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Myford vfd

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John Hilton23/09/2019 08:27:08
96 forum posts
20 photos

Hello.

I have a Myford lathe with a single phase motor.

I want to put a vfd speed control on it, but have struggled to find one that is just single phase. All I can find are 3 phase output ones.

Can anyone help me either to suggest what to look for, or what you are using and how successful it is?

Many thanks

John

John Haine23/09/2019 08:33:38
2700 forum posts
139 photos

I'm afraid you won't find one. Single phase induction motors inherently have only a narrow speed range as they use a capacitor to get the needed phase shift at least for starting and sometimes running too. I believe there are vfds for low power single phase fans but they wouldn't have the grunt needed. You'll need to change the motor to a 3phase one.

Andrew Johnston23/09/2019 08:36:26
avatar
4950 forum posts
563 photos

That's because speed control on a single phase motor doesn't work well. You need to change the single phase motor to a 3-phase motor and then fit one of the many single phase to 3-phase VFDs.

Andrew

Mike Poole23/09/2019 08:45:57
avatar
2189 forum posts
52 photos

As John says you will need to change the motor but it will be well worth it, the machine will be smoother and can be programmed to slow quickly though if you have a clutch then that it not such an advantage. Being able to make slight adjustments to the speed can often improve the finish. Easy reverse is another advantage but be wary of unscrewing the chuck. Complete ready to go packages are available which save some work and provide a well engineered solution, probably not expensive if you build your own to an equivalent standard.

Mike

Baz23/09/2019 09:18:29
269 forum posts

I can thoroughly recommend Newton Tesla’s package, can be easily fitted in under an hour and is a joy to use. Usual disclaimer applies.

Harry Wilkes23/09/2019 10:39:30
avatar
729 forum posts
60 photos

Cant add to anything already said upgraded my S7 to 3phase motor and VFD suppied by Transwave smiley

H

not done it yet23/09/2019 12:40:48
3584 forum posts
15 photos

Just don’t use the VFD as a brake with a screwed chuck. Heavy braking can unscrew the chuck with possible painful consequences.

I have VFDs on my already mechanically-operated variable speed lathe and mill and also on the spindle and table power-feed on my other mill. I wouldn’t want to be without them. Definitely a luxury I can live with!!smiley

John Hilton23/09/2019 13:59:21
96 forum posts
20 photos

Thanks all for your good advice. Now I understand.

Interestingly two if my machines are already 3 phase, which I run from a rotary converter.

Looks like I shall be adding the Myford to the 3 phase list!

John

not done it yet23/09/2019 22:40:00
3584 forum posts
15 photos

VFDs are so much more useful in that they can be programmed to follow all sorts of programable instructions - soft start, variable speed settings, brakes, etc. Also, they don’t use much power when idle and are relatively quiet in operation.

But when dead, they are expensive to get repaired (often cheaper to buy another!). The instruction manuals are often designed for computerised sparkies, not hobbyists, and it’s easy to get it set wrong. I have two which look very similar but each requires the appropriate manual, to avoid programming hiccups. They are not all equal, of course - the more expensive ones having better motor protection, for instance.

Neil Lickfold24/09/2019 06:19:38
575 forum posts
102 photos

What I like best about the VFD and 3 phase motor on my myford is the use of a microswitch for the stop of the lathe when thread cutting. Especially when cutting internal stuff. I know some run it backwards and then feed out, but feeding in knowing that is is going to stop within 0.1mm every time is just great . I have breaking and soft start settings. I put a 3/4 kw motor on my myford about 1hp approx. I just wish I had done it many years earlier. It is smoother running and quieter over all. The smother running shows up in the improved surface finish of parts.

Not cheap , that is true, but well worth it in my view.

Neil

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