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#40878 08/08/04 06:58 PM
Joined: Aug 2004
Posts: 2
M
marxie Offline OP
Junior Member
I recently moved my woodworking machines from a large residential garage into a commercial shop building. All machines are single phase 230 volt. The shop has 3 phase power as well as "220" single phase outlets. Things seemed to be working fine for a few weeks then my dust collector wouldn't come up to speed and everything else was running under-powered. I swear it all ran fine until I turned the machines off to answer a phone call. I metered the outlets and the panel and I get 122 volts per leg, but only 214 across the legs. Same thing at the panel. My old shop at home gave me readings of 122 volts per legand 244 across the two which made sense to me. Why am I getting only 214 at the new shop? I replaced the circuit breaker, filed the contacts and all wire is at or above code for the runs/amps of the motors. My shopmate thinks that the utility company has transformers at the pole that are only supplying 208 volts cause "that's what older machines ran at." and it's up to me have my machines tweaked to run at this voltage. I'm just wondering if there could be another explanation since I can't believe I can't get 230V in a commercial building as well as the sudden change in performance. Any suggestions would be greatly appreciated!!!

#40879 08/08/04 07:25 PM
Joined: May 2001
Posts: 717
G
Member
Marxie,
Commercial 3phase, 4 wire, Wye connected power (which is what you have) is nominally 120/208 volts. Most commercial equipment will be rated for a 10% tolerance. If your machines won't take it, you have two basic options

1 - change the motors to 208 volt rated

2 - install buck/boost transformers

If you select the first option, someone like Graingers can match most any motor you need if you supply them with ALL the nameplate data.

1-800-323-0620 or www.grainger.com

There are plenty others as well.

Good Luck

#40880 08/08/04 09:52 PM
Joined: May 2004
Posts: 697
D
Member
I've been installing 3-phase services with interior 120/208/240 volt wiring for the past year. Your question is not in my field of experience, but I'd call the power company and ask if they can make an adjustment at the transformer to bring the voltage up.

Dave55

#40881 08/08/04 10:14 PM
Joined: Jul 2004
Posts: 625
S
Member
Dave55, that sounds like a good trick. What are they doing? I'll hazard the guess that they're supplying four phases, at 0, 120, 180, and 270 degrees? Although, I've never heard of a panel that would support that.

#40882 08/08/04 11:08 PM
Joined: Apr 2002
Posts: 914
E
Member
214 is close enough for most equipment rated at 230 to run properly. The problem normally comes when a motor/controls needs 208, but has 230 or 240. If it is causing a problem, I'd install a buck/boost transformer.

Check with the manufacturer of your equipment, you may be able to run it on 3 phase and improve the performance.

#40883 08/09/04 02:32 AM
Joined: May 2003
Posts: 2,876
E
e57 Offline
Member
Anyone know if the make a "phase un-converter"?

OK!


Quote
I replaced the circuit breaker, filed the contacts

Don't know where to start there... Hope you're not filing the buss work?

Besides this obvious system and voltage issue you have. (Although, if you check all of your equipment, some will have dual rateings. ie 208/240 And the ones that don't should still operate ok for some time, with some efficiancy loss and higher operating amperages, until you can correct the motors.)

But, you mentioned this that caught my eye...

Quote
Things seemed to be working fine for a few weeks then my dust collector wouldn't come up to speed and everything else was running under-powered. I swear it all ran fine until I turned the machines off to answer a phone call. I metered the outlets and the panel and I get 122 volts per leg, but only 214 across the legs.
FYI that voltage sounds fine... (for 3 phase wYe) Assuming you checked this voltage "no load"? Check a piece of equipment that your not really attached to,breifly, (after start up) "under-load", and you get any one phase at higher >5%, or 2 <10% at the panel. Then you may have different problems! For starters... severe un-balance, systems/transformer over-load, or neutral/phase loss. If this happened all at once, after everything 'seemed to work fine', then something is up!

Not sure what your electrical expertize may be? But it sounds like you need a good "3 phase and motors troubleshooting" guy.

[This message has been edited by e57 (edited 08-09-2004).]


Mark Heller
"Well - I oughta....." -Jackie Gleason
#40884 08/09/04 02:43 AM
Joined: May 2003
Posts: 2,876
E
e57 Offline
Member
Oh, most people would kill for 3 phase wye 208!


Mark Heller
"Well - I oughta....." -Jackie Gleason
#40885 08/09/04 07:25 PM
Joined: Apr 2001
Posts: 507
G
Member
Call your local electrician before you burn up your motors and it gets really expensive.

#40886 08/09/04 08:22 PM
Joined: Apr 2002
Posts: 2,527
B
Moderator
marxie—You may be out of luck given your location¡­likely PG&E, and bound by their Electric Rule 2 [www.pge.com/tariffs/doc/ER2.doc] which permits them as low as 197 volts at their meter. Unfortunately, they are unlikely to 'adjust' their equipment to accommodate your request, for that may cause problems with other customers on the same transformer that have routinely installed 208V gear, and raise heck with your and others' 120V stuff.

In the fine print, your servce is termed: A modification of a three-phase, four-wire system is­ a 120/208Y-volt service for singlephase, three-wire, open-wye applications. Another term is "network". The building is fed from a 208Y/120V-secondary bank. 122&#8729;1.732 = 211V, and well 'within spec' as far as the utility is concerned. Nowadays commercial and light-industrial neighborhoods are more likely 208 than 240V.

One out may be to have a qualified electrical contractor install autotransformers. 240:24 versus 240:32 are common ratings, sized depending on how low the usual '208' is.

Aside from autotransformers on individual equipment—carefully applied, a single autotransformer might be used to serve multiple machine tools. Don't make the mistake of serving any 120V loads from the autotransformer.




[This message has been edited by Bjarney (edited 08-09-2004).]

#40887 08/09/04 09:13 PM
Joined: Jan 2003
Posts: 4,391
I
Moderator
Quote
call the power company and ask if they can make an adjustment at the transformer to bring the voltage up.

The power company could bump up the voltage but as Bjarney pointed out it will effect the 120 volt equipment.

Raise the 208 volt system up to 230 volt and you will have 132 volts at your 120 volt equipment. Even if you can live with that your neighbors might not want to. [Linked Image]

Bob


Bob Badger
Construction & Maintenance Electrician
Massachusetts
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