I am measuring after the breaker.? Swapping lines out of the breaker does not change the measurement so the issue is before the breaker.? When I first measured currents Leg “B” was low.? It was low for the first month or so.? Measured all three phase motors individually this way and all were always low on Leg “B”.? Some days Leg “B” was low by 20%, one day 49% low.? The even that caused me to measure the currents was a new ABB VFD that would fault.? First week spent diagnosing with ABB Techs.? This is when we did things like moving wires and lots of measurement.? It took another week to get the utility to send out a tech.? They send a “troubleshooting” tech who came with the same Fluke Multimeter and he measured voltages and said all good.? The first tech clearly new nothing about 3 phase power.? Pushed the utility and they sent a second tech, same thing.? Escalated and they sent a third “troubleshooting” tech who at least new about 3 phase power.? He couldn’t do more as they don’t issue these techs more than a multimeter.? But he was able to issue a ticket for a “power quality” tech to come out with a power quality meter.? Then it took nearly 2 more weeks to get him out.? During that time I measured currents nearly every day and Leg “B” was low 20-40% every day in that time fame.

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I finally got a date and time for the power quality tech to come out and the night before I went out and measured and oddly Leg “B” was no longer low on any machine.? I measure every day and the currents are never very close to each other.? One would expect Legs “A” and “B” to measure the same and leg “C” would vary some.? But now I see Leg “B:” as always higher than Leg “A”.

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Nothing has changed in my shop.? I’ve done the measurements with all single phase loads off and each motor isolated so the motor I am measuring is the only load.

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Based on the power quality meter the voltage relationships are perfectly 120 degrees apart.? Moving wires on the breaker (different windings on leg B) does not change the data.? If the voltages are correct and the phasing of the voltage are correct, and changing the motor wiring does not change the current measurement, all that must be left is inductance or capacitance differences between legs from the utility??

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