Talk to me about rotary phase converters

[mowersman]

Evening all
I bought a new toy today...!

Unfortunately its 3 phase and old enough that the motors cannot be rewired as delta to run on 230v three phase, otherwise I'd have just stuck one of these inverters on it and been done with it. As the 415V inverters are significantly more expensive, I am looking into all the options first.
Looking at rotary phase converters, but the information on the internet is rather confusing and often refers to American sites, where I believe that their 220v is actually 2 phase, rather than our single phase.
Is it possible to build a simple rotary phase converter that will give 415v output from a 230v input, that will give me a reasonable percentage of the motors original power and won't cause it to overheat after 30 seconds!
My other option at the moment is that I have got the motor from the vertical head in bits and it looks like the star connection is easy to get to, so I may split it, solder new wires on and rewire for delta.
Cheers
Andrew

 

[piman]

Hello Andrew,

I would look at the option of changing the motor for a single phase rather than a rotary converter?
Are you sure that it is wired in star as many 415 only motors are delta connected?

Alec

 

[addjunkie]

A rotary phase convertor is basically a static phase convertor, feeding a motor with no load, you then connect your load to that motors terminals.

The induction generated by the no load motor smooths out the manufactured second phase delivered from the static phase convertor.

You can buy them off the shelf but they are expensive. Or you can buy a static one and add the extra motor yourself, still expensive.

It would be cheaper unless you build the convertors, to change the motor to single phase, and rewire machine switches etc. or fit more modern 3 phase motor and vfd.

There is lots of reading on line espescially in model engineering circles.

http://www.practicalmachinist.com/v...ns-101231/?s=8095bc18f0f6f1cc0965e2607234b22b

I think knowing what i know now, if its only a single machine you will have, id go the new motor and vfd route to get the variable speed, if you want to run various bits of 3 phase kit and have a 3 phase supply round your work shop rotary route. At a guess youll get a motor and vfd for under 200 quid for that. If you have power feeds etc, there probably 110, so these also need to be considered.

 

[Newlands]

You probably don't need a new motor - many older 415v motors can be converted to delta to run on 3 phase 220v and you can then use an inverter. Dismantle the motor and have a look at themwindings - you should see where the winding connections are sleeved. If you can see a sleeve with three wires going into it that is probably the star point, ie where the three windings are connected together. All you have to do is unsolder the connection, solder on three tails, cover with a bit of heat shrink and bring them out to the connection box.
I did my lathe motor a while back, thought it was going to be difficult but it was actually very straightforward, link here http://www.model-engineer.co.uk/forums/postings.asp?th=111109 . Bought a chinese vfd from eBay and it runs a treat.
Edit - you've already dismantled the motor ! What are you waiting for?!! A huanyang vfd will cost around £90, but amazingly you have to make sure it's a genuine huanyang, there are cheaper clones that don't use such good components, esp the big output capacitors. Amazingly, because some Chinese companies are cloning other chinese products.

 

[lchris21]

Elliot Omnimill if I'm not mistaken.............???

Co-incidentally I just bought one this week. I've been doing some research as I have the same problem as you. I'm planning on fishing the star point out of the vertical motor and converting it to delta, then running off an VFD. I did it in the past with another mill and it worked great. I'm not planning on using the horizontal spindle so not too bothered about that motor.
Mine also has the powered X-axis like yours, but I'm going to fit a generic 240v powered X-axis motor. That should give a bit more flexibiliy rather than changing the feed gears at the front of the machine??

Fist big job for me is to shorten the vertical over-arm or re-position the motor to the side. I've not got much room in my garage/workshop so want to place the mill as close to the wall as possible. Should save me about 10" in floor space.....not a lot, but when you're jammed in its quite a difference....

I've got a few spare Horizontal arbors if you are interested? I won't be hauling its R'rse away from the wall too often to use the horizontal mill as I nearly had a hernia shifting it the length of the garage yesterday!!!They are 3MT.

Best of luck

 

[mowersman]

A rotary phase convertor is basically a static phase convertor, feeding a motor with no load, you then connect your load to that motors terminals.

The induction generated by the no load motor smooths out the manufactured second phase delivered from the static phase convertor.

You can buy them off the shelf but they are expensive. Or you can buy a static one and add the extra motor yourself, still expensive.

It would be cheaper unless you build the convertors, to change the motor to single phase, and rewire machine switches etc. or fit more modern 3 phase motor and vfd.

There is lots of reading on line espescially in model engineering circles.

http://www.practicalmachinist.com/v...ns-101231/?s=8095bc18f0f6f1cc0965e2607234b22b

I think knowing what i know now, if its only a single machine you will have, id go the new motor and vfd route to get the variable speed, if you want to run various bits of 3 phase kit and have a 3 phase supply round your work shop rotary route. At a guess youll get a motor and vfd for under 200 quid for that. If you have power feeds etc, there probably 110, so these also need to be considered.

Hi, thanks for that. My main reason for considering a rotary converter rather than a VFD is that the Elliott has 3 motors, one for the vertical head, one for the horizontal spindle and the belt driven feed gearbox and the coolant pump. Coolant pump isn't such a worry as it is new and can be wired as delta, so I can just build a simple static phase converter for it. I'd like to keep the two spindles and I see with a VFD you need to wire it directly to the motor, I'd quite like to keep the original switch gear if possible.
I wasn't planning on buyinf a rotary phase converter, I was going to build one, if I can work out how to make one power a 415v motor.

You probably don't need a new motor - many older 415v motors can be converted to delta to run on 3 phase 220v and you can then use an inverter. Dismantle the motor and have a look at themwindings - you should see where the winding connections are sleeved. If you can see a sleeve with three wires going into it that is probably the star point, ie where the three windings are connected together. All you have to do is unsolder the connection, solder on three tails, cover with a bit of heat shrink and bring them out to the connection box.
I did my lathe motor a while back, thought it was going to be difficult but it was actually very straightforward, link here http://www.model-engineer.co.uk/forums/postings.asp?th=111109 . Bought a chinese vfd from eBay and it runs a treat.
Edit - you've already dismantled the motor ! What are you waiting for?!! A huanyang vfd will cost around £90, but amazingly you have to make sure it's a genuine huanyang, there are cheaper clones that don't use such good components, esp the big output capacitors. Amazingly, because some Chinese companies are cloning other chinese products.

Cheers, that link is very helpful! I'll have a closer look today. My only concern with that is can I run both motors from the VFD and can I keep the original switch gear?

Elliot Omnimill if I'm not mistaken.............???

Co-incidentally I just bought one this week. I've been doing some research as I have the same problem as you. I'm planning on fishing the star point out of the vertical motor and converting it to delta, then running off an VFD. I did it in the past with another mill and it worked great. I'm not planning on using the horizontal spindle so not too bothered about that motor.
Mine also has the powered X-axis like yours, but I'm going to fit a generic 240v powered X-axis motor. That should give a bit more flexibiliy rather than changing the feed gears at the front of the machine??

Fist big job for me is to shorten the vertical over-arm or re-position the motor to the side. I've not got much room in my garage/workshop so want to place the mill as close to the wall as possible. Should save me about 10" in floor space.....not a lot, but when you're jammed in its quite a difference....

I've got a few spare Horizontal arbors if you are interested? I won't be hauling its R'rse away from the wall too often to use the horizontal mill as I nearly had a hernia shifting it the length of the garage yesterday!!!They are 3MT.

Best of luckView attachment 75135

Hi, yes, its an Elliott Omnimill, about 1960 as that's what the motors are dated. For my feed, I'm wondering if I can fit a variable speed motor, to give me a nice range of feed speeds. However, I would quite like to keep both motors working, I doubt I'll use the horizontal more than once in a blue moon, but it is just nice to have.
I agree about the length, mine sticks out a long way. I'd be interested to see if you do mount the motor on the side, I may consider doing the same, but I don't want to cut the bar down. Luckily mine was easy to get in, I have lots of easily persuaded mates!
I would certainly be interested in an arbor, as mine didn't come with one. I'll drop you a message theis evening, as I was supposed to be away by now!
Cheers
Andrew

 

[stormin]

Going the VFD route won't stop you running multiple motors as long as at least one is running all the time (main spindle) and the total load doesn't exceed VFD capacity. You would have to bypass the original controls for the motors though. Bit of a pain having to find star points and rewire multiple motors though.
Are you sure main pundke motor isnt multiple speed? That would complicate the internal wiring and reduce chances if successfully converting to delta.

 

[lchris21]

Can't see the main switches on yours? Are they round the side?? Can only see a DOL up front?? I'm going to use the original switches on the front of mine. The last VFD I used had switch inputs so I could use the switch gear off the original control panel. I'm assuming most VFD's have this facility???

 

[ford34/2]

Dave has never failed to please.

http://www.drivesdirect.co.uk/how_to_choose.htm

Stan

 

[Shox Dr]

I bought a 7kva rotary a few yrs ago. Intended it to run multiple machines. In the end I picked up a VFD for the lathe, [mill already had one] and since some scrot nicked my Hydrovane it's never been used/required.

Things to bear in mind are they are noisy, big, very heavy, and take up space.

It's also not a good idea running more than one machine at a time, if you work alone. Not that multiple VFDs stop that practice.

I did have a list of links [I was going to build one] I was going to share but I can't find them at the mo

 

[Chris Stevens]

I bought perfectly working rotary from Ebay for £160, and as it has 15hp motor will power pretty much anything 3 phase. Rotary would very likely be the cheapest route, but there are downsides, and I guess how much you want to spend is going to be pretty important?

 

[Digger6135]

I have a Elliot Omni mill junior it runs quite happily off a Transwave phase converter, the machine has been fitted with a three axis digital read out, and is a very versatile and accurate machine, I'm sure you will be pleased with yours.

Digger6135

 

[Shox Dr]

I bought perfectly working rotary from Ebay for £160, and as it has 15hp motor will power pretty much anything 3 phase. Rotary would very likely be the cheapest route, but there are downsides, and I guess how much you want to spend is going to be pretty important?

What size supply does that need.

 

[Digger6135]

What size supply does that need.

Normal 13 amp domestic supply, the Transwave converter will drive up to 3hp output.

Digger6135

 

[Shox Dr]

Normal 13 amp domestic supply, the Transwave converter will drive up to 3hp output.

Digger6135

Only 3HP that's a poor loss factor?



edit; Digger that question was for Chris not yourself.

 

[Chris Stevens]

What size supply does that need.

Its pretty hefty.......think its at least 30amps, maybe more. Dont use it now though as have workshop with 3 phase, but it was an inexpensive way to be able to use a 5hp Cannings polishing spindle, that cost me £50!

 

[mowersman]

Thanks all, more thoughts for consideration.
I have stripped both motors down tonight and both appear to have very easily accessible star points. Both are also single speed, 440v only 3 phase motors.
So, my current thoughts.
A rotary phase converter would be ideal, but I end up with the hassle of having to build one, or fork out through the nose for an off the shelf one.
So at the moment, I'm thinking of buying a small 230v inverter to run the vertical head once converted.
I have a single phase motor in stock that will bolt in place of the original for the horizontal spindle. It is quite big, so will be a bit inefficient, but I won't be using the feed or the horizontal spindle very much. I also plan to convert the feed to run with a variable speed motor at some point, rather than using the horizontal spindle motor for drive.
Andrew

 

[lchris21]

Hello MM....

just a few pics of the Omnimill fr your interest. I was going to cut down the overarm and shorten it, but its not solid all the way down its length, its got some cast bosses where the rear pulley bracket bolts in. So I decided to make up a plate and position the motor to the side. Saves about 12-14"........

Just got to remember to support the overarm when the pinch bolt is loosened off as its a bit out of balance. Going to make a support bracket for the quill head also, as I've read they can flex a little under a decent cut.

anyway here's what I did to give you some ideas.....

Got my inverter coming in the post so will be getting it running this weekend hopefully...

 

[Shox Dr]

Good move Chris, you'd of kicked yourself sometime in a future if you had cut it down.

 

[brightspark]

Hello MM....

just a few pics of the Omnimill fr your interest. I was going to cut down the overarm and shorten it, but its not solid all the way down its length, its got some cast bosses where the rear pulley bracket bolts in. So I decided to make up a plate and position the motor to the side. Saves about 12-14"........

Just got to remember to support the overarm when the pinch bolt is loosened off as its a bit out of balance. Going to make a support bracket for the quill head also, as I've read they can flex a little under a decent cut.

anyway here's what I did to give you some ideas.....

Got my inverter coming in the post so will be getting it running this weekend hopefully...

View attachment 75393 View attachment 75394

whats that motor a newman half hp