What can I do with this motor I found?

Thread Starter

tom66

Joined May 9, 2009
2,595
Bill is correct. I checked the voltage coming out of the red wires. It's AC with a varying amplitude and frequency. Higher amplitude and frequency for a faster speed, and amplitude is approximately proportional to speed (half speed = half RMS voltage.)

It seems to have 10 pulses per rotation, although I haven't precisely measured it.

Once running, the field voltage can *sometimes* be removed. However about 20% of the time, it will stall and then start drawing ~3A.

Strange thing is, it seems to draw about the same current, no matter the voltage, so power is approximately proportional to voltage. It draws about 0.8A - 1.2A unloaded.

It doesn't generate a voltage when rotated without a field voltage.
 

Thread Starter

tom66

Joined May 9, 2009
2,595
I tried to generate a field voltage to run the motor. I used 8x100R resistors, 1/4W each, in parallel to make 12.5 ohm 2W resistor. The motor did start, however very quickly the resistors were in smoke! After 20 seconds they were completely burnt out and the motor did continue, but of course after stalling it would not restart.

What would be the best way to generate the field voltage?
 

strantor

Joined Oct 3, 2010
5,369
Ok, I'm not sure exactly what you are describing. Are you trying to use it as a motor or a generator? You keep referring to field voltage. As I've said, what's important is field current. This type of motor is designed to be ran in series; meaning the field coil is in series with the armature; meaning the current in the field is always the same as the current in the armature. the lesser the current in the field, the faster it spins; seems counterintuitive, but it's true. google 'field weakening'. This is the reason why you never want to run a universal motor with no load. Reduce the load on teh motor, and the current thru the armature drops, which also drops the current thru the field windings, since they're in series. That lowers the magnetic field in the windings, which reduces the "drag" on the armature, which speeds it up, which reduces the current, which reduces the field, which speeds it up.... and so on until it spins itself to destruction.

ok, I may have gotten a little off topic there; what are you trying to do?
 

Thread Starter

tom66

Joined May 9, 2009
2,595
Ok, I'm not sure exactly what you are describing. Are you trying to use it as a motor or a generator? You keep referring to field voltage. As I've said, what's important is field current. This type of motor is designed to be ran in series; meaning the field coil is in series with the armature; meaning the current in the field is always the same as the current in the armature. the lesser the current in the field, the faster it spins; seems counterintuitive, but it's true. google 'field weakening'. This is the reason why you never want to run a universal motor with no load. Reduce the load on teh motor, and the current thru the armature drops, which also drops the current thru the field windings, since they're in series. That lowers the magnetic field in the windings, which reduces the "drag" on the armature, which speeds it up, which reduces the current, which reduces the field, which speeds it up.... and so on until it spins itself to destruction.

ok, I may have gotten a little off topic there; what are you trying to do?
At the moment, I'm just trying to run it as a motor. So I thought the field was supposed to be run at a low current, but obviously I was wrong.

In future I would like to run it as a generator, so when I turn it a voltage is generated, which does not sag under a load, and the voltage is generated without requiring a power supply for the field. The voltage could either be low (10-50V) or high (~300V) but it needs to be one of those.
 

shortbus

Joined Sep 30, 2009
8,043
Unless you can find a way to put magnet in it, it will always need power to the field/stator. In the photos you posed of the motor the label says that it is - 220/240V, 11500 RPM. Both of those will limit the use as a generator. With that voltage rating the wire size of the winding is small compared to a DC motor/gen for 10 - 50V. And the speed rating is going to be hard to reach as a windmill. Motors are designed to work at peak efficiency at the rated values, and fall off fast at around 20% of either side of the design point.
 

strantor

Joined Oct 3, 2010
5,369
At the moment, I'm just trying to run it as a motor. So I thought the field was supposed to be run at a low current, but obviously I was wrong.

In future I would like to run it as a generator, so when I turn it a voltage is generated, which does not sag under a load, and the voltage is generated without requiring a power supply for the field. The voltage could either be low (10-50V) or high (~300V) but it needs to be one of those.
Yeah, the field doesn't always have a small current through it. That's why I've been saying you need to play around with different currents and see what gives you the best output characteristics as a generator. I really have no idea where to tell you to start.

Unless you can find a way to put magnet in it, it will always need power to the field/stator. In the photos you posed of the motor the label says that it is - 220/240V, 11500 RPM. Both of those will limit the use as a generator. With that voltage rating the wire size of the winding is small compared to a DC motor/gen for 10 - 50V. And the speed rating is going to be hard to reach as a windmill. Motors are designed to work at peak efficiency at the rated values, and fall off fast at around 20% of either side of the design point.
yeah, we've been talking about seperating the field from the armature and passing a current through it like an alternator.
I totally missed the RPM rating. that's real high. You would need some step-up gearing to get the motor spinning @ 11500rpm.
 

strantor

Joined Oct 3, 2010
5,369
BTW what are you testing? I only suggested running the motor to verify it works. I think we've verified that; so do you have another motor that you can couple the shafts together and start testing it's generator characteristics? a power drill would work; you could tighten the drill chuck right onto the shaft.
 

Thread Starter

tom66

Joined May 9, 2009
2,595
BTW what are you testing? I only suggested running the motor to verify it works. I think we've verified that; so do you have another motor that you can couple the shafts together and start testing it's generator characteristics? a power drill would work; you could tighten the drill chuck right onto the shaft.
I tried a drill, but the shaft of this motor is about 1.5cm diameter, and my drill chuck doesn't go that big.

For high rpm, I was thinking of a simple pulley system to gear it up. The 1.5cm diameter shaft could be turned by a 15cm diameter pulley. That would provide 10x gearing and be relatively simple to implement.

1150 rpm would be 19.2 Hz rotation rate, so fairly heavy wind.

Either that or hamster power.

OR... I could use it as part of an electric car or go kart, but it doesn't have anywhere near enough output power.
 

strantor

Joined Oct 3, 2010
5,369
I tried a drill, but the shaft of this motor is about 1.5cm diameter, and my drill chuck doesn't go that big.

For high rpm, I was thinking of a simple pulley system to gear it up. The 1.5cm diameter shaft could be turned by a 15cm diameter pulley. That would provide 10x gearing and be relatively simple to implement.

1150 rpm would be 19.2 Hz rotation rate, so fairly heavy wind.

Either that or hamster power.

OR... I could use it as part of an electric car or go kart, but it doesn't have anywhere near enough output power.
you could hook the motor up to a power supply & let it spin; as it spins, you could hold a file to the outside edge of the shaft and mill it down to where your drill chuck can grab it. you only need probably .5cm for you drill chuck to get a good grip.
 
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