Except for distribution transformers, power transformers are often made to be as powerful as possible around:
A. Half-load
B. No-load
C. Near full-load
D. 10% overload
Transformers
A transformer’s full-load copper loss is 1600 W. The copper loss at half-load is:
A. 800 W
B. 400 W
C. 1600 W
D. 6400 W
Which types of winding is used in a shell-type transformer with three phases ?
A. Sandwich type
B. Rectangular type
C. Cylindrical type
D. Circular type
What is the main requirement for transformers used in electronic applications ?
A. Perfect DC isolation
B. Maximum efficiency
C. Constant amplitude voltage gain
D. Perfect DC isolation, maximum efficiency and constant voltage gain
With a turn ratio of 0.4 and a 20kVA transformer, how much total power is transferred inductively ?
A. 50kVA
B. 12kVA
C. 10kVA
D. 8kVA
What is the main advantage of an auto-transformer compared to a two-winding transformer ?
A. Copper losses are negligible
B. Hysteresis losses are reduced
C. Eddy losses are totally eliminated
D. Saving in winding material
The concept of welding transformers is that a weld is actually:
A. short circuit
B. circuit with finite reactance
C. open circuit
D. circuit with finite resistance
What happens if a current transformer’s secondary is open-circuited ?
A. cool as there is no secondary current
B. hot because primary will carry heavy current
C. hot because of heavy iron losses
D. depends on other parameters
Which of the following testing for transformers is not standard procedure ?
A. Radio interference test
B. Impedance test
C. Polarity test
D. Core insulation voltage test
Why are large power transforming applications using shell type three-phase transformers ?
A. More height and less height flexibility
B. Can be made with more height
C. Due to other reasons
D. Can be made with less height