Red Seal Electrician Practice
TransformersQuestion 1127 of 1506

In a saturable reactor, what does an increase in the DC control current do to the AC load current?

  1. It raises the inductance, which lowers the AC load current.
  2. It has no effect on the AC power winding, only on the DC supply.
  3. It changes the AC frequency that is sent to the load.
  4. The core saturates, so inductance falls and load current rises.
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Correct answer: The core saturates, so inductance falls and load current rises.

More DC flux saturates the core. A saturated core has less inductance and less impedance, so more AC current flows.

Source: Lessons in Electric Circuits II: AC (Kuphaldt), 10.7: Special Transformers and Applications

Practice transformers

Questions last reviewed: 18 October 2026