Wiring up a 30HP rotary phase converter

[Oscar]

I don't have it yet, it's being shipped as we speak. I hope to have it next week. In light of this, I have started this thread since I've never seen one in person, nor wired it up. The unit is a 30HP from Southern Phase Converters in Texas. The unit is "new", but I bought it 2nd hand since I was able to save a few hundred.

In the meantime while it gets here, I wanted to talk about power input. To do that, I think we need to look at anticipated power consumption, which will be at most 36A (I1max) @ 230V while on 3-Φ (from the ►machine electrical spec sticker◄). By my calculations, that is equivalent to 14.4kW. The ►motor spec sheet◄ says 93.6 efficiency. So it would at most consume 15.4kW. Working backwards, that seems to indicate that it will pull 63A from the 240V 1-Φ supply side.

Do I have that correct thus far?

[Chad86tsi]

I come up with the same figures. I'd be worried about the inrush to start current that motor in the phase converter though, since it's rated for so much more than you'll be running it at. Does it have ratings for that?

[Oscar]

I didn't see such a rating on the spec sheet. Are you talking about the in-rush to initially get it up to speed when it is flipped on? Or something else?

[Willie B]

Highly unlikely you will feed it with 240 volts. If your voltage even occasionally falls far below, efficiency will change sharply. Lets factor 225 volts, 80% efficiency.

This is a motor, we size motor circuit conductors at 125%.

The reality is you bought a BIG phase converter.

Wait a minute! Three phase, 1 HP is about an amp at 600 volts. At 230 volts Full load current is about 80 amps.

I'd figure 80 amp output. X 80% efficiency. Effectively 100 amps for conversion purposes at 80% efficiency gives you rated output. roughly 100 amps (a bit less)

Full load of something close to 173 amps. Don't panic, you won't likely pull full load.

Keep in mind 1 HP at 100% efficiency is 746 watts. 30 HP X 746 is 22380 watts You won't power 30 HP at 746 watts per, There is some waste in the motor. 1000 watts is a conservative estimate, or 30,000 watts. At 230 volts that'd be 130 amps. But we factor Three phase at 1.73 so 75 amps output.

30,000 At 230 volt single phase is 130 Amps.

I would expect your converter is overrated. Regardless, you won't likely power 30 hp motors

I will be interested in the installation instructions. I have a 6 horsepower vacuum cleaner draws 12 amps single phase 120. 6 X 746 = 4476 watts. Actual draw is 1440 watts. Somebody is fibbing!

[Oscar]

Highly unlikely you will feed it with 240 volts.

You're right about this. It's actually 245V coming into the house. It is a very solid supply.




I know you want to cover a whole lot of ground as your mind races through the subject to give an all-inclusive lecture/lesson, but you haven't actually helped me. This will be specifically to power my TIG welder. The link to it's spec's I already listed. The motor spec I also linked, so a lot of the speculation you did could simply be avoided if you click the links. All your talk about full load means nothing. I only want to power the TIG welder. If you want to help, I'd certainly appreciate it. Please revisit my 1st post and comment specifically on my calculations, based on my criteria, not wild mental ramblings. Thank you.

[danielplace]

Oscar,
The 30 hp phase converter is good for 15 hp of load.

I would size the input at near full rating.

#1's from panel to the converter A and B single phase inputs and 100 amp breaker.

From A, B and C from converter panel to the idler you would use #8s.

Then from your A and B inputs and the C coming back from idler you feed your 3 phase panel with #4's.

>>>> NEVER use the A and B for the idler for anything else but converter panel to the idler ONLY.

If not using a panel to split up loads or set your self up for future then just run what your powering with only the size wire it requires. Be sure to provide proper over current protection as soon as you leave the phase converter. Smart to have some way to kill power at the machine too if the panel or disconnect is far from the phase converter.

[Oscar]

Oscar,
The 30 hp phase converter is good for 15 hp of load.

Well that's not good. I figured I could squeeze a lot more than 1/2 it's capacity! Isn't that typically more so for starting other motors, since they start a lot "harder"? So you're saying I would not be able to squeeze out all the amperage out of my welder with it??

[Willie B]

They are typically rated for single motor horsepower & multi motor. It might be rated at 30 hp cumulative, but 11 or 12 single. Do you have a 30 HP machine to power?

[scsmith42]

Oscar,
The 30 hp phase converter is good for 15 hp of load.

I would size the input at near full rating.

#1's from panel to the converter A and B single phase inputs and 100 amp breaker.

From A, B and C from converter panel to the idler you would use #8s.

Then from your A and B inputs and the C coming back from idler you feed your 3 phase panel with #4's.

>>>> NEVER use the A and B for the idler for anything else but converter panel to the idler ONLY.

If not using a panel to split up loads or set your self up for future then just run what your powering with only the size wire it requires. Be sure to provide proper over current protection as soon as you leave the phase converter. Smart to have some way to kill power at the machine too if the panel or disconnect is far from the phase converter.

Daniel, according to the tag on his RPC (shown in post #43), the FLA is 71 at 230VAC. Wouldn't he need to run #4 from his RPC panel to the idler, instead of #8? Even with 90 degree C insulation, a #8 is only rated at 55A.

[danielplace]

Daniel, according to the tag on his RPC (shown in post #43), the FLA is 71 at 230VAC. Wouldn't he need to run #4 from his RPC panel to the idler, instead of #8? Even with 90 degree C insulation, a #8 is only rated at 55A.

You only need those amps on the single phase feeding the converter panel.

Rotary phase converters are typical. Here are some wire size charts for similar units. Check the 30 hp line. His could be wired with similar sizes I believe and work as designed.

Not any phase converter guru. Wired several over the years in smaller wood working shops.

It does seem odd that the idler wouldn't need at least the same as the C phase it is feeding out to your 3 phase on.
That is how they are designed and work though. I think the two single phases are actually bucking to the created phase so they cancel each other out and only the unbalanced returns on the C phase to the idler. For this reason the idler wiring can be smaller. I wouldn't take it to the bank that is how it is exactly but of course that leg doesn't have same voltage as others to ground so it is not taking the load of the others either maybe.

He should have some similar specifications from the manufacturer of his exact unit.

[Robb M.]

test post

[Oscar]

Now it works, thanks Robb!