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#128407 - 02/23/03 10:27 PM Ground fault current
Andre M Offline
Junior Member

Registered: 02/22/03
Posts: 8
Loc: Wheeling, IL
Problem recently posted for my class:

Heating element rated 240v 4800W (20A) has been connected to 120/208v grounded "Y" system between two phases (208v). - Everybody egrees now 3600W / 17.3A.
1. Midpoint of the element is shorted to ground assuming 0 (zero) resistance of ground fault. What total power is rreleased during ground fault?
2. What current flow to ground?

What is your opinion on asked numbers? - Is it too hard for master electrician?

Andre

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#128408 - 02/24/03 04:46 AM Re: Ground fault current
Gwz Offline
Member

Registered: 04/29/02
Posts: 199
Find ohms of the original.

R = E / I, R = 240V / 20A, R = 12 ohms.

Now this is used on a 208/120V system.

The Neutral of 208/120V system is intentionaly connected to Ground and you noted 0 restistance to ground, thus the circuit at midpoint is being operated as on 120V system.

1/2 of the 12 ohms is 6 ohms.

I on the 120v as now operating is;

I = E / R, I = 120V / 6R, I = 20A on each of the two sections of the ground faulted 240, 4800W, 20A heater operated on the 208V system.

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#128409 - 02/24/03 06:05 AM Re: Ground fault current
Andre M Offline
Junior Member

Registered: 02/22/03
Posts: 8
Loc: Wheeling, IL
Yes, thanks. Now a little harder second question. Find ground current.

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#128410 - 05/25/03 03:48 AM Re: Ground fault current
Ichabod Offline
Member

Registered: 05/24/03
Posts: 26
Loc: Statesboro, GA, USA
20 Amps.

Ichabod

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#128411 - 05/31/03 07:00 PM Re: Ground fault current
Scott35 Offline

Broom Pusher and
Member

Registered: 10/19/00
Posts: 2724
Loc: Anaheim, CA. USA
Should I draw this one up and post it in the Tech. Reference section?

Scott
_________________________
Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!

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#128412 - 06/01/03 06:36 AM Re: Ground fault current
Ichabod Offline
Member

Registered: 05/24/03
Posts: 26
Loc: Statesboro, GA, USA
Yes Scott, please do.

Ichabod

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