On Thu, 01 Dec 2005 14:46:57 -0800, Grant Erwin
wrote:

jim rozen wrote:
In article , Grant Erwin says...

I have a phase converter with a 7.5hp idler. I never envisioned having to run a
7.5hp load, but now I want to try it. This is a question for either someone
who's done it or for one of the pointyheads who abound on this NG. If I were to
first start my phase converter, THEN start e.g. a 3hp motor with no load, can I
then run a 7.5hp load motor fully? My thinking is that the 3hp motor would act
as an "idler booster". In this way my phase converter (I'm hoping) can be made
to act as though it had a 10hp idler.


Short answer, yes.

If properly tuned it might start it without the extra three in there.
This sort of depends on what kind of load you have.

I'm pretty sure I can *start* the thing (big abrasive cutoff saw) but what I
want to do is to source enough current so I can run the saw fully. I always
thought you could run one size down e.g. if you have a 7.5hp idler you can run a
5hp motor fully.

First things first is to see how well it starts on the 7.5hp idler.
If it starts fine then you'll be good for most of your work. Then if
for some reason you want to saw something heavy you can go turn your
lathe or whatever on and use it for the boost needed for the heavy
work.

I am considering adding some run caps to the idler booster unit, so when I
switch the unit off they will be out of the circuit. Only when the idler booster
is running would the extra run caps be apparent.

It's certainly the best way to do it but I wonder if it'll be
overkill here.

Wayne Cook
Shamrock, TX
http://members.dslextreme.com/users/waynecook/index.htm