phase converter

[cubdriver55]

I want to run a 25 HP 3 phase motor on a band saw mill. I have a 400 amp 220 single phase service. I have been told I need a 50 HP rotary converter. I have a temco 30 HP converter now. Can I add another converter to this 30 hp converter I have and if so what kind of soft switch is needed to start these converters? Thanks  Steve

[r.man]

Cubdriver, are you running the 30 hp converter now or have you just acquired it? I expect that you are going to have trouble getting an accurate answer to your question about stacking converters. I do expect that you will get lots of answers but whether they are right is another thing. What kind of price difference are you talking about with upgrading compared to adding and are you going to do the work yourself. My first inclination would be to try to sell or trade the 30 for a 50 or larger used unit if I could do it for very little cost. If the 50 was prohibitively expensive I think I would stack but I have very little experience with rotary converters. I have only seen two in person and only wired one. From what I know of three phase, capacitors and motors I think it could be done safely but I am not sure. If I am wrong I don't think the explosion would be large but it would probably be fairly expensive in equipment and fuses. If it were me and I had talked to someone I trusted and they assured me that they had done it safely I would have no qualms about doing it. How is that for a bit of a weasley answer. I will try to do a bit of research and see if I can come off the fence one way or the other. Let us know what you find out because I think this is something that would apply to a fair number of members. 

[J_T]

Don't know the answer but i do know i am running a 20hp 3ph motor with a shop built  25hp converter . Also a Brewco lowride unscrambler that has two motors on it  ??? Also a hyd power pack and a chop saw. Have ran a 15hp for a while from a ten horse converter as that was all i had and needed to run bad . I let my 20hp get up to speed before engaging the drive as the coils on my starter tend to heat starting under a load . I use a 110v light switch to trip the coil on the starter .

Am running a shop built re saw with hyd power feed it runs lots of hours a day when i feel like working . We designed it for cutting long cants one right behind the other .

I am on my own transformer and it is a new one . Their old one had a small problem : I blew it  ;D  

[r.man]

Cubdriver, Temco's site says that you can stack Temco converters as long as they are phased properly and the input wiring is sized properly for the overall load. I like to learn something new every day. I can now go to bed happy. I do like J-T's idea of trying to start your saw with the existing converter. Now that I think about it more a rotary phase converter improves with three phase load so if you had a smaller motor that the converter would start easily, say a 10 hp and then started the 25 it would probably help.

[J_T]

You can hook one motor to the next an so on and build converter size too. But on the wild leg i think mine is hitting 180 to 190 volts . Your 110 volt lines can be a pass threw or by pass lines . Main need really is keeping the voltage up on the wild leg the other two are pretty well fixed .  : Clear as mud  ???

If i was on my own transformer i would run it as is . If not i would design a soft start pony on my mill motor  most anything will bring it to speed with no load .

Got a guy wanting me to design  him a converter to run fans but must be able to switch to generator and restart in a power outage then switch back on return of grid power .

[J_T]

R-man  just noticed you are in Canada i got some motors from that part of the world that have unusual voltage for this area . Some factory's run them but not as common as 460. Haven't looked at them in a while but think they are 500v 3ph . Been aiming to experiment and check the volts using as a converter on the high leg . ???

[BandsawWarrior]

I run a 40hp phase converter from pheonix phase converters.  Yes you can stack them which is better anyways because it's easier to start two smaller idler motors than one large one. 

Our 40hp idler motor starts no problem off 200 amp service.  You just have to make sure you have the proper wire size.  Our idler motor doesn't have any type of soft start and it fires up no problem. 

I'd get as big as you can afford because you'll always add stuff down the road....we started with one machine running off the phase converter and now I need to get 3 more hooked up!

[r.man]

J-T, I am in central Ontario. Canadian three phase is 208 volts, 120 to neutral or 575 volts, 347 to neutral. 208 gives you the advantage of three phase without having to transformer for convenience power. 575 allows for smaller wire size but you must have a transformer to power a convenience panel. It is not unheard of for companies to transformer to american three phase voltage for a specific machine but in general motor changes are the way to go for the long term. Wired a pallet plant a few years ago that came from Baker. Just had to specify 575 motors and except for them forgetting and sending two 460 volt freak drives it was painless. Gotta love the global economy.

[J_T]

Yep 575 that is it  : On a hyd. power pack about 20hp  :(

[cubdriver55]

Thanks for the help. I have not used the converter or the mill yet.I am going to hook it up and try it with the 30 and see if it will start. I have a circle mill that I have not run for years. I allways wanted a band mill so I decided to get one and try it. The Timber Harvester I have is all hydrolic so I hope that does not make it harder to start. The mill I have was purchased in 2002 and the owner passed away without ever hooking it up so the only time on it is from thr test run at the factory, so I am sure it will be hard to start the first time since it sat for so long. Thanks Steve

[uncle kenn]

Is there anyone out there that can tell me what size phase converter i would need to run a 50hp and a 40hp ele moter at the same time? Also looking for someone to build one foe me.  any help will be appreciated, UK

[J_T]

I would build it my self using a 50hp then if any doubt go to the 40 threw it to my other 50 . Or just use a fifty big thing is a good power source for this operation with its own transformer from the grid  : If no computers are involved this will work have done it my self . Don't know about with computer set works but may pull another dedicated line to run them .  ???

Also standard disclaimer apply s  . This info is worth just what i charge for it nothing  ;D ;D

[r.man]

UK, to put it plainly do not undersize your wire and breaker/fuse to the converter. Oversizing will not hurt and may make the difference between this working or not. There are lots of times that undersizing a wire does not hurt but this is not one of them.

[J_T]

UK, to put it plainly do not undersize your wire and breaker/fuse to the converter. Oversizing will not hurt and may make the difference between this working or not. There are lots of times that undersizing a wire does not hurt but this is not one of them.

Oops you are right on treat the wire size like it was single phase plus length . The high leg is the only leg not pulling a bunch of amps . :D

[uncle kenn]

I have found a3 phase converter that has a label that gives themax hp as 75, does that mean it would run my 30 hp, 20 hp and 5 hp at the same time? uk

[Larry]

Your asking questions only an smart electrician can answer with all the facts.  Some motors are just plain easier to start than other motors.  Clutched motors are easier to start than motors under heavy load.

Call the guy that made your phase converter and ask him.  If that's not possible see if you can try out the phase converter before buying.  My guess is that it will work...but like J_T my advice is worth what ya paid for it.

[J_T]

I have found a3 phase converter that has a label that gives themax hp as 75, does that mean it would run my 30 hp, 20 hp and 5 hp at the same time? uk

Simple answer yes . 8) 8)

[r.man]

I agree with J-T if it is a rotary converter. If it a static then I would vote maybe and second Larry's advice of asking the manufacturer first or someone experienced second.