Greetings all,

Haven't had time to stop in much recently, but I'm finally getting my
new shop
close to ready to power up, and in wiring up the phase converter for
the Rivett,
I've hit a parts question for which I can't seem to find a ready
answer:

How much AC current would be reasonable to switch, using
a 40A DC-rated contactor (not a DC coil - magnetically
extinguished DC-rated contacts).

My intuition is to believe that it can safely carry (break) a heck of
a lot more AC current than DC current. I believe that I saw,
somewhere,
once upon a time, a derating rule of thumb, for using AC-rated
contacts
with DC. Even if my memory is playing tricks on me, it stands to
reason
that if it can break and extinguish a 40A DC arc safely, then the
self-extinguishing zero crossings of AC should make it good for a bit
more than that.

The question comes up because the spare contactor from the parts box
that
fits the right hole in the converter box, for the start-cap relay,
happens to be
a Josyln Clark "definite purpose" 40A DC contactor. I'm hoping that
split
between its two NO contacts, I can switch enough start capacitance for
my 15Hp idler.


I suppose that raises another question - should I split the start-cap
bank
into two banks, and run one off of each NO contact, or connect them
all
up as a single bank, and just treat the pair of contacts as parallel
wiring?

If I parallel just the contacts, the trailing contact will be
effectively
breaking the entire starting current by itself - this seems to argue
for
splitting it into two banks, one on each contact?


Here's hoping this beast doesn't let the smoke out when fired up!
Will Ray