Welcome! Please use the navigational links to explore our website.
PartsASAP LogoCompany Logo (800) 853-2651

Shop Now

   Allis Chalmers Case Farmall IH Ford 8N,9N,2N Ford
   Ferguson John Deere Massey Ferguson Minn. Moline Oliver

Attention Forum Users: On the 28th of December 2023 at 9:00am Central Time, we will be taking the forums down for maintenance while we prepare the new forums for your use. Please click here for more information.

Tool Talk Discussion Forum

Elecrical 3 Phase question, No Neutral?

Welcome Guest, Log in or Register
Author 
BarryKS (UK)

12-20-2005 08:48:15




Report to Moderator

I have just been repairing the cable to a three phase motor and i have a problem... I wanted to run a single phase motor off one of the phase wires as a temporary fix but i cannot find the neutral wire?

The wire colours are as follows Red-(Phase R),Yellow (Phase Y), and Blue (Phase B) but there is no Neutral (Black).

How does a motor run without a Neutral?, Other parts of the barn electrics have a Black Neutral, although some of the live phase wires seem to consist of 3 Reds.

Thanks for your help,
BarryKS (UK)

[Log in to Reply]   [No Email]
Kevin Bismark

12-22-2005 15:36:09




Report to Moderator
 Re: Elecrical 3 Phase question, No Neutral? in reply to BarryKS (UK), 12-20-2005 08:48:15  
the more I think about this, the best response I could have given was to call a real electrician to come out and see what you really have there, makes the hair on the back of my neck stand up when I see some of these "temporary" fixes done, they last for years, yup, most of the tempory fixes last for years, you go out the next time they have trouble and no fuses, or way overfused, no ground on anything, using building steel or water pipes as a neutral, just try not to burn anything down or kill anyone with the temp fix..

[Log in to Reply]  [No Email]
buickanddeere

12-20-2005 18:54:06




Report to Moderator
 Re: Elecrical 3 Phase question, No Neutral? in reply to BarryKS (UK), 12-20-2005 08:48:15  
If the motor is 208 three phase then a 240 single phase motor will sort of work but it needs to be oversized to carry the load. E.g. a 5HP 240 motor when fed 208 makes about 3HP before over heating. Is you hydro service an isolated delta, one of those crazy grounded deltas or a Y system? In England they run 50Hz 240 single phase or 416 three phase but often call it 380. Similar to how 440 and 480 or 550 and 600 get lumped together. For a while in Toronto during the 1960's there was a brief fad to run lights and office loads from 240V single phase and the motor loads from 416V 60Hz three phase. The idea was to make the power service simpler and cheaper. It never really caught on. Do not do the dumb *ss farmer trick of taking one live line to the single phase motor.And tieing that single phase motor's neutral to a water pipe etc that goes back to earth/ground. Instead of connecting to a real neutral coming from the distribution panel neutral bar.

[Log in to Reply]  [No Email]
MarkB_MI

12-20-2005 18:46:33




Report to Moderator
 Re: Elecrical 3 Phase question, No Neutral? in reply to BarryKS (UK), 12-20-2005 08:48:15  
The previous posts were good. I just want to add that you should check the phase-to-phase voltage to make sure it's correct for your single phase motor. If it's not, you may need to run a neutral.

For reference, the phase-to-phase voltage will be 1.73 (the square root of 3) times the phase-to-neutral voltage. So if the phase-to-phase voltage is 208 volts, the phase-to-neutral voltage is 120 volts.

If you're in the UK, be careful about advice you get here. Your standards are totally different than those in North America (and just about everywhere else, for that matter).

[Log in to Reply]  [No Email]
Kevin Bismark

12-20-2005 16:54:37




Report to Moderator
 Re: Elecrical 3 Phase question, No Neutral? in reply to BarryKS (UK), 12-20-2005 08:48:15  
3 phase motors do not have a neutral, no need for it wye or delta it doesn't matter, the motor is a straight 3 phase, if you want to temp it you can just use the wires you have use 2 for ungrounded conductors and the other as an equipment ground if you need it, they must have been using the metal pipe for an equipment ground before, or if you really do need a neutral use one for the ungrounded conductor and another for a neutral and the pipe or the other wire for an equipment ground

[Log in to Reply]  [No Email]
JHesler

12-20-2005 15:51:51




Report to Moderator
 Re: Elecrical 3 Phase question, No Neutral? in reply to BarryKS (UK), 12-20-2005 08:48:15  
You have a Delta setup. You can get your single phase off of any pair of two wires but it won't be ground referenced like you're used to with single phase derived from a Wye connection. To get a true ground referenced single phase you would need to use an isolation tranformer with one of the secondary leads tied to ground. For a temporary fix, you probably don't need any ground reference on a motor because the windings should be insulated from ground. Just make sure you ground the motor case.

[Log in to Reply]  [No Email]
tech4

12-20-2005 09:27:53




Report to Moderator
 Re: Elecrical 3 Phase question, No Neutral? in reply to BarryKS (UK), 12-20-2005 08:48:15  
I am running a risk of being wrong since I am not familar with UK 3 phase but some general information. A 3 phase motor does not normally need a neutral since the current flow is between the phases. I think the standard 3 phase voltage in UK is 400 v but not sure. If your supply is from a Y sorce then there will be a neutral that would only be required for single phase equipments. I am not sure what your single phase voltage would be but you could measure with a voltmeter and see if your single phase motor has the same voltage requirements. If you find the voltage correct then for a temporary fix and understanding that it is not up to code and safety rules - you could swap one of the phase wires to the neutral bus for a test or short peroid to get your single phase motor running. This is just general information and you might find a local electrician to help you.

[Log in to Reply]  [No Email]
[Options]  [Printer Friendly]  [Posting Help]  [Return to Forum]   [Log in to Reply]

Hop to:


TRACTOR PARTS TRACTOR MANUALS
We sell tractor parts!  We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today. [ About Us ]

Home  |  Forums


Copyright © 1997-2023 Yesterday's Tractor Co.

All Rights Reserved. Reproduction of any part of this website, including design and content, without written permission is strictly prohibited. Trade Marks and Trade Names contained and used in this Website are those of others, and are used in this Website in a descriptive sense to refer to the products of others. Use of this Web site constitutes acceptance of our User Agreement and Privacy Policy

TRADEMARK DISCLAIMER: Tradenames and Trademarks referred to within Yesterday's Tractor Co. products and within the Yesterday's Tractor Co. websites are the property of their respective trademark holders. None of these trademark holders are affiliated with Yesterday's Tractor Co., our products, or our website nor are we sponsored by them. John Deere and its logos are the registered trademarks of the John Deere Corporation. Agco, Agco Allis, White, Massey Ferguson and their logos are the registered trademarks of AGCO Corporation. Case, Case-IH, Farmall, International Harvester, New Holland and their logos are registered trademarks of CNH Global N.V.

Yesterday's Tractors - Antique Tractor Headquarters

Website Accessibility Policy