Author Topic: What makes a generator single phase or three phase?  (Read 11007 times)

MacGyver

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Re: What makes a generator single phase or three phase?
« Reply #15 on: December 06, 2008, 04:11:38 PM »
Regarding '3 phase welders'.

I think you will find they only use two phases.  'Three' phase ones can drive the meter backwards, I have been told by an electricity board electrician.

Regards, RAB

Uhhh.... I've been inside probably a hundred or more 3-phase welders, and they've all run on genuine 3 phase. I've NEVER seen a 2-phase welder. Single phase yes. but 2 phase... never.
How would a 3-phase welder possibly drive the meter backwards?

Your electrician friend is either pulling your leg or he's utterly clueless...
Steve

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Stan

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Re: What makes a generator single phase or three phase?
« Reply #16 on: December 06, 2008, 08:23:56 PM »
That's the kind of welder I want, one that will run my meter backwards, I'll use it all day long.  ;D ;D ;D
Stan

rcavictim

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Re: What makes a generator single phase or three phase?
« Reply #17 on: December 06, 2008, 11:02:09 PM »
That's the kind of welder I want, one that will run my meter backwards, I'll use it all day long.  ;D ;D ;D
Stan

Of course we all would!  Unfortunately I think it belongs in the category of urban legends like the alleged 200 MPG carburetor.
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mobile_bob

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Re: What makes a generator single phase or three phase?
« Reply #18 on: December 07, 2008, 12:21:58 AM »
funny you should mention the 200mpg carburator

it is no urban legend, it actually existed :)

i found the book down at the tacoma main library about 10 years ago,
it had the technical drawings and all the details

the inventor admitted the following from memory

"i don't think my invention will ever have practical application, because no one will want to drive a car
with such a carburator"

basically the engine he had it on, would make something  like 150mpg, out on the flat highway, with a strong
tail wind, tires aired up to something like 80psi, etc etc.

the thing had no accelerator pump, no power valve and as such would take something over a mile to get up
to highway speed,, all the while the driver had to fiddle with remote adjustments of timing and other crap associated
with the carburation just to keep the thing barely running.

so it did exist, it just wasn't at all practical
the engine probably started out life as a 150hp plant, and after being retrofit with the supercarb probably didn't make 3hp

just thought i would throw that out there,, i was actually shocked when i came across the little paperback book at the main library

he probably made more selling the book than he ever made on the carb idea.

bob g
otherpower.com, microcogen.info, practicalmachinist.com
(useful forums), utterpower.com for all sorts of diy info

matt

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Re: What makes a generator single phase or three phase?
« Reply #19 on: December 08, 2008, 12:02:25 AM »
Quote
funny you should mention the 200mpg carburator

it is no urban legend, it actually existed  :)

I'll second that!

I have heard exactly the same info before.

Bob G knows his automotive history well!!!

regards,
matt

lowspeedlife

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Re: What makes a generator single phase or three phase?
« Reply #20 on: December 30, 2008, 12:38:15 AM »
I can't remember seeing anything that ran off of "2 phase" power except condominiums, they will bring 208 3 phase into the building & " split it up", using A & B phases' to run the first condo panel, B & C to run the second, A & C to run the third & so on, giving you 2 phases of 208 volts on each panel.

    scott r.
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adhall

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Re: What makes a generator single phase or three phase?
« Reply #21 on: December 30, 2008, 05:32:31 AM »
Lowspeedlife:

208 V is convenient because you have 120 V to neutral for small loads and 208 V for bigger loads like stoves, water heaters, etc.

In industrial applications (in the U.S., at least) it is common to feed 208 V / 3-phase power to a breaker panel and then populate the panel with a variety of single pole, two pole, and three pole circuit breakers according to the needs of the loads.

For what it's worth, there actually was a 2-phase system developed way back in the early days of electricity. I believe it predated the 3-phase system. This system required four wires -- two for each phase, and the voltages in the two phases were 90 degrees out of phase with each other. The 3-phase system is superior in that it only requires 3 wires.

Best regards,
Andy Hall
JKSon 6/1, 5 kW ST Head, 1992 Dodge RAM Cummins 5.9L Turbodiesel, 2001 VW TDI 1.9L Turbodiesel, 2006 Jeep CRD Turbodiesel, Yanmar FX22D Diesel Tractor

oliver90owner

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Re: What makes a generator single phase or three phase?
« Reply #22 on: December 30, 2008, 09:05:14 AM »
Your electrician friend is either pulling your leg or he's utterly clueless...

Spoke to him fleetingly over Xmas.  He assures me that the power generators do not like 3 phase welders on the system for metering reasons.

 Engine driven - fine - but fed from the mains is 'at least not encouraged'.  He is a reliable and well-informed ex regional electricity board leccy (retired), so should know what he is talking about.

Regards, RAB

MacGyver

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Re: What makes a generator single phase or three phase?
« Reply #23 on: December 30, 2008, 06:52:02 PM »
Your electrician friend is either pulling your leg or he's utterly clueless...

Spoke to him fleetingly over Xmas.  He assures me that the power generators do not like 3 phase welders on the system for metering reasons.

 Engine driven - fine - but fed from the mains is 'at least not encouraged'.  He is a reliable and well-informed ex regional electricity board leccy (retired), so should know what he is talking about.

Regards, RAB


Well, I can be fooled about a lot of things...  but I've done serious time repairing welding equipment for a living and have the T-shirt and Lincoln and Miller ball caps to prove it, so I don't fool quite so easy on that one....

From 1980 -1984 I worked for a large fabrication shop in the SF Bay Area (Northwestern Equipment & Supply Co.) that in addition to having a rather large steel fabrication shop, also rented, sold, and serviced industrial welding equipment and supplies. We had over 200 welding machines in our rental fleet, plus dozens more in the fabrication shop.  But no 2-phase machines in the lot.

During those years I serviced, installed, repaired literally 100's of welding machines belonging to us or our customers. Almost exclusively 3-phase or gas/diesel driven machines from 200 to 2000+ amps output.
I've worked on equipment in a huge variety of Bay Area industrial businesses... every oil refinery in the bay area,  Pacific Steel Casting , TASCO valves, Mothers cookies (RIP), OAK and SFO airports, lots of work at Moffet field including the big wind tunnel and that enormous "hanger 1". 
I serviced machines at the old Airco Welding Institute in Oakland (they had about 60 3-phase machine in the fleet for their students).
I've fixed machines in countless smaller shops that few folks have heard of. But in ALL of them, the welding equipment was genuine 3-phase. Never ever seen a 2-phase machine or a 3-phase machine that only used 2-phases.

I spent 4 days at the Lincoln Electric Co. Factory in Ohio, to become a "factory certified technician". In 4 days of class discussion about welding equipment no one EVER mentioned any 2-phase equipment, or any metering problems with the millions of 3-phase welders in the world.
I walked away from Lincoln with about 50lbs of books and service manuals for all of the then current Lincoln welding equipment. Any 2-phase stuff in there?  Nope.

(Later, I consulted with Bill Urbanski and the senior designers at Lincoln and proposed several changes to the control circuitry of the LN23-P wire feeder and one of the large Sub-Arc welders that was new at the time.  My suggestions were incorporated into the newer versions of those machines and my SJD initials appear on schematics in the service manuals for those machines.)   ;D

From 1985-87 I worked for a smaller company in Hayward doing basically the same thing. Still never seen any 2-phase welders.

In the early 90's I did a lot of work for 2 large stainless fabrication shops that made wine fermenting tanks and equipment.  I repaired dozens of genuine *3-phase* welders for those folks.
By '97 I'd pretty much moved away from the equipment repair scene, so my direct experience ends there.

I'm pretty sure that if 2-phase machines commonly existed (or 3-phase machines that only "use" 2 -phases) that I would have seen or at least heard about ONE of them in my lifetime...

Most 3 phase welders are just a simple 3-phase transformer that feeds a standard 6 diode 3-phase rectifier then regulates the current/voltage appropriately. There's absolutely nothing in there that's gonna "fool" anyones metering equipment.

Here's a schematic for a Miller DeltaWeld 650.  3-phase, 240/480 volt input. The genuine 3-phase input is clearly show at the left side...

http://www.weirdstuffwemake.com/sweetwatergems/geek/misc/deltaweld_650.gif

Please ask your friend to send me a schematic for any "2-phase" welding machine, or provide me with a make/model# of one so I can look it up for myself.  Seeing is believing. :)

Steve

JKson (PS) 6/1 'roid & ST 7.5

M61hops

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Re: What makes a generator single phase or three phase?
« Reply #24 on: December 30, 2008, 09:15:26 PM »
Hi RAB, I would bet money that utility companies would really like to keep all their phases ballanced as close as possible so I don't understand the "not encouraged" coment  :o !  Would you please ask your friend to explain the reasoning for his belief and share it with the list?  Might be an interesting perspective!                         Leland
I pray everyday giving thanks that I have one of the "fun" mental disorders!