A certain amount of current flows when a bank is first energized. This current is known as __________ current.

A certain amount of current flows when a bank is first energized. This current is known as __________ current.

• A. Load current
• B. Magnetizing current
• C. Fault current
• D. Switching current

Answer: (B)

Magnetizing current is the current that flows when a transformer bank is energized with no load. This current is needed to establish the magnetic flux in the iron core through the transformer’s magnetizing inductance, and to supply the core losses (hysteresis and eddy currents). It is largely reactive, meaning it mainly supports the magnetic field, and it exists even before any secondary load is connected. Once a load is applied, the total current becomes the vector sum of this magnetizing current and the load current, so it increases with loading. The other options describe current associated with loading, faults, or switching events, which are not present simply from energizing an unloaded bank.

Magnetizing current is the current that flows when a transformer bank is energized with no load. This current is needed to establish the magnetic flux in the iron core through the transformer’s magnetizing inductance, and to supply the core losses (hysteresis and eddy currents). It is largely reactive, meaning it mainly supports the magnetic field, and it exists even before any secondary load is connected. Once a load is applied, the total current becomes the vector sum of this magnetizing current and the load current, so it increases with loading. The other options describe current associated with loading, faults, or switching events, which are not present simply from energizing an unloaded bank.