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480 v hps lighting circuit #205541 03/02/12 04:12 PM
Joined: Dec 2004
Posts: 78
C
Cinner Offline OP
Member
I was working on a 480v hps lighting circuit and went to turn the circuit off to change the fixture but still measured 66 volts to ground on each leg. Does. Any one know why this would be?

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Re: 480 v hps lighting circuit [Re: Cinner] #205542 03/02/12 05:15 PM
Joined: Jul 2004
Posts: 783
L
LarryC Offline
Member
What type of meter did you measure the voltage with? If it is an electronic meter with the high input impeadence, it will measure "ghost" voltages. These "ghost" voltages are due to the wires traveling next to energized wires. Both set of wires are acting as a transformer.

Measure the voltage with a Wiggy or equivalent and the voltage will PROBABLY disappear. If they do not disappear, you have a problem. If the voltage does disappear then you are measuring ghost voltages.

Re: 480 v hps lighting circuit [Re: Cinner] #205543 03/02/12 05:22 PM
Joined: Dec 2004
Posts: 78
C
Cinner Offline OP
Member
Measured it with a fluke multimeter.

Re: 480 v hps lighting circuit [Re: Cinner] #205545 03/02/12 08:37 PM
Joined: Jun 2004
Posts: 1,273
T
Tesla Offline
Member
Fluke multimeters ARE high impedance testers.

You need to use an old-style analog meter to load down these induced voltages. Since there is no current flow, it's really a capacitive effect.



Tesla
Re: 480 v hps lighting circuit [Re: Cinner] #205547 03/02/12 10:21 PM
Joined: Apr 2002
Posts: 7,235
HotLine1 Offline
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Cinner:

You need a 'Wiggy', or any other brand solenoid type tester, or an analog multi-meter.


John
Re: 480 v hps lighting circuit [Re: HotLine1] #205550 03/03/12 03:26 AM
Joined: Jul 2007
Posts: 1,335
S
sparkyinak Offline
Member
WIGGGGGGGY!!! I carry one in my pouch just for that


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Re: 480 v hps lighting circuit [Re: Cinner] #205556 03/03/12 05:36 PM
Joined: Feb 2004
Posts: 1,437
Lostazhell Offline
Member
This happens in a cogen I work in alot.. 480V wiring from VFD loads seem to induce voltage on other conductors more than anything.. HID loaded circuits have the same tendency


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