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In this circuit: enter image description here

Is the transformer and the circuit on the secondary side of the transformer only there for the test-point or does it affect the voltage to the DC motor?

The DC motor is a 90V motor and the AC signal that is switched on with the relay is a 120VAC signal.

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That's a current transformer. You may not disconnect the load on a secondary side. The circuit is for measuring the motor current, it does affect the DC voltage of the motor, but this voltage drop is neglible. If you want to eliminate it you have to short circuit points 3 and 4. You may never disconnect the secondary 1,2 or eliminate the resistances R46 or R47.

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  • \$\begingroup\$ So I can remove the circuit on the secondary side and the transformer itself and still expect the same operation of the motor? \$\endgroup\$ – user41391 Jul 22 '16 at 18:58
  • \$\begingroup\$ @Coffee Well, I don't know the purpose of current measuring. \$\endgroup\$ – Marko Buršič Jul 22 '16 at 19:00
  • \$\begingroup\$ I understand thanks. But assuming it was just for testing and debugging, then it would be the same, right? \$\endgroup\$ – user41391 Jul 22 '16 at 19:02
  • \$\begingroup\$ @Coffee NO! You must have termination on the secondary side at all times! \$\endgroup\$ – winny Jul 22 '16 at 20:03
  • \$\begingroup\$ @winny Ok, but in my comment I mentioned taking out the transformer, so there will not even be a secondary side? \$\endgroup\$ – user41391 Jul 22 '16 at 20:08
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T1 is a current transformer, so the primary is normally one turn of a heavy gauge wire. It has no effect on the motor at all. The test point you mentioned indicates the current the motor is consuming, but without more information I do not know what the volts per amp reading is.

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