Theoretically in transformers, will the secondary voltage increase or decrease (with increasing load current and a lagging load power factor) and why?

  • \$\begingroup\$ It depends how you are driving the transformer's primary winding or, put another way, if the voltage source has a complex impedance, depending on the load, the voltage could rise or fall. \$\endgroup\$
    – Andy aka
    Feb 17, 2017 at 18:05
  • \$\begingroup\$ Primary winding driven by simple AC sinusoidal voltage \$\endgroup\$
    – Psi
    Feb 17, 2017 at 18:08
  • 1
    \$\begingroup\$ Are you happy with the answer I gave? Any doubts or further comments? \$\endgroup\$
    – Andy aka
    Feb 24, 2017 at 9:43

1 Answer 1


Primary winding driven by simple AC sinusoidal voltage

Assuming there are no tuned resonances occuring (due to distributed winding capacitances), if you apply a lagging load (inductive) to the secondary, you can expect the secondary voltage to drop. It might drop a really small amount if the inductive load is many henries or it might drop a lot if the load takes lots of current.

The equivalent circuit of a transformer should confirm my answer: -

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