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I have a two speed electric motor fitted to a large pillar drill (Arboga Type) and had a problem where the motor could be started in either direction just by spinning the chuck. High speed also did not appear to be operational.

The motor has 6 wires and the field resistances would appear to be approximately 26 ohms and 16 ohms. Following the logic through the rotary switch it would appear that when either low or high speed is selected the other coil is left open circuit.

If anybody has any knowledge on this type of motor I'd be grateful.

Tags: motor, Induction

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Thanks for taking the time to reply.

I forgot to mention this is a 3 phase unit, low speed is 1440 and high speed is 2900RPM. The motor has 6 wires emanating from the frame with 3 field resistances at approximately 25 ohms and the other 3 at approximately 16 ohms.

It uses a rotary switch with a number of bridges or links to energize the appropriate winding.

Also, here's a good article on 2-speed motors.

https://precisionautomation.ne...on-two-speed-motors/

RM

https://www.allaboutcircuits.c...or-induction-motors/

http://i-gard.com/site/assets/...und_rotor_motors.pdf

https://easa.com/resources/res...und-rotor-windings-1

Now what you describe is a wound rotor motor design

If you take the resistors/speed control out of the picture you can narrow down the problem. Put a short lead on the three slip rings and tie all three leads together. This essentially is causing the motor to operate at high speed with no resistors in the circuit. If the motor behaves as you describe then the motor/rotor windings are shorted, if motor runs ok, either speed, with rings shorted together, then resistor or switch is the problem. My experience tells me what you describe is a single phase problem or shorted winding

Dave

RM

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