THEORY - TRANSFORMERS EXAM QUESTIONS WITH CORRECT ANSWERS LATEST UPDATE
2025/2026
How many windings does an 11kV/400V, Delta/Star transformer have? - Answers - Six
What happens with the voltage on the secondary side of an 11kV/400V Delta/Star transformer,
if you reduce the tappings (windings) on the primary side? - Answers - Increase
What is the expected secondary voltage for a voltage (potential) transformer? - Answers - 110V
What is the expected currents for a current tranfromer? - Answers - 1A & 5A
Explain why there should be no fuses on the secondary of the current transformer - Answers - If
open circuited, high voltages may be present causing hazard of electric shock and possible
damage to the CT windings
- Damage to the CT
What does the term burden mean when looking at CT's? - Answers - It's the load (amp meter
and leads) connected to the CT
Eddy Current Loss and Hysteresis Loss are collectively known as - Answers - Iron losses
When transformer windings are carrying current, they heat up. This heating is a loss of energy.
What is this loss of energy known as? - Answers - Copper Loss
How is the core of the transformer manufactured to reduce eddy currents? - Answers -
Laminated plates
How is the core of the transformer manufactured to reduce Hysteresis? - Answers - Use silicon
steel
Why is a transformer rated in kVA and not kW? - Answers - The rating of every transformer is
always given in VA or kVA, which is related to the voltage in the windings
Which protective device will shut down a transformer in the event of an internal loose
connection or arcing, causing gas generation inside the transformer? - Answers - Buchholz relay
What is Hysteresis energy loss due to? - Answers - The magnetising and demagnetising of the
core of a transformer
What are Eddy currents and Hysteresis losses collectively known as? - Answers - Iron losses
What are currents induced into the core of a transformer known as? - Answers - Eddy currents
What is the burden of a current transformer? - Answers - The lead and Amp meter connected to
the CT
2025/2026
How many windings does an 11kV/400V, Delta/Star transformer have? - Answers - Six
What happens with the voltage on the secondary side of an 11kV/400V Delta/Star transformer,
if you reduce the tappings (windings) on the primary side? - Answers - Increase
What is the expected secondary voltage for a voltage (potential) transformer? - Answers - 110V
What is the expected currents for a current tranfromer? - Answers - 1A & 5A
Explain why there should be no fuses on the secondary of the current transformer - Answers - If
open circuited, high voltages may be present causing hazard of electric shock and possible
damage to the CT windings
- Damage to the CT
What does the term burden mean when looking at CT's? - Answers - It's the load (amp meter
and leads) connected to the CT
Eddy Current Loss and Hysteresis Loss are collectively known as - Answers - Iron losses
When transformer windings are carrying current, they heat up. This heating is a loss of energy.
What is this loss of energy known as? - Answers - Copper Loss
How is the core of the transformer manufactured to reduce eddy currents? - Answers -
Laminated plates
How is the core of the transformer manufactured to reduce Hysteresis? - Answers - Use silicon
steel
Why is a transformer rated in kVA and not kW? - Answers - The rating of every transformer is
always given in VA or kVA, which is related to the voltage in the windings
Which protective device will shut down a transformer in the event of an internal loose
connection or arcing, causing gas generation inside the transformer? - Answers - Buchholz relay
What is Hysteresis energy loss due to? - Answers - The magnetising and demagnetising of the
core of a transformer
What are Eddy currents and Hysteresis losses collectively known as? - Answers - Iron losses
What are currents induced into the core of a transformer known as? - Answers - Eddy currents
What is the burden of a current transformer? - Answers - The lead and Amp meter connected to
the CT
