Placement - online test I (transformers)

1. Which part of a transformer is responsible for reducing hysteresis loss?

• a) Copper windings

• b) Laminated core

• c) Oil cooling system

• d) Breather

Answer explanation

(b) Laminated core → Laminations reduce hysteresis and eddy current losses, improving efficiency.

2. 2. What happens if the secondary winding of a transformer is open-circuited?

• a) Primary current becomes zero

• b) Transformer will burn

• c) No power is transferred to the secondary

• d) Transformer efficiency increases

Answer explanation

(c) No power is transferred to the secondary → With an open secondary, no current flows, and power transfer stops.

3. Why is the tertiary winding used in a three-winding transformer?

• a) To improve efficiency

• b) To reduce voltage fluctuations

• c) To stabilize unbalanced loads

• d) To increase leakage reactance

Answer explanation

(c) To stabilize unbalanced loads → The tertiary winding helps in load balancing and voltage stabilization in three-phase transformers.

4. Which material is commonly used for transformer core to reduce losses?

• a) Copper

• b) Aluminum

• c) Cast iron

• d) Silicon steel

Answer explanation

(d) Silicon steel → Silicon steel has low hysteresis loss and high permeability, making it ideal for transformer cores.

5. Why is a Buchholz relay used in transformers?

• a) To measure voltage regulation

• b) To protect against internal faults

• c) To improve insulation

• d) To step up voltage

Answer explanation

(b) To protect against internal faults → The Buchholz relay detects gas formation due to internal faults and prevents transformer damage.