680 volts?

[buzzlectric]

while checking for a blown fuse today i got 680+/- volts across the fuse/socket ends, this is the primary side of transformer 480 x 208/120 i have seen some odd voltages before , but never higher than the supply voltage.

any ideas?

 

[bphgravity]

Re: 680 volts?

Where does the supply come from that feeds the transformer? Can you shut down the service and check the utility voltage?

Did you do a meter check to ensure proper operation?

 

[buzzlectric]

Re: 680 volts?

meter is fine, plant supply voltage is 480/277 , and after replaceing the fuse all worked fine, had normal voltages, only seen this when fuse was blown or removed.

 

[hardworkingstiff]

Re: 680 volts?

Originally posted by buzzlectric:


any ideas?

Seems like you were getting the peak voltage reading instead of the RMS. Were you working one fuse only with the other two still installed and working? Maybe the coil on the transformer held the voltage up so you read the peak instead of the RMS?