Rotary phase converter problem

[OFG]

I have a 240V rotary phase converter with a 15HP motor on it. It is about 30 years old, and I decided to shotgun the capacitors - 12 caps in parallel, each is a 50 mfd 377 volt cap. It was working when removed from service, but the caps were looking corroded and I wanted to work on it when I had time.
I put the new caps in, and it started / ran great.
Tried it again to check the motor bearings, still great. Coasted a long time, bearings sound fine.
My buddy decided to try it with a motor when I was not around, and paralleled a 3 HP 3PH motor right across the 3 motor leads.
When he turned on the breaker, it sounded like it was single phasing and would not spin.
I took off the 3 hp motor, and it still would not spin - sounds like the motor is single phasing.
I checked all the capacitors with an industrial capacitor tester, they are all good.
I unhooked all the capacitors and took the motor to a motor shop and put it on 3PH 230V, it started and ran great - very smooth, even current on each leg.
I put another set of known good capacitors on it and tried it on my original 245V 1PH supply - it still won't start - still sounds like it is single phasing.
I can't start spinning the motor with a rope, because the factory cut the shaft off and capped the shaft on both ends.
I am kind of stuck here - does anyone have a suggestion for what I can try next?
Thanks in advance -
Old Fat Guy

[Al_The_Man]

It sounds like your start circuit is not working? how is it started by start cap and PB and or PB & timer.
Al.

[OFG]

It has never had a separate starting circuit. No timers or start capacitors.
The capacitors are across T2 and the generated leg, and T1 and T2 have always been connected to a 2 pole switch on the single phase 240V supply.
I prefer the newer units with starting circuits, but this one has worked OK without one for the last 30 years.
I can't figure out what has changed.

[Al_The_Man]

I have never come across a RPC that did not have a start circuit, especially when you get up to 15hp?
In a simple application a PB would place a large value bi-polar Cap from one of the 240v 1ph lines to the artificially generated phase to start rotation.
This provides a high out of phase starting current in the third phase, similar to what is done in a split phase 1ph motor.
In your case, I would guess that in changing the caps, you omitted or changed the value of the start cap.
Al.

[OFG]

I will shoot you a picture if I can.
I have (12) run capacitors, all are 50mfd @ 370VAC and they are all parallel with each other across T2, which is AC line 2, and T3, which is the manufactured leg.
Noisy on startup on a good day.

Deep here in Farmland, we actually have phase generators with _no_ capacitors.
They use a single phase motor shaft connected to the three phase motor shaft, and power up the single phase motor first. After it comes up to speed, they throw power on the 3 phase motor. After it comes up to speed, they start adding the 3 phase loads. Can't be pretty (don't even want to see it on a scope!) but it runs the grain augers OK. I would not use it like that, but some of the old school guys do.

[Al_The_Man]

Apart from the starting situation it has probabally never been tuned.
Here is a typical set up. look at the FRW- files.
metalworking.com - /dropbox/_1998_retired_files/
Al