Current wasted or leakage?

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  #1  
Old 10-14-14, 04:18 AM
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Current wasted or leakage?

I was measuring amps on an inducer motor. The amerage was a few milliamps lower on the neutral wire than the ungrounded wire and I thought that might be something like current being wasted if there is such a thing (similar to voltage drop) or maybe current leakage to ground?

In this case it was a motor that was rated at 2.3A. I was measuring about 2.0 on the black wire and about 1.9 on the neutral. Very miniscule, but it made me curious .
 
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Old 10-14-14, 04:43 AM
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There is no such thing as a current drop analogous to voltage drop. If you have 2.0 amps on the black wire then 2.0 amps are going the other way whether all in the neutral or some in the ground.

If you have that much leakage, then there is likely a problem in the motor that will get worse over time and quite quickly. Like a short between a winding and the core which will become a tiny overheating point.

A difference between 2.00 amps and 1.90 amps is way too much to be considered tolerable leakage That loss would be regarded as a fault current. (A fault is an unintended unwanted connection or bonding between two current carrying or grounded objects.) A difference between, say, 2.000 amps and 1.995 amps is probably leakage that is not practical to cure.

Or maybe your ammeter has a fairly large tolerance such as +- 6%, being sensiitive to nearby wires as well as the the wire between its jaws.
 

Last edited by AllanJ; 10-14-14 at 05:11 AM.
  #3  
Old 10-14-14, 07:27 AM
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I checked again this morning.

Clamped around the ungrounded black wire I was reading about 2.05 -2.10A
Clamped around the neutral white wire I was getting a few milliamps less like 1.95-2.0.
There was like .06 approx. or less fluctuating on the green wire ground. So I think that difference is on the ground.

The accuracy range on my meter says 3.0%+10 digits.

Should I be concerned about this?


addition:

I realized that placement of the clamp is effecting the readings to. The readings change as I go closer or farther from the motor. If I test the leads at the same distance from the motor on each conductor the values fall in line with each other. I think I may have been testing the leads at different points with the unbalanced current.

Does placement play a role?
 

Last edited by mummy; 10-14-14 at 08:04 AM.
  #4  
Old 10-14-14, 08:09 AM
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Sure.... placement has something to do with it. The current flowing thru the wire is creating a magnetic field that your amprobe is measuring. As you get closer to the motor the magnetic field from the motor affects your readings.
 
  #5  
Old 10-14-14, 11:32 AM
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OK, so to confirm, the correct way to use an amprobe in this case is to measure the conductors at the same distance (or adjacent to each other). And measuring at different lengths will give an unbalanced reading.
 
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Old 10-14-14, 12:55 PM
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Different lengths or locations is not the actual issue. It's what's in the area.... like a transformer or motor.
 
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Old 10-14-14, 01:07 PM
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closer to a motor will cause incorrect reading. OK, PJ why is that? For the sake of understanding?
 
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Old 10-14-14, 01:19 PM
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Anything that generates a magnetic field will cause erroneous measurements.
 
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