Would this motor work for adding a VFD to a Rong-Fu mill?

[ARC-170]

I have a motor from a treadmill. I've heard these can work for mills and lathes.

This one isn't very big (about 3" in diameter and about 8" long). It's 2HP, 4400 RPM, 90V DC. It's still hooked up to the treadmill.

I can fabricate a amounting bracket (I do have a mill!), but I thought I would see if this motor would even work well.

Thanks!

 

[DavidR8]

I don't know what you need to run that but you don't need a VFD for that motor as it's DC not AC.
A quick google search revealed this:

 

[Hawkeye]

Once you get your DC speed control working, make sure you actually measure the RPM. You'll be using different combinations of pulleys than the original chart on the mill, since the DC motor runs at a higher maximum speed than the original. Especially if the original was a 1725 RPM.

 

[C-Bag]

I personally would not go DC because it’s gets its speed control through voltage variation. So the slower you go the weaker it gets. 3ph doesn’t suffer from this as bad.

 

[RJSakowski]

I personally would not go DC because it’s gets its speed control through voltage variation. So the slower you go the weaker it gets. 3ph doesn’t suffer from this as bad.

I have a 2.5 hp DC 4000 rpm motor on my lathe and a custom built controller. I have usable torque down to 40 rpm for a 100:1 ratio. This is due to using an encoder and feedback to drive a PWM supply.

 

[mattthemuppet2]

If you can use the controller from the treadmill and it's all free, why not? I've done it to all my machines and they work very well. Not as good as a VFD and 3ph motor, but I'm happy with them. The loss of torque at low motor speeds is definitely an issue, but one that you can get around by changing belts to keep the motor in its 40-80% sweetspot. You will need a smaller motor pulley though, as these run over twice as fast as regular single phase motors on mills.

That almost certainly isn't a true 2hp motor, I'd bet on around 1hp or maybe a little more. Should be a good fit for a benchtop mill.

 

[markba633csi]

DC motors have good torque at low speeds if the controller is sophisticated enough. Most treadmills have decent controllers.
KB electronics makes a good aftermarket control also, I'm using one on my lathe
I suspect that motor isn't truly 2 horsepower- more like 1 hp or thereabouts. Treadmill builders like to exaggerate, it sells machines
-M
ps A line-operated dc motor control isn't the same as a VFD (variable frequency drive) as the frequency is fixed at 120 Hertz; the phase angle is adjusted to vary the speed.

 

[ARC-170]

Thanks for the replies! So, I'm looking for a DC speed controller, correct?

SPEED CONTROLLERS
I found this one. It's a bit pricey, though.

This one is about $100 and I have a coupon!

Lastly, this one is $24. What's the difference? I'm not fond of the white.

Would any of these work? What am I looking for?

INSTALLATION
To hook this up, it is a matter of mounting the motor and controller to the mill, then going from the plug to the controller to the motor?

I've looked into a VFD before and was thoroughly confused. I only know a little about electricity, and many of the explanations were heavy on technical terms.

Thanks for any help you can give me.

 

[ARC-170]

If you can use the controller from the treadmill and it's all free, why not? I've done it to all my machines and they work very well. Not as good as a VFD and 3ph motor, but I'm happy with them. The loss of torque at low motor speeds is definitely an issue, but one that you can get around by changing belts to keep the motor in its 40-80% sweetspot. You will need a smaller motor pulley though, as these run over twice as fast as regular single phase motors on mills.

That almost certainly isn't a true 2hp motor, I'd bet on around 1hp or maybe a little more. Should be a good fit for a benchtop mill.

Thanks.

Is the 40-80% sweet spot RPM?

I didn't think it was really 2HP, either!

 

[ARC-170]

DC motors have good torque at low speeds if the controller is sophisticated enough. Most treadmills have decent controllers.
KB electronics makes a good aftermarket control also, I'm using one on my lathe
I suspect that motor isn't truly 2 horsepower- more like 1 hp or thereabouts. Treadmill builders like to exaggerate, it sells machines
-M
ps A line-operated dc motor control isn't the same as a VFD (variable frequency drive) as the frequency is fixed at 120 Hertz; the phase angle is adjusted to vary the speed.

Is the KB electronics controller this one? I'll have to check if this motor has a capacitor start and run, since this one can't be used with those features.