Mick:
Do you have access to a dual trace oscilloscope? That is how I check phase
angle.
William
At 09:45 PM 4/7/2011, you wrote:
Hello, Mechanics~
I went to a distant "off grid" jobsite where my client has an
inverter/charger system set up for 120/240 60 hz system architecture.
While investigating some screwy charge behavior I clipped my "pretty good"
Extech clamp meter around the various AC wires from the generator, with
the meter set for frequency display.
The two hots looked good around 60 hz but the neutral was showing wacky
frequency numbers much higher...and about double. The ground also showed
similar wacky frequency numbers so I think there is a ground fault but my
greater worry at present is the approximately double frequency which is
showing up on the neutral.
I suspect that the two hots are not perfectly 180 degrees out of phase to
each other, but how do I convince my client of that and how do we fix it?
The generator is...old...massive...noisy & intimidating of course...and
the type with taps that can be set to choose the type of power delivery
that one wants. I fear that it may not have taps for good ol' single phase
with two opposing hots, however. My client thinks it's set up for
something called "double delta" and showed me a diagram that implies this
to yield "two hots and a neutral" ordinary single phase.
The voltage looks normal from each line to neutral and from line to line.
It's just that puzzling frequency on the neutral that has me concerned.
Charge performance actually cleaned up very well by the time I left the
site but I fear that something is still amiss. Gosh! I didn't measure the
amps on all lines but if the hots are not canceling each other out maybe
the neutral is being required to carry more than just the imbalance
current. Maybe I gotta go back and maybe some pointers or suggestions from
the group would help me do a better job. Is there anything short of an
oscilloscope that can help us figure this out?
Jolliness,
Mick Abraham, Proprietor
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