Font size
WorksheetsTransformer and Harmonic Components Quiz
Total questions: 15
Worksheet time: 22mins
Which of the following contributes to higher impedance?
Short, fat windings
Tall, skinny windings
High turns
Small high/low gap
Which harmonic components are 3 phase with positive rotation?
1st, 7th, 13th
5th, 11th, 17th
3rd, 9th, 15th
Which harmonic components are 3 phase with negative rotation?
1st, 7th, 13th
5th, 11th, 17th
3rd, 9th, 15th
Which harmonic components are single-phase with no phase rotation?
1st, 7th, 13th
5th, 11th, 17th
3rd, 9th, 15th
Current transformers are _______________
parallel connected type of instrument transformers
series connected type of instrument transformers
parallel connected normal transformers
series-parallel connected type of instrument transformers
Which of the following is not a part of transformer installation?
Breather
Conservator
Exciter
Buchholz relay
What is the thickness of laminations used in a transformer?
14 mm to 15 mm
25 mm to 40 mm
0.1 mm to 0.5 mm
4 mm to 5 mm
14. Which of the following transformer, Buchholz’s relay can be fixed on?
a) Welding transformers
b) Oil cooled transformers
c) Auto-transformers
d) Air-cooled transformers
16. An ideal transformer will have maximum efficiency at a load such that _____________
a) copper loss > iron loss
b) cannot be determined
c) copper loss = iron loss
d) copper loss < iron loss
19. A 25 KVA transformer is constructed to a turns ratio of N1/N2 = 10. The impedance of primary winding is 3+j5 ohms and of secondary winding is 0.5+j0.8 ohms. What will be the impedance of transformer when referred to primary?
a) 53 + 85j ohms
b) 53j + 85 ohms
c) Can’t be calculated
d) 3.5 + 5.8j ohms
20. The full-load copper loss of a transformer is 1600 W. At half-load, the copper loss will be _______
a) 1600 W
b) 6400 W
c) 400 W
d) 800 W
22. A power transformer operating at full load draws voltage and current equal to 200 V and 100 A respectively, at 0.8 pf.
Iron and copper losses are equal to 120 W and 300 W.
What is efficiency?
a) 97.44%
b) 99.12%
c) 86.44%
d) 96.44%
What is the formula for voltage regulation?
Vno load(Vno load−Vfull load)⋅100%
Vno load(Vfull load−Vno load)⋅100%
Vfull load(Vno load−Vfull load)⋅100%
Which of the following is the main advantage of an auto-transformer over a two-winding transformer?
a) Eddy losses are totally eliminated
b) Copper losses are negligible
c) Saving in winding material
d) Hysteresis losses are reduced
26. For a 20kVA transformer with a turn ratio of 0.4 what amount of total power is transferred inductively?
a) 10kVA
b) 8kVA
c) 50kVA
d) 12kVA
