3phase & Re: 50uF + suplus motor run caps sources???

Good point!
In older tube guitar amps , The HV plate supply sometimes
has 2 caps in series for higher voltage rating.
These caps would have a high value
resistor across each. This (divider) seems to both help
center the voltage sharing and discharge them at powerdown.
But thats was a DC condition.

The AC condition is as you say, since caps can act also as
frequency controlled impedences Rc = 1/wC. They could easily be
unbalanced due to variances.

I havn't tried hanging caps off of powerlines before, so
overlooked that. I'm going to bite the bullet and get the
3 80uF/375 volt caps from grainger($29ea). At least I'll know
they are new. I have a potential relay so I can use the cheaper
electrolytic startcaps at startup. (10hp idler)

Thanks for the sanity checks,
Lee