Would like someone with the expertise to help clarify reading a load on parallel feeds. We have 4sets of 500mcm pulling max of 169 amps on one wire of one set: Question: Do you add the reading of each wire of the set to get the total load on that phase, or is the total load the reading of one conductor. Each wire in the set is reading close to the same, our digital clamp meter will go around two of the wires, and we still read the same as one. I have been told by an "expert" that you add the current on each wire for the total on that set of phase conductors. Thanks for your help. Ken
Measurement of total amps in parrallel runs
- Thread starter ktever
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If you have 4 sets, you should be reading about the same on all of the 4 conductors. If true, then the reading on 1 500 x 4 = total current on that phase. Or you can take a reading on each of 4 conductors and add them together for the total on that phase.ktever said:
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- Location
- Lockport, IL
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- Semi-Retired Electrical Engineer
You add all four to get the total. In your case, you have four times 169, or 676 amps.ktever said:
Now you have me confused. Are you saying,ktever said:
(1) You put the clamp meter around a Phase A conductor from one set and a Phase B conductor from the same set, or
(2) You put the clamp meter around a Phase A conductor from one set and a Phase A conductor from another set?
If you meant (1), you should get the same reading. If you meant (2), you should get twice the reading.
winnie
Senior Member
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- Springfield, MA, USA
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- Electric motor research
For clarification:
You have 4 sets of 500 mcm conductors.
By a 'set' you mean a _single_ conductor for each phase (plus the neutral if applicable). So a set might have a single phase A conductor, a single phase B conductor, a single phase C conductor, and a single neutral conductor.
When you put your clamp meter around a _single_ phase A conductor, you measure 169A. All of the 'phase A' conductors are pretty much equal.
When you put your clamp around _two_ conductors, you still measure 169A. You believe that the _two_ conductors that you are measuring at the same time are both 'phase A' conductors.
Do I have the above correct?
1) The _total_ phase A current is simply the sum of the current flowing on each of the phase A conductors. Thus _if_ the 169A measurement is a true value, then you should see a total of 776A on all four conductors of phase A, and 338A on any pair of conductors.
2) If the system is balanced across the phases, then you would see a similar current flowing on each of the other phase conductors. An interesting fact: if you have 'X' amps flowing on a phase A conductor, and 'X' amps also flowing on a phase B conductor, and you measure both conductors together in your clamp, you will still read 'X' amps. This is because the phase A current is not in phase with the phase B current.
Given the information that you've provided, I would suspect a measurement error. Here are the possibilities that come to mind:
1) Perhaps the meter is 'maxing out' at 169A, and the real values are higher. If you have 180A on one conductor, and 355A on a pair of conductors, but the meter is maxed out, then you will read 169A in both cases.
2) Perhaps your phase identification is wrong, and that while you believe you are measuring two phase A conductors, you are actually metering across different phases.
It is also possible that you have correct measurements of the current flowing in the conductors, but that the process of measurement is changing the current flow.
1) Perhaps one of the conductors has a bad termination or a break. When you move the conductor to make the measurement of two conductors at the same time, you interrupt the current flow in that conductor.
2) Perhaps the meter itself introduces enough impedance that it changes the current flow distribution. While you are not directly introducing the meter into the circuit, it is magnetically coupled, which means a slight additional impedance on that branch of the circuit. (I would consider this very unlikely with any sort of normal clamp meter, but I'm throwing it out there as a reminder that the act of measuring something changes it, if only slightly.)
-Jon
You have 4 sets of 500 mcm conductors.
By a 'set' you mean a _single_ conductor for each phase (plus the neutral if applicable). So a set might have a single phase A conductor, a single phase B conductor, a single phase C conductor, and a single neutral conductor.
When you put your clamp meter around a _single_ phase A conductor, you measure 169A. All of the 'phase A' conductors are pretty much equal.
When you put your clamp around _two_ conductors, you still measure 169A. You believe that the _two_ conductors that you are measuring at the same time are both 'phase A' conductors.
Do I have the above correct?
1) The _total_ phase A current is simply the sum of the current flowing on each of the phase A conductors. Thus _if_ the 169A measurement is a true value, then you should see a total of 776A on all four conductors of phase A, and 338A on any pair of conductors.
2) If the system is balanced across the phases, then you would see a similar current flowing on each of the other phase conductors. An interesting fact: if you have 'X' amps flowing on a phase A conductor, and 'X' amps also flowing on a phase B conductor, and you measure both conductors together in your clamp, you will still read 'X' amps. This is because the phase A current is not in phase with the phase B current.
Given the information that you've provided, I would suspect a measurement error. Here are the possibilities that come to mind:
1) Perhaps the meter is 'maxing out' at 169A, and the real values are higher. If you have 180A on one conductor, and 355A on a pair of conductors, but the meter is maxed out, then you will read 169A in both cases.
2) Perhaps your phase identification is wrong, and that while you believe you are measuring two phase A conductors, you are actually metering across different phases.
It is also possible that you have correct measurements of the current flowing in the conductors, but that the process of measurement is changing the current flow.
1) Perhaps one of the conductors has a bad termination or a break. When you move the conductor to make the measurement of two conductors at the same time, you interrupt the current flow in that conductor.
2) Perhaps the meter itself introduces enough impedance that it changes the current flow distribution. While you are not directly introducing the meter into the circuit, it is magnetically coupled, which means a slight additional impedance on that branch of the circuit. (I would consider this very unlikely with any sort of normal clamp meter, but I'm throwing it out there as a reminder that the act of measuring something changes it, if only slightly.)
-Jon
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