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.
P.S. 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 nothing..
leave it run for longer and see how hot it gets..
Does it have a starter relay or cap that is defective?
Mark
Hi, Are you reading peak current or average current draw? When motor starts there is a surge of current.
Is it possible for you to check the current draw with another kind of meter, say a conventional clamp-on ammeter?
That 17 amps being drawn when unloaded sure doesn't sound correct to me.
Jeff
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.
Hi, 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 inductive.
They do read true watts, and are fairly accurate. They also tell you what the power factor is. So, all in all, pretty neat little gizmo.
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.
Hi, Then the motor is sick.
It has a starter relay that disengages properly. The start cap is new.
Average draw after the motor reaches speed.
Good idea. I'll dig out my clamp-on. Thanks for reminding me.
*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.
Is it brand new, or been around a while? Might be the berrings are dry, and it's under a bit of a load, trying to spin. Give it a couple drops of ND-30 oil in the berrings, and see if that works better.
Someone else also mentioned using clamp on ammeter. That might give different number.
You may be on to something - that, coupled with the limitation of the Kill-A-Watt to 15 amps, leads me to go ahead and perform the "Smoke Test."
Are you misreading 18 as 13?
The table in the NEC gives 16 amps for an "average" 1 HP 120V motor. That, along with the nameplate value of 13A is for a fully loaded motor. Are you operating with a mechanical load?
Watts might also be of interest. A 1 1/8 HP mechanical load is 840 watts. Then there are losses that add. I never looked at the watts of an unloaded motor. Should be far less - most of the current is reactive.
That seems to be way high for a motor that is not under any load. Either a faulty meter or the motor is bad.
The strait answer, is that it's a path from Alaska to Russia.
It could also be plain, needle, or sleeve. (Sounds like the start of a joke. A man has a plain, needle and sleeve. His boss asks him to make a berring...)
I read that as "Palin needles the sleeze." Must be projecting....
Could well be.
But, also note that the Kill-a-watt can get a little squirly if you exceeed it's max rated current.
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