I have a 115v, 1 1/8 HP motor with a faceplate rating of 13 Amps. It
actually draws 17 Amps (according to the Kill-A-Watt) with no load.
Does the difference mean anything important?
Thanks in advance for any advice.
I haven't run the motor for more than a couple of minutes...
could mean some shorted turns or binding bearings, (but you should be
able to feel that by turning the rotor by hand) or it could mean
leave it run for longer and see how hot it gets..
Does it have a starter relay or cap that is defective?
Should proly be 3 amps unloaded. 1 1/8 hp rating is kinda odd, eh?
I just bought a killawatt. I'll fool around some in the next cupla days.
I'm curious as to how it handles power factors.
If it is just calc'ing amps x volts, it's not really reading true watts.
Someone here once posted on how Con Ed type watt-meters work, in some
detail, most of which ran over my head, but I'd like to take another look at
that post, if someone has it marked. It was complicated enough (using some
kind of hysteresis saturation of metal or sumpn, ie, intrinsically
mechanical) that I wonder how a solidstate device can duplicate this. I
guess if it calc'd the voltage wave form and the current waveform sep'ly,
like on an oscilloscope, and determined the phase angle, it could be done
electronically, but I'll find out by comparing with a clamp-on meter.
That is easy if voltage leadning current vice versa, measuring phase
angle. Cosine Phi is power factor, right? Cosine 0 degree is 1 where
V and A is in phase which never happens in real world since most load is
Yes, I've compared them to reading from my Fluke 87 and they agree
nicely. The Kill-a-Watt is a very handy and economical gadget. They are
particularly handy when used with a Honda EU2000i generator camping.
Not necessarily. Some type of motors still draw lot of current with
little or no load. What changes is the power factor. They aren't
using much power because the current isn't in phase with the voltage.
In other words, they look like a big inductor rather than a resistor.
The power company hates these types of loads because there are still
losses (heat) in their lines due to the high current going through
imperfect wires, but the customer isn't paying much due to their meter
not showing much real power being used.
*With one horsepower equaling 746 watts even the nameplate rating sounds a
little high. If it is still high with your ammeter you could have a bad
bearing, but you should be able to hear that.
Let us know what you find.
The faceplate reads a clear "13.5 Amps."
Both the Kill-A-Watt (reluctantly) and a clamp-on ammeter show about 18-18.6
amps being drawn.
Interestingly, the clamp-on shows 18.5 amps on one wire and 16 on the other.
The difference must be in heat. Or condensation.
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