Oral Questions - Transformers Flashcards
Name three things you would look for when conducting a visual inspection of a transformer?
- Loose laminations,
- Oil leaks
- Loose terminations
- Condition of windings
- Condition of supports and mountings
- Signs of overheating on no-load conditions.
What is meant by the term, “good continuity” when testing the windings of a transformer?
The windings are continuous from one end to the other.
Describe how you would carry out the continuity test of a transformer winding.
Use an ohmmeter and measure the resistance of the winding.
What is meant by the term “short circuit test” between the windings of a transformer?
Conducting an Insulation resistance test to measure the integrity of the insulation between each winding.
What instrument would you use to carry out a “short circuit” test between the windings of a transformer?
Insulation resistance tester or megger.
Why is it necessary to set the instrument on 500V when testing the insulation resistance of a 240V transformer to earth?
To comply with the appropriate Australian Standard’s (AS/…) .
To stress the dielectric strength of the insulation to twice its working voltage to earth.
If one winding of a step-up transformer had a resistance of 10Ω and the other winding had a resistance of 100Ω, which winding would be the primary?
10Ω
Describe the instrument you would use when testing the winding of a transformer for “shorted turns”?
Ohmmeter, external growler.
List three electrical faults that could occur in a serviceable transformer.
- Insulation resistance to earth,
- insulation resistance between windings,
- shorted turns,
- open circuit winding,
- open circuit connections
List two possible causes for an earth fault in a transformer.
- Low insulation resistance,
- Ingress of moisture,
- Magnetic stresses.
