PDA

View Full Version : 3 phase power



spkrman15
10-28-2014, 09:27 PM
Hey everyone,

A long time ago, I got talking to some people on here about rotary phase converters, Static phase converters and VFD's. Someone mentioned a true 3 phase (generator / creator). A system that creates 3 phase power like that at the hydro line. I am not talking about a diesel 3 phase generator like a Cat or a Kholer but something like a cabinet that creates balanced true 3 phase power. Does that ring a bell with anyone?

Rob :)

lakeside53
10-28-2014, 09:46 PM
"Phase Perfect". I have a 10hp (36 amp) version installed - no looking back ... "better than utility".

http://www.phaseperfect.com/

Quite different to a "vfd". A Phase Perfect can pass regenerative power back to the utility.

Don Young
10-28-2014, 09:47 PM
Variable Frequency Drives (VFD's) and other inverter drives of that type create balanced 3 phase sources. Some company (PolyPhase?) currently markets what I think is a fixed frequency version. There are also motor-generators that do the same thing but I think they are pretty much obsolete. There are also a lot of laboratory 3 phase generators that will produce power with variable parameters.

Edit: "Phase Perfect" is probably what I was thinking of.

mike4
10-28-2014, 10:00 PM
I prefer the Gensets as they can keep everything running normally , like storm season when power drops out regularly without warning , or some fool runs into a power pole .

Yes the initial investment is up there depending on the size of the equipment , but after that the cost of fuel etc is insurance to me , and peace of mind .

I know that the VFD's and other electronic converters are economical to run ,if you dont mind being in the dark for hours or days.

Michael

spkrman15
10-28-2014, 10:03 PM
Yes I believe it is phase Technologies I was thinking of. Does anyone have experience with that equipment?


Are they better than a regular static phase converter?

Cost? (Reasonable for what you get?)

Rob :)

PStechPaul
10-28-2014, 10:18 PM
An important difference is that the Phase Perfect uses one leg of single phase power and generates a third leg at 60 degrees so that the resulting three phase power is the same voltage and frequency as the utility power. But if you want to control a motor with variable speed a VFD is needed. The Phase Perfect might be able to provide a good three phase source for a high power VFD, but up to a couple of HP or so, most VFDs can run OK on single phase. The main problem is the need for a rectifier and capacitors to hold the DC link voltage above a minimum level, and that can cause poor power factor and excess current on the AC line. This can be improved with a PFC circuit.

lakeside53
10-28-2014, 10:31 PM
Yes I believe it is phase Technologies I was thinking of. Does anyone have experience with that equipment?


Are they better than a regular static phase converter?

Cost? (Reasonable for what you get?)

Rob :)


A static phase converter is pathetic in comparison to just about any other method- it's just a three phase motor starter, then the motor runs poorly on single phase. Advantage- dirt cheap. Disadvantage - maybe you can get 50% of the rated motor power before overload (not the 66% touted...).

A Phase Perfect produces utility quality power, and is close to bullet proof. Many is use around here. As I said in my prior post, I have a 10hp version (guaranteed to start and run a10 hp motor) or 36 amps continuous at 240 volts delta. Dead easy to install, then forget it. About $2500-2900 in the USA for that version. Expensive, but a steal for what you get.

spkrman15
10-29-2014, 07:19 PM
Thanks Guys,

I appreciate the information and feedback.

I have a VFD running my mill but I was curious about running a 3 phase welder and other 3 phase equipment. I know a VFD won't run a welder, and around here you can get a couple of welders cheap that run on 3 phase.

Rob :)

Arcane
10-29-2014, 08:58 PM
Thanks Guys,

I appreciate the information and feedback.

I have a VFD running my mill but I was curious about running a 3 phase welder and other 3 phase equipment. I know a VFD won't run a welder, and around here you can get a couple of welders cheap that run on 3 phase.

Rob :)

There's an interesting thread on converting three phase welders to single phase at http://www.smokstak.com/forum/showthread.php?t=97492&highlight=phase+welders

sch
10-29-2014, 11:37 PM
The Haas-Kamp conversion of 3ph welder to run on 1ph power. Multiple discussions of this on Practical Machinist dot com, some referenced in the above forum,
or just google Haas-Kamp conversion. Lots of how to and pix, makes it easy.

ironmonger
10-30-2014, 09:25 AM
A static phase converter is pathetic in comparison to just about any other method- it's just a three phase motor starter, then the motor runs poorly on single phase. Advantage- dirt cheap. Disadvantage - maybe you can get 50% of the rated motor power before overload (not the 66% touted...).

A Phase Perfect produces utility quality power, and is close to bullet proof. Many is use around here. As I said in my prior post, I have a 10hp version (guaranteed to start and run a10 hp motor) or 36 amps continuous at 240 volts delta. Dead easy to install, then forget it. About $2500-2900 in the USA for that version. Expensive, but a steal for what you get.

There are rotary's, which are statics with a 'smoothing' idler motor connected.
see:
http://www.americanrotary.com/products/phase-converters?utm_source=Bing&utm_medium=cpc&utm_term=phase%20converter&utm_content=Huge-Variety&utm_campaign=Search-March-2013


phase technologies. who make the phase perfect, is a digital 3 phase device like a vfd without the vf
see:
http://www.phaseperfect.com/
I would be remiss if I didnít link to this:
http://forums.dealofday.com/threads/265431-DON-T-BUY-FROM-PHASEPERFECT-COM-Phase-Perfect-lacks-support-and-integrity

If you want/need true 3 phase power you will need an utility connection or a motor generator set if you donít want to use a vfd.

If it's welders you need, most 3 phase inverter welders will work at somewhat reduced capacity on single phase or see this thread for more possibilities:
http://www.smokstak.com/forum/showthread.php?t=97492

FWIW, my shop is to small to bother with a 300 amp transformer machine. I have a used XMT305 and a used 200SD that occupy less space than the rotary converter to power a 300 amp boat anchor transformer machine would take. just me...

For more ideas read this:
https://dl.dropboxusercontent.com/u/37105624/Alternator%20secrets/Alternator_Secrets.pdf

I thought the section on using a 3 phase motor as an alternator/generator was interesting. I have never tried it but it is on the bucket list. :>)

paul

lakeside53
10-30-2014, 11:54 AM
A static converter is just a motor starter. On an RPC it's starting the motor used for the idler; without an idler it's starting your motor. RPC idlers need someway to get started - typically either pony motor, pull rope or static converter. "Smoothing idler" is just marking speak. A static converter is single phase, and an rpc produces 3 phase. There are some uncommon (and expensive) statics that try to produce a 3rd leg phase shift with L&C, but need to be tuned to fixed load and still require derating.

A Phase prefect is not just "a vfd without the vf". It produces TRUE 3 phase power typically with better balance than utility generation.

MaxHeadRoom
10-30-2014, 12:22 PM
Phase Perfect by their own admission, state that the 1ph 240v is passed directly though the convertor as it is in a RPC, only the 3rd phase is created digitally.
Max.

ironmonger
10-30-2014, 01:26 PM
<<snip>>
A Phase prefect is not just "a vfd without the vf". It produces TRUE 3 phase power typically with better balance than utility generation.

I agree, and you will note that the quote from there web page:

"We provide detailed specifications on digital converter performance, and all our Phase Perfect converters are ETL listed (http://etlwhidirectory.etlsemko.com//WebClients/ITS/DLP/products.nsf/vwSearch?SearchView&Query=FIELD%20ListHead%20contains%20phase%20techno logies&SearchOrder=1&SearchMax=1000&SearchWV=FALSE&SearchThesaurus=FALSE&SearchFuzzy=FALSE). You can be assured that a Phase Perfect digital phase converter will deliver performance that matches the published specifications. Simply match the nameplate specifications of your 3-phase equipment to the HP rating or the output current of a Phase Perfect."

refers to the digital phase converter... it is an inverter, just like a vfd but without the variable part. I should have said FD without the V... mea culpa.

The over arching bit is that the only way to get the perfect phase angles on three phase is with an electronic device. ie inverter, or a three phase alternator driven by what ever... anything else is an approximation.

That is not to say that the other methods are not useful or practical, just that they will not deliver true three phase power over their entire output range without tweaking. As electronics gets cheaper and cheaper the electromechanical stuff will become impractical except for every large units. As the power levels increase the industrial application of the single frequency inverters becomes less attractive. I installed a cheap Chinese VFD on my Harrsion lathe project, less than $150 bucks IIRC and the only bit making noise is the lathe and the tiny cooling fan in the VFD. This is my third VFD. I'm not going back.

paul

Alistair Hosie
10-30-2014, 02:27 PM
I have a rotary and a static converted to rotary and several (three in total believe )vfd's.I am not an expert but if it works I will use it it does not have to be perfect three phase so long as it is not dangerous to anyone or machine.I prefer to use vfd's, but this is not always practical or accepted by all machines. For example as my Smart and Brown variable speed lathe does not work with anything but a rotary convertor.Because of this,it is the one I use for my machine shop. That is apart from a vfd at my mill to save changing gears and speed control. Happy Al, LOL .have safe fun Brothers.

lakeside53
10-30-2014, 06:17 PM
Phase Perfect by their own admission, state that the 1ph 240v is passed directly though the convertor as it is in a RPC, only the 3rd phase is created digitally.
Max.

Yes... but that is all you need to create true 3 phase. After the L3 digital portion (continuously adjusting the voltage and current for unity power factor at the correct phase relationships) there is a lot of iron core(s). If you put a scope on it, there no sign of any digital artifacts. They match the incoming single phase voltage and frequency to produce the third leg that when referenced to L1/L2 produces L1-L3, L2-L3. Unlike a vfd, the device is bidirectional so regenerative energy simply passes back to the utility, and, the Phase Perfect presents close to unity power factor to the utility irrespective of the load.

I'm still amazed that there seem to be no competing similar devices. Heck, China has copied everything else.

J Tiers
10-31-2014, 12:17 AM
The phase perfect simply makes the L3 output correspond to the other two. No issue there. And it can pass energy back to the incoming line, which an RPC can do, since it is bidirectional as well.

In fact, the ordinary VFD is ALSO bidirectional. When you use the speed control to turn down the speed, the VFD returns power from the motor to the DC bus. It is the diodes in the power supply that prevent the regular VFD from being bidirectional. The "system drive" type of VFD can pass excess power right back to the line, since that type uses a second VFD section as a bidirectional rectifier stage.

The Phase perfect does the same thing, "inverting" excess DC power back onto the incoming line as AC power when required to, and rectifying power onto the bus when driving the load. The exact control method used is one which operates as a power factor correction stage, so the incoming power is effectively used.

The standard RPC also produces good properly phased 3 phase output. The issue with an RPC is that some impedance is presented in the L3 output which is not in eries with the other two. If those other two had the proper inductance and resistance added in series with them, the RPC would act the same as a 3 phase generator at all loads. A 3phase generator has an R-L impedance in series with each output inherently, so the voltage may drop, but the phasing will not change, despite loading.

Many large wind turbines have been made with "induction generators", which are essentially a slightly modified induction motor. They work well, and the main reason for newer inverter based wind turbines is the ability to get the power out without closely controlling the blade assembly rpm. The inverter de-couples blade rpm from output frequency, potentially even allowing the elimination of the expensive gearbox, as well as simplifying or eliminating the complex blade pitch system used for rpm control.

The basic induction generator is much the same idea as used in the RPC, utilizing the back EMF of the motor to provide output power.

oldtiffie
10-31-2014, 01:02 AM
If I needed 3-phase as well as my 2/1phase 50~ 230v AC I'd buy a genset - diesel preferred and - keep my AC supply as is as I'd always have a power supply if the "mains" 230v AC "fell over".

I have 2 "Honda" 230v 1phase 50~ gensets and they work very well.

mike4
10-31-2014, 04:06 AM
Yes , oldtiffie , that is why I would prefer to have at least one Diesel genset for the same reason .

Many here dont seem to take onboard the fact that the mains supply is not reliable during the current storm season.

I prefer to be working than sitting in the dark dreaming of what you could be doing.
Michael