What's that Lassie? You say that Bruce L. Bergman fell down the old
rec.crafts.metalworking mine and will die if we don't mount a rescue
by Tue, 27 Jan 2009 23:31:55 -0800:

(dan) wrote:

I think I will just assume full nameplate amps when loaded and
multiply by the duty cycle.

BTW, I had been wrong on the voltage all along. It's being fed from
one of the 460V panels.


And if yours is a constant run unloader system (usually used on big
industrial piston compressors, and most screw type units) you can pop
on a Clamp Amp to estimate the current under load versus the current
when idling to get a discount factor for that.

It is, and I did. 15A loaded 10A un-loaded.

The ammeter doesn't care about 230V vs 460V, but your fingers sure
do, so be REAL Careful with the covers open and the unit energized.
460V will knock your ass across the room if it gets half a chance.

Hell, 220V scares me so much, I've never been bit by it. 110V stings
plenty, thank you. If I had known it was 460v I might not have
bothered taking a reading. But there was plenty of room in the
control panel and the line in wires were easy to get the clamp around.

I'd suspect that the current will drop to about 50% of Nameplate FLA
when unloaded, but even lower is quite possible.

I thought so too. When it wasn't, I thought I should ask here.

You aren't going to be able to tell true power draw without a way to
read power factor (inductive lag, capacitive lead), and the metering
gear to find that out is going to be real spendy. Guesstimate.

Yep. That seems to be the consensus. I'm going to estimate high by
assuming nameplate FLA. That and the duty cycle should be close
enough.

Thanks.

--

Dan H.