ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Top Posters(30 Days)
Potseal 11
Recent Posts
600 KW 120/208 3 Phase Y protection
by Yooperup. 07/24/17 12:20 PM
1913 American Electrician's Handbook
by gfretwell. 07/20/17 01:08 PM
Green House wiring
by ghost307. 07/20/17 09:10 AM
Permit Snafus...AHJs and Contractors Jump in
by HotLine1. 07/18/17 08:06 PM
New in the Gallery:
SE cable question
Popular Topics(Views)
239,362 Are you busy
174,822 Re: Forum
167,211 Need opinion
Who's Online Now
0 registered members (), 80 guests, and 3 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate This Thread
#30415 - 10/17/03 09:39 PM Interesting 3 phase results  
Clyde  Offline
Member
Joined: Oct 2003
Posts: 31
Leamington
I had something new happen to me last night, I've asked two other electricians and they don't have an answer for me either. I had a 3 phase, 4 wire 600 volt splitter, and I needed to power a 347 volt light, while I changed a single phase 120/240 volt x-former to a three phase 120/208. When I turned on the disconnect for the light, the light didn't come on. I checked the voltage and found 120 volts on the phase I was hooked to, I found 780 volts on another phase and over 800 volts on the next phase. I tried to hook the light to a different phase and had the smae results. With no lights hooked up, everything is normal. Has anyone seen this before.
Thanks.


Work Gear for Electricians and the Trades

#30416 - 10/17/03 11:38 PM Re: Interesting 3 phase results  
Electric Eagle  Offline
Member
Joined: Apr 2002
Posts: 914
Alpharetta, GA
It sounds like a loose connection somewhere. Possibly in the splitter or even all the way back to the poco's xfmr. You said 4 wire, so it could be the neutral, I've seen similar results with a loose neutral before.


#30417 - 10/18/03 12:03 AM Re: Interesting 3 phase results  
Scott35  Offline

Broom Pusher and
Member
Joined: Oct 2000
Posts: 2,707
Anaheim, CA. USA
I agree.
Sounds like you are reading the resultant voltage of Capacitive Coupling (if you are reading L-G and getting the wierd readings as stated).

Make sure the Common Grounded Conductor (AKA "neutral") is connected properly between source and load(s).
Also make sure the Equipment Grounding Conductor is connected properly between source and load(s).

Sounds like you have both - an open Noodle and an open Eq. Grounding Conductor, only the EGC is physically connected to earth ground somewhere, but not connected to the source's Grounded Conductor.

Just guessing... [Linked Image]

Let us know the outcome!

Scott35


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

#30418 - 10/18/03 07:16 PM Re: Interesting 3 phase results  
Pinemarten  Offline
Member
Joined: Aug 2003
Posts: 123
Edmonton, AB, Canada
Another thought or two....
Are the ballast taps marked correctly, is the ballast capacitor hooked up correctly, does the voltage change when the lamp is in or out of the socket?
I think there are drawings in the technical reference section.


#30419 - 10/18/03 09:09 PM Re: Interesting 3 phase results  
Clyde  Offline
Member
Joined: Oct 2003
Posts: 31
Leamington
I did check the neutral today and did find a fair amount of resistance between the neutral buss and ground. Perhaps this is the problem.

I also found out that the building is currantly fed with an open delta configuration due to a destroyed transformer. That shouldn't cause a problem though.

I appreciate your responses guys.


#30420 - 10/23/03 05:01 PM Re: Interesting 3 phase results  
Clyde  Offline
Member
Joined: Oct 2003
Posts: 31
Leamington
After a little more research, I've discovered that the open delta configuration is the problem.

When an open delta configuration is used, only three wires are available from the transformers. Leaving you without a center-tapped neutral. I'm still learning every day.

Thanks.



Member Spotlight
Admin
Admin
NY, USA
Posts: 3,447
Joined: October 2000
Show All Member Profiles 
Featured:

2017 Master Electrician Exam Preparation Combos
2017 NEC Electrician
Exam Prep Combos:
Master / Journeyman

 

Shout Box
Powered by UBB.threads™ PHP Forum Software 7.6.0
Page Time: 0.013s Queries: 14 (0.003s) Memory: 0.7767 MB (Peak: 0.9204 MB) Zlib enabled. Server Time: 2017-07-27 16:43:53 UTC