[RE-wrenches] Possible genset configuration error...but how do I convince my client!

[William Miller]

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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