BLDC or 3-phase-AC for mill motor replacement ?

[maxime.levesque]

Have you considered a VFD? It would allow you to run the 3 phase motor on single phase 220, and even give you a bit more RPM range. They can be purchased for as little as $100.

The VFD is my preffered option, the difficulty is finding a replacement motor. I did a VFD conversion for a lathe (Hardinge HLV), it was quite easy, (lots of room in the cabinet for an adapter plate, a pulley can easily be turned, etc). For this mill it will be more challenging, il will most likely need a working mill to make the adapter.

 

[maxime.levesque]

I wanted to do this at one point, but the transformers were quite expensive. I went the VFD route for a lathe and I was quite happy with the added features (variable speed, break, jog function, etc). I don't plan on having more than 3 or 4 machines, so I won't be saving much with a "575v electrical factory" for the trouble.

What are your longer term plans? If you get a phase converter (couple good options for this first step) + a transformer, then you can simply connect the machine and away you go. Then any other 240 or 575 three phase machines are easily powered up. Three phase and higher voltage machines tend to be higher quality (numerous exceptions aside) and there is less competition, because folks have a hard time sorting out the power. The venerable RPC is one good option, and they are quite easy to make yourself (many people here on HM have done so and can direct you to the plans to make one), then a small transformer can be purchased used (may have to be patient). If you are handy at putting electrical stuff together, and with some searching and patience, it can be done pretty inexpensively.

This arrangement works well (I have been using such a set up for about 10 years, have quite a few machines hooked up to it). You may well be able to do a motor swap and VFD cheaper - but still not cheap, cheap - it is a chore to match up the motor and only addresses that machine.

 

[woodchucker]

Not great, which is why I'm trying to find a used replacement motor before, to know the real cost beforehand.

There are many nice used mills at great price, but unfortunately most of them are too big.
I can only have a bench mill, as I will have to move it to my basement.
Bench mills are much more expensive for their weight and quality, there are too many of us basement machinists, we drive up the demand !

Not Great, then why bother, keep looking.

 

[PNW_Guy]

The VFD is my preffered option, the difficulty is finding a replacement motor. I did a VFD conversion for a lathe (Hardinge HLV), it was quite easy, (lots of room in the cabinet for an adapter plate, a pulley can easily be turned, etc). For this mill it will be more challenging, il will most likely need a working mill to make the adapter.

I'm confused and must have missed something.
If you use a VFD, why would you replace the motor?

 

[woodchucker]

I'm confused and must have missed something.
If you use a VFD, why would you replace the motor?

because its a 575v motor on there now.
He can only provide 220v, so VFD won't solve that.

 

[PNW_Guy]

because its a 575v motor on there now.
He can only provide 220v, so VFD won't solve that.

Ahh, for some reason I was thinking that 575v was a model number or frame size. I've never run across a 575 volt motor.

 

[Beckerkumm]

That is a weird motor plate. 2850 is a 50hz motor but 1730 is a 60hz designation. Either way, a two speed motor usually has a large frame so as Mark advised, replacing and fitting may be difficult. I've been down the 575v rabbit hole ( even made my own transformer from three single phase 240-600 units found cheap ) but high voltage is not for the faint hearted. I'd only attempt it if the machine was special, rare, or like new. Dave