I was reading this answer and I would like to understand why if the secondary is short circuited the primary winding will also reflect the short circuit despite the fact that they are isolated. Would the electromagnetic flux through the core be increased with a short circuit on the secondary? If the secondary is shorted I guess it would be as if no turns were present. How would that draw more current from the supply at which the primary is connected?

  • \$\begingroup\$ Not exactly your question, but a dual one: electronics.stackexchange.com/questions/180910/… \$\endgroup\$ – Eugene Sh. Sep 25 '18 at 18:56
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    \$\begingroup\$ Because of the short circuit, the secondary coil will produce a counter magnetic field which eliminates (in an ideal case completeley) the field of the primary coil. \$\endgroup\$ – Oldfart Sep 25 '18 at 19:41
  • \$\begingroup\$ @Oldfart that is fundamentally incorrect or, at best misleading. \$\endgroup\$ – Andy aka Sep 25 '18 at 20:01
  • \$\begingroup\$ @vmms do you understand faradays law of induction? If you don’t then you need to study it before you’ll understand any answer to your current question. \$\endgroup\$ – Andy aka Sep 25 '18 at 20:03
  • \$\begingroup\$ If the secondary is shorted I guess it would be as if no turns were present. You had a valid partial answer in your question. Suggest research to tie all the pieces together. \$\endgroup\$ – user105652 Sep 25 '18 at 20:31

A transformer uses feedback between secondary to primary, via the core flux, and requires some LOW series impedance between the primary voltage source and the voltage across the internal primary N*dphi/dT. Call this voltage the feedback-voltage.


simulate this circuit – Schematic created using CircuitLab


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