Phase Balance Questions?

I just tried to post this and it did not go on. Not sure why, but I will do it again.
Try to keep your answers in laymans terms as I am not completely Electrically Literate.
I have my 5hp Phase-A-Matic all wired up and running. My setup consists of a 3ph fused disconnect that starts the converter. The converter feeds the generated leg thru the center pole of the disconnect and into a 3ph panel box where a breaker feeds my machine. I did it this way so I can add more machines easily.
When I start the converter it is noisy, but mostly vibration rattling the florescent fixtures (I mounted the converter in the attic so I wouldn't hear it ha ha). When I put a load on, it seems to quiet right down instantly, so not a big problem as I am too cheap to leave it running if not absolutely necessary.

When the lathe runs for a little while, it starts to pick up a kind of resonating howling sound that gets louders and louder until you start the spindle, at which point it quiets right down again.
This does not sound or feel mechanical at all, no vibration or metalic ring to it, so I poked around with the tester a little bit and here are my results: (Bear in mind, T1 and T2 are my grid feed legs and T3 is my generated leg)
T1-T2=244VAC
T2-T3=277VAC
T1-T3=266VAC
T1-Neutral=120VAC
T2-Neutral=120VAC
T3-Neutral=243VAC
Everything is running at 60hz.
All these measurements are No-Load. I didn't even think to test it under load, I can do that if necessary.
Are these results typical and is this power useable? I thought this "Store Bought" converter would be a "Plug and Play" deal. Do they normally need to be tweaked with resistors or something to ballance them out?
Does it seem possible that this noise would be power, or should I look for a mechanical problem in the lathe?
My lathe is a 1942 Monarch 12"CK if that is helpful.

"T1-Neutral=120VAC"

Correct, as this is a 120/240 residential or commercial/light industrial service.


"T2-Neutral=120VAC"

Same answer.


"T3-Neutral=243VAC"

Very high ... 17 percent high, when the goal is +/-10 percent (187.2 to 228.8).

However, this line-to-neutral voltage, while very high, can be misleading as the voltages of interest are line-to-line and not line-to-neutral as the machine does not use neutral.


"T1-T2=244VAC"

1.7 percent high, which is fine.


"T2-T3=277VAC"

13.5 percent high, which is still too high.


"T1-T3=266VAC"

9 percent high, which is OK.


As these are no load values, you really do need to provide some loaded values.

My guess is the T1-T3 value will go way, way down, close to T1-T2, and the T2-T3 value will go way down, closer to 256.


With a "packaged" solution, it is not too awfully productive to try to achieve balance as doing so by adding capacitors may make the unit not self-start.

I will test it with the lathe on and see if that generated leg comes down in line with the others.
If it does should I assume that nasty noise is something mechanical in my lathe, or can someone think of something else in the motor/electrical system?

i had the same problem at a friends house-shop. the problem was in the panels earth ground , as it did not have a separate ground and was run though the neutral leg. this was causing noise and weird stuff ,we ran a new earth ground just to the RPC from outside and fixed it .

Earth Ground

I have a separate Earth ground from my main panel into my 3ph panel and the Converter Frame is hooked to that, do you think that should be sufficient?
I was always told you should never have more than one point of Ground (earth) reference in your system. Anyone think along those lines, or should I look at putting in a ground rod just for the 3ph system?

Tested under Load

I finally tested my system under a load this weekend and that was the problem.
The Generated leg is a bit wild without a load, but once I had the Lathe motor running, everything evened out very nicely. All three legs were 238V from leg-leg.
Thanks for the advice and help.

Almost forgot. The noise that started this discussion seemed to go away after I used the lathe some. Maybe something in the motor from sitting in stoarage for a while before I got it.
Whatever the case, that old Monarch quieted down and now runs so nice and smooth it is a pleasure.
I'm very happy with it.