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Posted by Ralph Mowery on October 30, 2009, 12:06 pm
> Tony Hwang wrote:
>> HeyBub wrote:
>>> 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...
>> Hi,
>> Are you reading peak current or average current draw? When motor
>> starts there is a surge of current.
> Average draw after the motor reaches speed.
That seems to be way high for a motor that is not under any load. Either a
faulty meter or the motor is bad.
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Posted by jeff_wisnia on October 29, 2009, 10:21 pm
HeyBub wrote:
> 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...
>
>
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
--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10e12 furlongs per fortnight.
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Posted by Existential Angst on October 29, 2009, 10:44 pm
> HeyBub wrote:
>> 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...
> 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.
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.
--
EA
> Jeff
> --
> Jeffry Wisnia
> (W1BSV + Brass Rat '57 EE)
> The speed of light is 1.8*10e12 furlongs per fortnight.
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Posted by Tony Hwang on October 29, 2009, 11:07 pm
Existential Angst wrote:
>> HeyBub wrote:
>>> 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...
>> 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.
> 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.
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Posted by Zardo Zapp on October 30, 2009, 12:02 am
>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.
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.
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