Rotary Phase Converter

ctmillworks · Dec 13, 2008

Need help picked one up today no hp or who made it no paper work how do I find
out what the hp is or how much I can run on it at one time I do have a SB lathe
and a Surface Grinder all 3-Phase " HELP ME "

JST · Dec 13, 2008

ctmillworks said:
Need help picked one up today no hp or who made it no paper work how do I find
out what the hp is or how much I can run on it at one time I do have a SB lathe
and a Surface Grinder all 3-Phase " HELP ME "

Well, no information means just that. If you can't find out anything from it and you can SEE it, we sure can't.

Look it over and see if there is any data plate giving any numbers and so forth. Look INSIDE the connection box also.

If there truly is nothing, you have a pig -in-a-poke, and I wouldn't want to speculate.

Even size isn't much help, I have a 1 HP motor that is small and relatively lightweight, and another one that is huge and weighs almost 100 lb.

precisionworks · Dec 14, 2008

Your RPC should have three wires coming out of the idler motor, or three wires coming out of a connection box. The wires should be labeled T1 T2 T3 like the diagram above. Connect T1 & T2 to your 240v single phase supply L1 & L2, the RPC idler motor should spin up quickly to full speed. Connect T1 T2 T3 to the lathe & switch it on, it should quickly come up to speed. If that works, connect the surface grinder.

Either it will work or it won't. If it works, be happy. If it doesn't, it may be difficult to figure out why not.

Barry Milton

ToughTool · Dec 14, 2008

Do you have any means to measure AC currents? HP ratings can be approximated from measurements. Can you take a photo and post it? Joe

johnoder · Dec 14, 2008

" HELP ME "

It is amazing to me how you guys punish yourselves. You are trying to learn a little about the subject and you do something like this to yourself.

Instead of scratching your head with this, why not get any old three phase motor that you know runs on 240 three phase and put it to work.

It needs to be a little bigger in HP than the biggest HP motor you want to start.

It will be your IDLER

It has three legs. You put 240 single phase (which has two hots) to two of them.

You have a switch or circuit breaker to do that

You start it someway - it will not start itself. Spinning it up with a rope before hitting it with the power works. There are of course fancier ways to start it, but don't confuse yourself just now

When it is running, the three legs are all hot. You feed this three hots to the machine three phase motors with safety switches/disconnects so it is safe.

They like it and start right up. The home made three phase isn't balanced yet, but that can come later. The silly three phase motors won't seem to care. They will just run. If you start the idler backwards, everything in the shop will run backwards - so pick a direction to spin it and keep to that direction.

Plenty of help here if you ask questions that can be answered.

John Oder

Ox · Dec 14, 2008

johnoder said:
It is amazing to me how you guys punish yourselves. You are trying to learn a little about the subject and you do something like this to yourself.

Instead of scratching your head with this, why not get any old three phase motor that you know runs on 240 three phase and put it to work.

It needs to be a little bigger in HP than the biggest HP motor you want to start.

It will be your IDLER

It has three legs. You put 240 single phase (which has two hots) to two of them.

You have a switch or circuit breaker to do that

You start it someway - it will not start itself. Spinning it up with a rope before hitting it with the power works. There are of course fancier ways to start it, but don't confuse yourself just now

When it is running, the three legs are all hot. You feed this three hots to the machine three phase motors with safety switches/disconnects so it is safe.

They like it and start right up. The home made three phase isn't balanced yet, but that can come later. The silly three phase motors won't seem to care. They will just run. If you start the idler backwards, everything in the shop will run backwards - so pick a direction to spin it and keep to that direction.

Plenty of help here if you ask questions that can be answered.

John Oder

What he said ^^^^^

I will add tho that:

A) A 1725 rpm motor is a LOT easier to git started than a 3450! :eek:

B) These days I just use a 3ph fusable disconnect. Hook your two hots to the top and the three from the converter to the bottom. You can now throw another set of lines in the bottom lugs to scurry the 3ph power off to wherever you want it.

C) I usta just leave a pulley on the motor and git rolling by kicking it over by foot. But on that 3450 sucker - you need a faster approach. A 110V motor with a belt werks fine. Keeping belt tension with your hoof (actually on the motor - not the spinning belt) when you throw the disconnect switch and watch the belt go scootin acrost the shop. LOL! (May not want to have your unit aimed out the door as you may hafta go chasin a belt out into traffis if your that close to a rd. :nutter:

----------

Think Snow Eh!
Ox

ctmillworks · Dec 16, 2008

here it is

JST · Dec 16, 2008

WEll, it appears to be a possible 'shop made" unit. Could be a "real product" of course, but no label............

It looks like it has a centrifugal (or other type?) switch to disconnect the start capacitor, which is the black one. The other one is a run-type capacitor, used to balance phases.

Red wire should be the "manufactured phase. It appears that the capacitors and switch are connected between the black and red wires.

So the incoming 230V would (after going thru switch and motor starter) go to terminals having black and blue wires. Unit should start up when power is applied, and automatically disconnect its start capacitor.

Size of motor looks generally "'1 HP size", possibly bigger, it's a bit hard to judge. the shaft size seems larger. The start cap value would go well with about a 1HP or so. Likely for a 1HP load or so.

Might take a look and see if you have a green wire from that green screw on the socket.... I can't tell if it has one, and there is no obvious spot for one in the box.

viper · Dec 16, 2008

You can certainly slim your possibilities by measuring all the dims of your motor and comparing to NEMA motor charts. There are probably only a few motor sizes that fit your dims including shaft specs. I would also "guess" by the panel hardware that it is homemade though I do like how the shaft is secured for protection. May or may not be a versatile option for some though.

It does not seem balanced very well with only one run cap. I would like to look at the voltages once running. Should probably tune that one a bit.

Ultimately, apply it to your load and watch the voltages under load. that will tell you if it will work for your application or not. I would take a close look at the wire sizes in the box to tell what kind of single phase wiring and breaker to use.

Remember that single phase amps/1.73 = 3ph amps

precisionworks · Dec 16, 2008

looks like it has a centrifugal (or other type?) switch to disconnect the start capacitor

That's exactly how it looks to me. I've never seen that on a three phase motor, only on single phase capacitor start units where the switch is located just ahead of the rear bearing. But it should work as long as the cap is correctly sized.

peterh5322 · Dec 16, 2008

Many three-phase motors are made on the same frame that a single-phase motor of smaller capacity is also made.

Perhaps it is possible to retrofit a single-phase centrifugal switch to a three-phase motor?

One 5 HP three-phase motor I have has the end bell already drilled and tapped for a centrifugal switch.

But, a potential relay is really a better solution, particularly as it has a fixed cost up to 5 HP, and a slightly higher cost above 5 HP.

chuckey · Dec 16, 2008

I say chaps, whats the gizmo mounted under the top centre of the box. On the top, it looks like a black knob with a blue semi-circle in it. I can make out "twist lock" on it but nothing else. From inside its a grey/white blob with two white wire going to it, both coming from the motor, black and red wires.
Frank

peterh5322 · Dec 16, 2008

That receptacle definitely states "Hubbell Twist-Lock" on it.

ctmillworks · Dec 22, 2008

Thanks for the help one thing I forgot was shaft size is 1 1/8 OD and no ground wire if this help
that is a 20 amp twist lock

JST · Dec 23, 2008

peterh5322 said:
That receptacle definitely states "Hubbell Twist-Lock" on it.

That type outlet probably a bit less common in Wensleydale than here...........

But he might think it IS a bit "cheezey"................ (compared to UK equipment)

I've never to my knowledge seen a UK 3phase plug, although I've seen a lot of the home-type single-phase ones..... as big as an electric shaver, with prongs like busbars..... I dunno what a 3 phase "industrial" UK plug would be like, might need a crane to pick it up.

precisionworks · Dec 23, 2008

shaft size is 1 1/8 OD

That is useful information, because it means that the NEMA frame size is either 182T or 184T. That means the motor is probably no larger than 7.5 hp.

I have a 1 HP motor that is small and relatively lightweight, and another one that is huge and weighs almost 100 lb.

That's the problem, because motors as small as 2 hp often use a 182T frame. Best SWAG is that your converter is somewhere between 2 hp & 7.5 hp. The only way to know if it's going to work is to try it.

ctmillworks · Dec 28, 2008

Phase Converter

precisionworks said:
That is useful information, because it means that the NEMA frame size is either 182T or 184T. That means the motor is probably no larger than 7.5 hp.

That's the problem, because motors as small as 2 hp often use a 182T frame. Best SWAG is that your converter is somewhere between 2 hp & 7.5 hp. The only way to know if it's going to work is to try it.

Hey thanks for the help mybe after the 1st of the year I will put it to work

ctmillworks · Jan 8, 2009

Phase Converter

Hay moved the shop around one more time and hooked up the Phase Converter
works fine I have it running my surface grinder with two motors on it 2 hp & 3 hp
so fare so good I will post photos later and Thanks for your replyes A Big help

PixMan · Jan 8, 2009

My dad & I got lucky, I guess. He found an old, but working 15HP 3-phase motor. We first hooked it up as shown in the above diagram, using a rope starter method.

I splurged for his B-day and got him a capacitor/starter box from a good Ebay vendor, and life is now simple, sweet, and SAFE. Lots of available power too! He can run his Victor 1640B lathe pretty hard and you never even hear it moan.

Rotary Phase Converter

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