I am trying to work out how to wire up this A/C motor. There are three wires and one of the wires (Wire 1) has a marking (Z2). Two of the wires have terminals (wire 1 & 2) and the third wire has been cut. Wire 2 also has a jumper wire which has also been cut.

After having looked at other fan wiring diagrams I see a lot of them refer to a capacitor but I am unsure whether this motor needs a capacitor and if it does what type and size of capacitor and where would it be wired with this motor.


My initial thoughts were that maybe there was a capacitor that went between the cut wires but without any markings or wiring diagram I am at a loss.

  • \$\begingroup\$ Do you have the confidence to open the rear cover without causing damage? A peek inside would confirm if it is a universal brush motor or some king of induction motor. Usually small motors that require a run- or start-capacitor have it bolted on the side or mentioned on the nameplate. One wire MAY be a protective earth, test with ohm meter. \$\endgroup\$
    – KalleMP
    Sep 4 '16 at 18:01
  • \$\begingroup\$ The fact tat the speeds mentioned are about 10% below synchronous for 50 and 60Hz suggests an induction motor, not brushed.Whether it's a run capacitor or something like shaded pole is another question. Try resistance measurements between wires. If it needs a capacitor, there will be 2 windings of similar resistance; the lower resistance one being directly connected. If one resistance is 10% of the other, that might be a 20V tap to adapt the motor for 250V rather than 230V. As Kalle says, connections under teh cover may help. \$\endgroup\$ Sep 4 '16 at 18:22

Because there are only two wires with terminals at the end I am assuming it is single phase. If this is the cause, it doesn't matter how you hook up which wire goes to positive and which goes to ground. It will work fine either way.

If this is a 3 phase motor (I don't think it is) you can tell which phase is which by the amount of resistance between the wires.

As far as the capacitor you usually see on motors, that is to help with in rush current. The capacitor can be charged before hand and when the motor is starting the capacitor can help supply current so the motor doesn't draw as much current on start up.

  • \$\begingroup\$ This is obviously a single phase motor (data plate says PH 1). Additionally, for a single-phase motor, the capacitor is typically not used to limit inrush current, but to provide a phase shift for another winding in the motor. \$\endgroup\$ Sep 5 '16 at 3:39

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