This set of Design of Electrical Machines Multiple Choice Questions & Answers (MCQs) focuses on “Window Space Factor”.
1. What is window space factor?
a) window space factor = copper area in the window – total window area
b) window space factor = copper area in the window + total window area
c) window space factor = copper area in the window * total window area
d) window space factor = copper area in the window / total window area
View Answer
Explanation: Window space factor is the ratio of the copper area in the window to the total window area. It is a constant used in the output equation of transformers.
2. What does the window space factor depend on?
a) it depends on the core
b) it depends on the armature
c) it depends on the insulation
d) it depends on the insulation and copper
View Answer
Explanation: Window space factor totally depends on the insulation of the machine. It also depends on the copper windings provided.
3. What does the insulation and copper of the transformer depend on?
a) current rating
b) voltage rating
c) output power
d) voltage rating and output power
View Answer
Explanation: The insulation and copper of the transformer depend on the voltage rating of the transformer. It also depends on the output power produced by the transformer.
4. What is the empirical formula for calculating the value of window space factor?
a) window space factor = 10 / (30+kV)
b) window space factor = 5 * (30+kV)
c) window space factor = 10 * (30+kV)
d) window space factor = 5 / (30+kV)
View Answer
Explanation: The output voltage in kV is calculated first. Then the value is substituted in the formula to obtain the empirical value of the window space factor.
5. What is the empirical value of window space factor, given the output is 1000kV?
a) 0.09
b) 0.9
c) 0.009
d) 0.0009
View Answer
Explanation: Empirical value of window space factor = 10 / (30+kV)
kV = 1000 kV, empirical value = 10/1030 = 0.009.
6. What is the ratings of the transformers for using the empirical value of window space factor?
a) 50-100 kVA
b) 50-150 kVA
c) 50-200 kVA
d) 100-200 kVA
View Answer
Explanation: The empirical formula of the window space factor is used for the transformers of the rating 50-200 kVA. If the transformer rating is higher than 200 kVA then the empirical formula isn’t used.
7. What is the relationship of the space factor value with the large and small outputs?
a) small value for both large and small outputs
b) large values for both large and small outputs
c) large value for small output and small value for large outputs
d) small value for small output and large value for large outputs
View Answer
Explanation: The space factor is directly proportional to the output. If large output is obtained, space factor is high and vice versa.
8. What is the formula for the window space factor, when the output is 1000 kVA?
a) 12 / (30+kV)
b) 10 / (30+kV)
c) 9 / (30+kV)
d) 11 / (30+kV)
View Answer
Explanation: 10 / (30+kV) denotes the empirical value of window space factor for rating between 50-200 kilo-volt-amp. When the output is near 1000 kilo-volt-amp then the formula used is 12/(30+kV).
9. What is the formula of window space factor, when the transformer rating is 20 kVA?
a) 10 / (30+kV)
b) 12 / (30+kV)
c) 8 / (30+kV)
d) 19 / (30+kV)
View Answer
Explanation: 10 / (30+kV) denotes the empirical value of window space factor for rating between 50-200 kilo-volt-amp. 12 / (30+kV) is the window space factor for transformers having rating around 1000 kVA.
10. The area of the window depends on the window space factor.
a) true
b) false
View Answer
Explanation: Area of the window = Total conductor area/window space factor.
The area of the window is indirectly proportional to the window space factor.
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