Electronics > Projects, Designs, and Technical Stuff
Unusual motor circuit
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Excavatoree:
My dad purchased a motor with 6 leads coming from it.  Two go to a capacitor, and the other four go to a double pole relay as shown.

Power is applied to both the relay coil and the common contacts of the relay.  Thus, wires 1 and 3 of the motor don't get power for very long, if at all. (EDIT:  The relay is instantaneous, no delay,  Wires 1 and 3 are powered with the coil that pulls the contacts way from wires 1 and 3)  Power is applied to wires 2 and 4.  I can even bypass the relay and simply apply power to wires 2 and 4 and the motor will turn.

Why on earth would this relay be added to the assembly and connected this way?  There is no information available on the motor, other than what I can see.

Please forgive the crudity of my schematic.  (EDIT)  The motor is AC, pay no attention to the symbol being incorrect.  I needed a symbol with 6 wires, so I very quickly made one from something that looked close.

EDIT:  The motor is multi frequency.  Could a relay be constructed to only switch with low frequency applied to the coil?  Maybe that's it.  I tested at 60 Hz.  Maybe at higher frequency, the relay doesn't do anything, and the other wires are powered.
NiHaoMike:
Probably a strangely wired start relay. The motor might be able to start without it but won't have full starting torque.
Excavatoree:

--- Quote from: NiHaoMike on October 14, 2018, 08:54:21 pm ---Probably a strangely wired start relay. The motor might be able to start without it but won't have full starting torque.

--- End quote ---

I forgot to say the relay has no delay.  When power is applied, it's applied to the common terminals of the relay and the coil at the same time, and the coil switches immediately.  I can't see how powering those two wires for such a brief time can affect anything.    However, I'm totally ignorant, so it may have an effect, somehow, that I just don't realize.
rstofer:
What did the motor come from?  This fact alone may lead to the requirement for the relay.
Is there any possibility that the relay performs dynamic braking by shorting the windings to ground?
amyk:
What type of motor is it? Voltage? Current? Your diagram shows a DC source, but the capacitor suggests it's an AC motor.

Pictures would also be very useful.
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