Powering a DC Motor

[Gold]

I have 1/50th hp DC motor that takes a 115VDC input. I want to power it up and see it spin before buying a speed controller. The motor has a tachometer attached so I’d also like to measure the output of the tacho to get the right speed controller.

I don’t have a DC power supply that can output 115VDC. Can I feed it a raw DC output from a bridge rectifier? How should I do it?

 

[abbey road d enfer]

I have 1/50th hp DC motor that takes a 115VDC input. I want to power it up and see it spin before buying a speed controller. The motor has a tachometer attached so I’d also like to measure the output of the tacho to get the right speed controller.

What are the connections to this motor? Where does it come from?
Brushless or "brushwith"? Is there an indication of nominal speed?

I don’t have a DC power supply that can output 115VDC. Can I feed it a raw DC output from a bridge rectifier? How should I do it?

If it's "universal" motor, it should run on AC as well as DC. But I suspect it's not that. Just remember that 115Vac rectified and smoothed is 162Vdc.
If it's a multipole motor, it takes a multiple-phase signal delivered by an electronic controller. The ones I know (knew) are generally low voltage (<48V)

 

[Gold]

What are the connections to this motor? Where does it come from?

It’s a Bodine motor with a Minarik tachometer. Both companies are still in business. Minarik makes speed controllers too. I called Minarik and they suggested powering it up and measuring the tacho output.
The connections are seven unlabeled spade lugs at the end of the cable.

Brushless or "brushwith"? Is there an indication of nominal speed

It has brushes. The technician said I should remove the brushes and measure DC resistance. Then I can figure out the spade lugs.

The speed of the motor is 1750RPM with a 1:18 speed reducer. It was used to drive the leadscrew of a Neumann AM131 lathe. There is a home brew speed controller but I don’t want to try it. Since the manufacturer is still in business I ‘ll go with that.

If it's "universal" motor, it should run on AC as well as DC. But I suspect it's not that. Just remember that 115Vac rectified and smoothed is 162Vdc.

I have a variac and can measure the output of a rectifier. There are seven terminated wires. I guess I should get the detailed specs on the motor from Bodine. There are only two brushes that I could see. I could look for another one.

 

[abbey road d enfer]

It has brushes. The technician said I should remove the brushes and measure DC resistance. Then I can figure out the spade lugs.

AFAIK, a permanent magnet motor has only two poles, one for each brush. One is probably earth/chassis. The other 4 are a kind of mystery. There may be connections for an overtemperature detector...
The wiring dgm for model 0039 shows only 3wires...

 

[Gold]

I guess I’ll try find the two ends of the motor coil by measuring DC resistance at the brushes. Then find the leads that match. Then feed it 115VDC through a fuse and try to find the tacho voltage on other leads.

 

[gyraf]

A brushed dc motor will most often start and run happily from less than 1/4 of its rated voltage. Try with whatever you have at 50v or thereabout.

Remember you can stack different supplies as long as you dont short Them.

..or use a small stack of 9v batteriets, they series connect easily

Jakob E.

 

[Gold]

A brushed dc motor will most often start and run happily from less than 1/4 of its rated voltage. Try with whatever you have at 50v or thereabout.

Thanks, I’ll see what I have laying around. I think I have an HP supply that goes to 50V.

 

[abbey road d enfer]

A brushed dc motor will most often start and run happily from less than 1/4 of its rated voltage.

Actually it's the only way to control speed electronically.

 

[cyrano]

Some motors require a whole lot more current to start than their power rating would suggest.

I have a 24V 5A precision motor that requires about 50A peak to start. Once started, it's happy with less than 5A even when pulling a load. I believe it came out of a lathe. It's Russian/Finnish...

Your average DC lab power supply just isn't capable of spinning up some motors. Current limiting, back-EMF etc. I use lead-acid batteries in such case.

 

[abbey road d enfer]

Some motors require a whole lot more current to start than their power rating would suggest.

I have a 24V 5A precision motor that requires about 50A peak to start.

Weird.

Once started, it's happy with less than 5A even when pulling a load. I believe it came out of a lathe. It's Russian/Finnish...

What type of motor is it? Brush-type?

 

[cyrano]

It's a classic brushed DC motor. Bought a pair from a guy who builds 1/6th scale tanks and army trucks. The kind kids can get in and drive around.

It's far too big for its power. 25 cm diameter, 40 cm long or thereabouts. I guesstimate it to be around a third of a horse. Built to last? It draws almost 5A with no load. Still works down to 6V. Amazingly still has torque at 6V.

Could've known it wasn't a power beast. Didn't look at the size of the brushes when I bought it. Still, it was cheap, 30€ for the pair.

 

[Gold]

I have two HP dual 20V supplies. I can feed it 80V at 3A. This motor is 1/50th hp so about 15 Watt. 80V at 3A is 240 Watt.

 

[Gold]

I misremembered what I had. It was a dual 40VDC at 0.3A That’s not enough power. I could feed it raw DC from a rectifier or order a couple of cheap 48VDC PSU’s. A 15W 48VDC is $10 so it’s in the budget.