Transformer Testing, High No-load Current

What is the reason for the high no-load current when testing a distribution transformer when switching the mode of the voltage Tap changer of the step-up transformer feeding the tested transformer?

Knowing that the test is done with a constant test voltage each time.

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Some things to check:

  1. Make sure the tap changer is fully engaged. The mechanism could be damaged or making poor contact.

  2. Test for short circuits in the transformer.

  3. Verify no loose connections in the test circuit.

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