Static phase converter

Hi, just bought a M300 lathe and soon I will be looking for a phase converter.

I have looked at the static Transwave's and also our local machine mart has there's on offer, when I spoke to there technical guy he said there static converters only have power on 2 phases and gets the other phase from the motor, is that right?, I thought my lathe would need all 3 phases.

Thanks in advance

I think static converter from Machine Mart during a 'vat free' period is a good option if your motor is 415v only (415 VFDs cost a lot more) and operates in a harsh environment (vfds don't like metal grinding dust) and you don't need speed control. You do need to match it to the motor. Mine just worked without having to know where the extra phases come from.

I was about to reply but realised I'd already done it on Madmodder!

If you can, a much better option would be a VFD, it's smaller, probably cheaper, and gives you variable speed. It may need the motor to be changed from star to delta wiring to run on 240V - but it might need that anyway. The VFD can be tucked away from swarf etc.

Martin, as John says, if the motor can be reconfigured to 240v 3-phase then a VFD is definitely the way to go. It is probably 415v at the moment if it came from a 415v 3-phase workshop. There will be lots of threads about to help you take the cover off and work out if it can or can't be changed by swapping three wires - just Google search.

Only use a static converter if the motor cannot be changed and you don't want to replace it. They work but people don't like them for various reasons and they are not cheap. You will also need a reasonably large one, probably 3HP minimum.

Thanks guys, I used a M300 when I worked at the railway and to be honest it was fine on a normal 3 phase supply and fixed motor speed. The guy that sold me the lathe used it on a Transwave rotary converter but he wanted to keep it so it wasn't put in with the deal.

Thanks guys, I used a M300 when I worked at the railway and to be honest it was fine on a normal 3 phase supply and fixed motor speed. The guy that sold me the lathe used it on a Transwave rotary converter but he wanted to keep it so it wasn't put in with the deal.

We have not answered your initial question about how a static converter works. Yes, the Machine Mart chap is right in that two phases are fed, one fully and one partially if I remember, and then the third gets energised as the motor spins. The converter box contains capacitance and inductance bits to generate this and there are setting knobs to make it run 'sweetly'. It means that the converter power rating ought to match the motor reasonably well and that the motor is under extra stress when starting up. A rotary converter already has the spinning motor and therefore its three phase delivery is there all the time and more 'clean'.

Edited By norm norton on 19/12/2017 17:05:07

I had a chat today with the guys at Transwave and they explained a static converter basically like you said in your post. To future proof my workshop they actually recommended a rotary converter around 5-7hp. My Warco mill hadn't had much use so that's hopefully got life left in it so will probably stay 240v. I would like a bigger compressor so if a nice 3 phase one comes up atleast I can run it if I went the rotary route.

Edited By Martin Turner 4 on 19/12/2017 19:25:43

I have a 10hp Transwave rotary converter \nd it runs EVERYTHING in the shop,no messing about. 12"X9" planer,4hp spindle moulder,3hp band saw,lathe,milling machine,the lot !,sometimes two or three machines at the same time.

The more I read about these rotary converters I think it's the way I may go, the guy that sold me the lathe had a Transwave rotary converter, it was a shame he wanted to keep it.

I have two workshops some 50 meters apart so I have two transwave converters they do all I want I'm able to run my lathe and saw at the same time of the same converter , I gained all the information from Mr Moss ? Of transwave at a show some 25 years ago the only downside is the suds pump I changed mine to 240 v

Just out of curiosity do the Transwave rotary converters give you a neutral?

Regards.

David.

Another case of yes, no and maybe!

On the up-side rotary converters 'just work'. On the downside, they're expensive, physically big, noisy, inefficient and stupid. (Being stupid may be an advantage!)

VFD's are small, quiet, efficient, relatively cheap and stuffed with goodies. Speed control is a very good thing. On the downside, they can be complicated to set up, may not work with all motors*, generally shouldn't be be used to power more than one motor, and might come with a manual written in Technical Xhosa!

Dave

* I've read motors made before about 1970 are somewhat more likely to have weaker insulation and/or suffer damage due to earthing through their bearings due to spiky VFD waveforms. Motors less than 50 years old have better insulation and protected bearings.

Also, multispeed motors are less suited to VFDs.

According to the guy I spoke to a Transwave yes the rotary converters give a neutral and all 3 phases.