Neutral Cancelling Voltage

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fatuus

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Location
Virginia
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Electrician
Here is the scenario. The voltage at the lighting panel is 480/277 as it should be. When a load as small as one light fixture is added the following test results are observed;

A phase 0 Volts to ground
B phase 277 Volts to ground
C phase 277 Volts to ground.

The panel is the load/secondary of a lighting inverter. Problems like this always seem to be the neutral. Will you help me to articulate what causes problems like this, with wonky voltages happening because of neutral issues? Thanks y'all.
 
ptonsparky said:
What is a lighting inverter?

Is it always A that drops to 0, when the load is applied to A,B, or C?
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Lighting inverter is battery emergency backup connected to a maintenance bypass circuit. We only put load on A phase to get these wonky readings. I would lie to begin a conversation about neutral issues in general here if possible.
 
If a neutral is compromised, when one phase is loaded and its voltage to neutral drops, the voltage on the others will rise depending on where you are measuring.
 
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