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Old 03-07-2011, 09:33 AM   #1
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Can I use 3 phase gear for split phase apps

Through my surplus trade I've got a huge selection of Hubble and QOB 3 phase dreamware. I've received a few hints that 3Y phase gear can be used for split phase if wired correctly. What say the code yeah or nay.


(Always making trouble for my AHJ)


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Old 03-07-2011, 11:16 AM   #2
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What does "dreamware" mean? What do you mean by 3Y? Is QOB a Square D breaker?

Of course lots of three phase equipment can be used on single phase. But each item must be addressed separately. List everything you have and what you want to do with them. Then we can tell you.

You can make the list while you wait on your 2011 code book.


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Old 03-07-2011, 12:27 PM   #3
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Oh too much to list. I bought a HUGE trailer worth of new... gear...from Applied Materials, about 1/3
of it residential, 1/3 HUGE 3 phase stuff, and 1/3 light industrial 3 phase. The light industrial 3 phase stuff did not sell,
I've got about 20 plants' worth wired top to bottom.

Here I am deciding whether to go with QO or Hom, when I've got all this great QOB and twist-lock
stuff just staring me in the face.

Actually, the project _may_ be called off due to lack of combo fault breakers, but... just

I'll worry about the item-at-a-time if this project gets out of the conceptual phase.

What I'm hearing so far from you guys confirms the rumors, in theory it's OK to use
3 phase gear for split phase.... guess I've only seen that in downgrades, some silly friend of mine
bought a warehouse which he converted to live/work/bar/club... before I knew him
he "had the 3 phase ripped out", I was like, "Are you crazy? I'd give my right eye for
3 phase at my house, let alone my shop!"

As I recall all the service gear was left 3 phase but... wired for split.

Just thinkin'....

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Old 03-07-2011, 02:16 PM   #4
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yes, you are a mystery.

Your postings don't make a lot of sense.

and whether you can have 3 phase or not is up to you but the local power company. 3 phase has very limited uses for a residential setting. The primary benefit is with 3 phase motors and some 3 phase equipment. Since there is very little 3 phase equipment made for home use, it isn't a big plus, unless you want to use commercial grade 3 phase equipment of course.
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Old 03-07-2011, 05:31 PM   #5
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Well as it happens I do have need for 3 phase. The power co. seemed open to that idea, but I stopped short of getting an estimate. For now I'm using VFD's to about 5 hp and a static converter/x-former up to about 50A for 3 phase Y.

But that's not really my point at the moment. Would you believe I've got a pair of FPE panels to swap out?

So here I am debating whether to go HOM or QO and I'm thinking... this is crazy when I've got all this great, brand new QOB stuff.

Nap you hit the nail on the head... yeah, I want to use this commercial gear, because it's better and to me
basically free. This 135 year old house needs a LOT of work, every $ saved on fixing one safety hazard is
$ that can be spent on the long list of slip and fall hazards, high efficiency appliances, all that good stuff.

Of course I'll be running this by the inspector, just don't want to start planning and suggesting something that
falls flat on its face.

Dreamware... as opposed to nightmareware i.e. FPE panels.

Yeah, I do dream about quality gear sometimes.

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Old 03-08-2011, 02:34 AM   #6
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Not very many homes I know of in states have triphase in the home the only time I have see it in older town distirct or near commercal/industrail location

But in France side where I live triphase is very common item so it is not a issue for us in France but in states it may due some POCO will not provide the triphase unless it pass X number of service entrance size or specail needs then maybe it will set up but to bring in triphase supply they are not cheap at all.

The cost will varies a bit.

If you want triphase just make sure you ask for 208Y120 volts this is the safest system you can use instead of Delta system { you will have to look around the fourm in here or use the search function it will show up a bit with this part }

The answer will be based on NEC ( National Electrical code ) or CEC ( Cananda Electrical code ) or ECF ( Electrique Code France )
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Old 05-05-2011, 10:14 PM   #7
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Eh, turns out all my surplus plugs and receptacles are 3 phase delta. Fugget about it.
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Old 05-06-2011, 08:25 AM   #8
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I heard of people making a 1 phase to 3 phase converter. Basically a 1 phase motor turning a 3 phase "motor" acting as alternator. Kinda clunky and inefficient though and not sure how you'd get the proper voltage out of it.
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Old 05-06-2011, 10:08 AM   #9
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Red Squirrel -- What you talk about is a motor-generator set. These were quite common up until recent years. They ran good but were not very efficient. Last time I looked, many are available surplus. It is possible some are still being made. I quoted a job for the Coast Guard back in the 1990's that called for a motor generator set. Static converters, the modern solid state systems were available, but the millitary wanted to keep the older system becasue they were proven and their technicians knew how to repair them.

Static converters are common for a variety of applications, and can be used to convert 60 to 50 Hz (or visa versa) or single to three phase. The air force and major air carriers use 400 Hz wiring for many systems on their planes to reduce weight. Ground testing of avionics can only be done with a static converter or motor generator set.

Static converters are used to change DC to AC (as in UPS computer back-up systems or photovoltaic systems). Static converters also are built to convert large quantities of AC to DC. We have electric trolley bus service locally, and I was involved when the old motor generator sets which converted 13,000 Volt AC to 600 DC for the buses were changed over to static converters (although a couple of motor generator sets have been left in place for back-up or emergency use.) I also was involved when static converters were used to operate the air conditioning on the buses -- attempts at purchasing reliable 600 Volt DC air conditioners that stood up to time were frustrating. By adding a static converter aboard each bus, we were able to install 208 Y 3-phase air conditiong equipment that was practically off the shelf.

The VFD that Mysteryelectric talks about is also called a Variable Frequency Drive. These are a specialized form of static converter which is designed to operate 3-phase motors at various speeds. Many can operate 3-phase motors on either single or three phase circuits, so if you have a variable speed applications, such as a fan or power tool, or whatever, you can use a VFD to operate a 3-phase motor from single phase power. Locally, we have a lot of industrial surplus and small 3-phase motors are much cheaper than single phase motors of the same horse power and torque rating. Often the 3-phase motors are so cheap that you can buy a motor and VFD and still be cheaper than going single phase all the way.

One issue to think about when using the VFD as a source of 3-phase power is that you need to make sure that the frequency is correct. While "about" 60 Hz may be good enough for a general motor load, it might not work well with precision servo systems or clock-type systems.

Another thing you need to understand about both static converters and VFD drives is that these system can produce 3-phase in a variety of ways, producing anything from square waves to "pseudo sine" or stepped sine waves to some which create very high quality sine waves. The solid state systems which create less than ideal sine waves may not work well with some transformer equipment or other non-motor equipment. Motor-generator sets create true sine waves.
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Old 05-11-2011, 09:02 PM   #10
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Oops, I made and error in my post I should correct. It should read

"For now I'm using VFD's to about 5 hp and a >DYNAMIC< phase converter/x-former up to about 50A for 3 phase Y."
I'll elaborate on the system in a way that complements Perry401's post.

As I see it there are five main types of three phase converters. These are the motor-generator, the dynamic phase converter, the static phase converter, the variable frequency drive or VFD, and the Vector Drive.

Motor generators were widely used where frequency needed to be converted as well, say from 60 hz to 400 hz. They are simple to install and understand and modern designs are fairly efficient. They are heavy, though.

Dynamic phase converters use a motor as a self-exciting generator to generate the third phase. Efficiency is good and full power to the loads is available. Extra passive components, sometimes switched in by relays, are sometimes added for troublesome or sensitive loads.

Static phase converters are basically motor starter circuits that remain attached during run time of the motor. Efficiency in the absolute sense is probably good, but the ultimate power available from the shaft of the motor is reduced to about %60-%70 of nameplate rating. Generally wreak havoc with non inductive loads. Chief advantage is they are cheap, light, good off-the-shelf solution for the common case of being stuck with a 3HP 3P motor on a mill where 2HP would do just fine.

VFD/UPS/Inverter design uses solid state components to synthesize an AC waveform from a DC bus. The DC bus is often derived by simply rectifying the AC input. Ultimately, input and output voltage and frequency parameters can be arbitrary much as with a DC to DC converter, but three cheap and easy tricks are common. One is to draw power from single phase and convert to three phase. Another is to half-wave rectify (is that the right term?) the AC input to get a 2X bus voltage, much as "universal input" switching power supplies do. Finally they can take advantage of the fact that the peak input voltage is 1.414X the input RMS voltage. These three tricks can be combined ie: to get 277V three phase from 110V single phase. Ironically, many VFD's must be derated when supplied with single phase or 120V power, you can expect to take a %30 hit in the larger sizes. This is not a real limitation of the technology, but of the components used: to get full power from single phase larger capacitors and PFC components must be used, increasing costs. The market is competitive not only with respect to costs but also to size and weight and reliability restrictions, so fitting with %30 larger caps to capture a niche market can't be rationalized. Above about 5HP it's hard to find single phase input types, though I suspect the only real difference in the design is that above 5HP. loss of an input phase is considered a hard fault that can't be ignored via user-accessible setting. As mentioned the quality of the output waveforms is also quite arbitrary with these designs, with economy favoring cheaper design and worse waveforms almost monotonically. Fully analog VFDS were common but now are largely replaced by uP controlled units. Sometimes rotary encoders or other technologies are used to compensate for slip. Some efficiency is lost in the switches and some to control circuitry, these figures vary widely but for most modern commercial designs the break even point is about .5-2HP: that is to say, if you are hoping to save energy by running a .5HP at %25 input power, you would actually save energy by running the motor flat out and dropping the VFD from the design. If on the other hand you think you might benefit from running a 2HP pump at 1HP most of the time with a VFD, you're probably right. VFD's are quickly finding their way into consumer devices, and for these small scale applications (by contrast) designs can achieve both high absolute efficiency and very high efficiency relative to the variable speed technologies they replace. New designs have excellent power factor, and are often used for PFC alone, and/or for their soft-start ability. Most digital designs can run from the low Hz up to 400Hz or more and therefore provides some motor speed control: however, the RMS voltage is typically varied linearly over the frequency range to avoid excessive power dissipation by the induction motor at low speeds, so available torque varies widely with frequency and thus speed.

Finally there is the sensorless vector drive. The vector drive uses matrix computations to monitor, model, and control the position of a traditional three phase induction motor rotor in real time, without using an encoder. This allows interesting possibilities such as constant torque operation at a wide range of speeds, active slip compensation (ie: no slip), active braking, and servo-like control. Theoretical efficiency can be very good, again in practice varies widely based on design and application. To emphasize, you can install these units in-line with existing plain old 3P induction motors and get these advantages without worrying about attaching a retrofit shaft encoder. Sensorless vector technology is essentially a software upgrade to the more sophisticated VFD controllers. The marketing departments of most manufacturers have conspired to ensure that you will pay about %30 more for these perks on otherwise similar hardware.

Well, I was going to describe my system so you could see how some of these weave together, but I gotta get back to it, whatever it was...



Last edited by mysterylectric; 05-11-2011 at 09:39 PM.
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