design of Electrical Machines.**

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