motor wires

[japcas]

Hi, I have 130 volt dc motor. I have a question about 2 of the wires coming out of it. It has a red and black wire which I assume is for power input. It also has 2 blue wires but I can't figure out what they would be used for. Are they for some sort of built in tachometer readout? Any info would be appreciated.

[bernie l]

Anymore information available, mfg, catalog number, anything? what type of equipment is/was it on?

[J. R. Williams]

I would expect the extra wires to be wired to an over temperature switch.

JRW

[japcas]

The motor is a surplus treadmill motor. It was bought from Surplus Center on the web. The item number was 10-1906.

[darryl]

There's an easy way to tell. If this is a permanent magnet motor, short the red and black wires, then turn the shaft by hand. Then unshort those wires and turn the shaft again. If it's easier this time, you've identified the motor wires. The other two are for a temperature cutout or overload sensor. If they are as large of a gauge as the motor wires, it's probably meant to be wired in series with the motor wires. If they are lighter gauge, then they would go into a relay circuit to control the motor.

Another way of testing your motor is to hook up a car headlight in series with a battery and the suspected motor wires. If the motor starts to turn at all, those are the motor wires. If the wires you are testing are for a sensor of some kind, the headlight will glow as bright as if it were just connected to the battery, and the motor will not respond at all. If those wires are a tacho coil, then the light won't light at all. Don't keep the juice on too long in this case, or you may risk burning the tacho coil out. That's very unlikely, though, since it's usually a high resistance and won't draw much current.

I have a couple of motors where the blue wires are for a temperature cutout.

[This message has been edited by darryl (edited 04-02-2005).]

[japcas]

Thanks Darryl, so I should be o.k. just taping the ends of the two blue wires up and using the red and black wires to hook the power too? I know these may seem like stupid questions, but my knowledge of electricity is not very high. Seems I can figure out about anything mechanical, but electricity baffles me.

[J Tiers]

The treadmill motors DO often have a make and break tach output. The ones that do often were intended to go with the TDA1085 control chip. If you look it up, you can find a schematic for the control circuit in the data sheet.

Sounds like a permanent magnet motor. Treadmill motors are, mostly.

Put yer ohmmeter on teh blue leads and see if they make and break as you turn. Also do teh short test as mentioned, that should tell you which is the power lead pair.

The power leads will also make and break to an extent, but they will also drive the ohmmeter to read nutty resistances due to the generated power as you turn the shaft.

[sch]

If this is an Argord motor, I have the same motor and the blue leads are an over temp switch that is NC, and opens somewhere around
105 deg C. I have fiddled with controllers
for this motor which draws upto 18amps at 130vdc. The Minarik 2311, which Surplus has
sold from time to time had trouble above about 70-80vdc and its internal protection cycled on and off. It is rated upto 10amps.
Next tried SCR full wave and found the motor cogged at low speeds. The 25a FW bridge blew and I discarded that approach. Last experiment was with a dual 555 controller
(about $15 from MPJA at same.com) and I swapped the IRFZ44 for a pair of IRF740 in
parallel and got very good control with a slow speed in the few hundred rpm with reasonable torque. High speed was not measured but above 4000rpm. Motor got too
hot to touch after about 20min so would need
a good fan for cooling and it would be a good idea to use those blue leads to prevent over heating. The controller and fets were about $20 total, fets from Allelectronics.com.
Steve

[darryl]

Steve, I'm wondering about that 25a br, why it blew. Seems there's going to be a br in any controller with a dc output and an ac input. Maybe it didn't have a high enough voltage rating, or it got too hot?
I seem to find all too often that parts have borderline voltage ratings for the circuit in which they're used. I have many times in the past solved a recurring problem by using a higher voltage rated part. Any output device fed from rectified ac should have at least a 600 volt rating, MHO. , and that goes for the br as well.