Rotary Phase Converter

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Model T Ford Forum: Forum 2005: Rotary Phase Converter
Top of pagePrevious messageNext messageBottom of page Link to this message  By Chris Dailledouze on Wednesday, February 06, 2008 - 01:12 am:

I have a milling machine that I want to use. My home is wired for 220 single phase and will need a phase converter to utilize the machine which requires 220 3 phase.

Does anyone have plans for building a ROTARY phase converter? They do not look that complicated and at $2000.00 out of a catalog I am thinking I can build one a lot cheaper.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Paul Mikeska on Wednesday, February 06, 2008 - 01:18 am:

Chris,

They are fairly easy to make. Google "phase converter" and you will find plans and formulas to build rotary and static phase converters. Basically you will need another 3 phase motor as an idler and it will power your mills motor.

Good luck

Paul


Top of pagePrevious messageNext messageBottom of page Link to this message  By Paul Mikeska on Wednesday, February 06, 2008 - 01:23 am:

Chris,

Give this a try. http://www.metalwebnews.com/howto/phase-converter/phase-converter.html

Paul


Top of pagePrevious messageNext messageBottom of page Link to this message  By Chris Dailledouze on Wednesday, February 06, 2008 - 01:39 am:

Paul wow... thanks.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ken Kopsky on Wednesday, February 06, 2008 - 01:51 am:

For about 1/10 the price of an RPC you can get a VFD (Variable Frequency Drive) that will convert single phase 240 to 3-phase and give you variable speed as well as other benefits. Unless you're into the 7hp and up range on equipment, an RPC carries few cost benefits. One definite benefit is that you can use an RPC to power multiple machines. Not likely that an individual will be running multiple machines at once, but RPC's are more forgiving on overload.

Forget the static phase converters unless you can live with it's shortcomings. They give you 3-phase on start up only then drop back to single phase. At that point, you loose 1/3 of your motor power. (3hp becomes 2hp, etc.) You also loose the smoothness of the 3-phase motor.

Automation Direct carries a good line of VFD's at great prices.
http://web1.automationdirect.com/adc/Home/Home


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jim Weir on Wednesday, February 06, 2008 - 01:54 am:

Agree 100% with Ken !

Sincerely

Jim Weir


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ivan Jorgensen on Wednesday, February 06, 2008 - 02:33 am:

Or just replace the motor with a 208/230 single phase motor.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ray Elkins on Wednesday, February 06, 2008 - 05:38 am:

Hard to do Ivan. Most mills, Bridgeport-style anyway, have a motor that is their design and there are no replacements in single-phase. Many vendors sell converters in the $400 range. Heres 2 on Ebay
http://cgi.ebay.com/Bridgeport-3HP-Rotary-Phase-Converter_W0QQitemZ270209153924Q QihZ017QQcategoryZ41952QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
And another
http://cgi.ebay.com/New-3HP-ROTARY-PHASE-CONVERTER-Bridgeport-Milltronics_W0QQit emZ250212893326QQihZ015QQcategoryZ41952QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

Here is a search on Ebay for VFD's. I'm with Ken on this one. I like Allen-Bradleys personally, but most any brand are excellent and you won't believe all the fun stuff you can do with them!

http://search.ebay.com/search/search.dll?sofocus=unknown&sbrftog=1&dfsp=1&from=R 10&_trksid=m37&satitle=variable+frequency+drive&sacat=-1%26catref%3DC6&sargn=-1% 26saslc%3D2&sadis=200&fpos=42071&sabfmts=1&saobfmts=insif&ftrt=1&ftrv=1&saprclo= &saprchi=&fsop=1%26fsoo%3D1


Top of pagePrevious messageNext messageBottom of page Link to this message  By John McGinnis on Wednesday, February 06, 2008 - 09:52 am:

Just make a capacitor start motor out of the three phase by adding a starting capacitor to the unconnected winding. This is shown in one of the previous links. Replace the pushbutton with a current sensing relay in the primary winding which will switch out when the motor gets started (use a standard motor start relay). I have used many three phase motors this way and they work well...even for heavy start applications such as a compressor.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ken Ward on Wednesday, February 06, 2008 - 10:17 am:

I have used a static unit for years on my Van Norman mill. No problem.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Michael K Johnson on Wednesday, February 06, 2008 - 10:26 am:

If you go for a static phase converter you could have problems when reversing the motor when turning or milling threads. This is the advantage of three phase. Instant reverse without damaging the motor. Does anyone have experience with the low end static products and certain operations like threading? The could be adequate for the garage applications.

I bought a phas-a-matic rotory that has been excellent and is hooked up to the mill, lathe and surface grinder. Rarely are they used at the same time but I've had all three going with one under load.

Used to work for a industrial controls company Yaskawa Electric which have excellent VFD drives but they are pricey and maybe overkill with about 150 parameters.

Wish I would have made a rotary but the internet wasn't so helpful with plans at that time.

Thanks for posting. I hope you will give us progress reports if you "do it yourself".


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Cascisa in Poulsbo, WA on Wednesday, February 06, 2008 - 11:01 am:

I will add my vote for a VFD (Variable Frequency Drive). There are a lot of benifits over a RPC (Rotory Phase Converter). Just remember - If you use a VFD with a single phase source you must derate it by 50%. Use a 2 HP VFD to run a 1 HP motor.

Be_Zero_Be


Top of pagePrevious messageNext messageBottom of page Link to this message  By kuhner on Wednesday, February 06, 2008 - 11:15 am:

Go to this group. Its from the Machinist Forum. They have several plans available here for RPCs.
http://www.practicalmachinist.com/vb/forumdisplay.php?f=11

kuhner


Top of pagePrevious messageNext messageBottom of page Link to this message  By Chris Dailledouze on Wednesday, February 06, 2008 - 01:26 pm:

Hmmmm ever heard of a VFD, they are certainly cheaper than a RPC. But I do now have a question. While I am getting (some type) of converter for a Mill (1.5HP 4.2 Amps) I am hunting for a lathe of and around the size of 14 x 60, many (some) have upwards to 10 HP motors.

With that said... am I reading some of this info correctly? If I do plan a converter(VFD)for 10 HP I need to buy one for 20 HP? If so the cost savings is getting closer to a wash on a RPC?

Would the smae apply to a RPC re HP needs?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Chris Dailledouze on Wednesday, February 06, 2008 - 01:30 pm:

So any EE's in the Dallas area needing a converter such as myself. I'll buy the beer and parts if I can use your brain... :-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Chris Dailledouze on Wednesday, February 06, 2008 - 01:31 pm:

So any EE's or other skilled electrical types in the Dallas area needing a converter such as myself. I'll buy the beer and parts if I can use your brain... :-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kelly Lehr on Wednesday, February 06, 2008 - 02:16 pm:

Hello!
We run static phase converters on 2 mills. A Jet 10x54 and a Supermax 9x49. Both are full size machines running on 220v/1ph primary and going to 220v/3ph via. static converter. Both machines are variable drive (not step pulley).Keep in mind the
3ph from the converter is only used to start the motor and is not used once the motor is running.We have had no problems with the static converters including reversing.Manual machines are no problem,but CNC machines will not run on a converter. The last converter we purchased was from americanrotary.com 1-888-743-6832 about $120 for the converter. Call them, they will answer any questions and size the unit to your machine. I am not promoting this company, simply telling you that I solved the same problem you have by using their advise and converter. Very cost efficient also.
Good Luck......Kelly Lehr Yankton,SD


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jim McDermaid on Thursday, February 07, 2008 - 04:14 pm:

I had a friend who ran his three pahse machine shop for years using a junk three phase motor as a phase converter.

He had it lashed up so a junk yard single phase motor got the junky three phase motor up to speed and then the three phase motor provided the missing phase. Once it was spinning the single phase motor wasn't needed.

It seemed like the more motors he had going the better it worked.

I don't recall any capacitors in the system just the big old three phase motor in the corner.

The guy had no electrical skills either.

Jim


Top of pagePrevious messageNext messageBottom of page Link to this message  By John McGinnis on Thursday, February 07, 2008 - 05:33 pm:

Running the risk of repeating myself... for the application that started this thread, there is no need for a rotary converter, variable frequency inverter.....just a simple motor starting capacitor and a motor starting relay obtainable from a junk washing machine. Keep it simple, all for $20.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Cap Weir on Monday, February 11, 2008 - 01:01 am:

Chris. One more 2 cents worth
You can not run a single phase motor on just two leads and get any useable power out of it! <<caution..>> Three phase motors need a 'Set of Three wires' that have a 'Phase' relation to each other of, 120 deg. ( Thats 360 / 3 ) It's the 'Pull' of the rotor to the three sets of wire coils, that causes the shaft to spin!. If one wire is missing, there are two coils that do not have power, and the motor does not 'Know' which direction to spin. In that case the motor is now a 'Toaster' and will act as such and produce smoke!.
The problem with house power is, It is derived from 1/3 of the three phase power that was used to produce it!.. And it has only two wires that send power back and fourth to each other. In math terms it's 180 deg phase shift. If you hook up a three phase motor to a set of two wires, you will have the one coil that is hooked between wire 1 and wire 2 energizing but the coil that is between wire 2 and wire 3 is not getting any power or the coil that is between wire 3 and wire 1 is also not getting power. We somehow need to get power over to wire # 3. If we just hook up wire #3 to wire #2, we have it powered, but all the powering is happening at the same time and nothing moves!. So we need to 'Shift' the voltage on the 'Third leg' to have it happen at a later time. This is where the Capacitor comes in. If we take a Capacitor and hook it from the second and the third leg of the motor ( with the main lines connected to leads one and two) the capacitor will charge from the second lead and as the second lead looses voltage ( on the down hill fall of the line cycles ) it will 'Dump' it's charge to the third leg. This causes a 'Phase Shift' that is needed for the motor to 'Know' which way to turn. In actually the motor is designed to have a 120 phase shift, and we are giving it a 90 deg phase shift, but it will turn and run.
The 'Size' of the capacitor ( in Mf ) and the Speed of the motor all have relation to how much power that can be produced. To start the motor, we have a problem, as we have no speed!. To get the thing moving we need to have a BIG ( inMf) Cap. This big starting capacitor is only used for a very short time. Because ALL the power that 'Drives' the third leg must be stored then supplied by the capacitor, they need to handle a lot of heat. To counter this 'Large Start Cap Problem' there is a series of Capacitors called 'Start Caps'. These units can handle a large amount of power, but only for a short time ( a few seconds ) or they will pop!.
An other series of capacitors is called 'Motor Run Caps'. These units are a 100 percent duty cycle and are a wet filled metal can. these will be used to shift the power during the run of the motor.
To put together a useable single to three phase converter, we gotta put it into a box.. Plastic is really nice, as the sparks do not reach out and byte ya. and some cap values would be nice.. From practice I have found that using a Capacitor of 25Mf per motor Hp for the run cap works very well. The temporally installed motor start Cap must be about 10 times the motor run cap.. ( 250 mf per hp for start cap ) and Switching all of this can get trickey!. The easy way to do this is to not use a start cap set up and install the run cap on a 'Pony Motor'. this can be any motor that does not have a large start load. My 'Pony Motor' is my 12" disc plate grinder. This is the motor that I start before I start my lathe!. The lathe is a 3 hp and the grinder is a 1 hp and I am using a 50 Mf cap for the set. When I start the grinder, it kinda growls then slowley gets up to speed. Then I start lathe and they all are happy. I have put together a Start Cap box from a 'Cap Assist Kit' as sold by GRAINGERS for use on hard start single phase heat pumps and air conditioners. It works well, but on the 3 hp lathe it does not stay engaged long enough.. and I get relay chatter. I've done all the voltage checks and figured out how to fix it by using a different start relay ( also by GRAINGER) but I have a Scheme that works, so I'm staying with it.
I first started running my maching shop stuff off of single phase about in '78 or so.. and the machinery likes the 3 better than single, but at various times through history I have had to resort to the cap bank. This last time started in December when I have to move my machine shop back into my Barn... Then the machines looked at me and said 'Not Again!##@' I have never burned up a three phase motor by running it on these converters that I have built, but I have blown up cap banks by not getting the start relay to let go, and made a bunch of toxic smelling stuff!!.. Yes GRAINGERS also sells Motor Run Caps.. any voltage above 240 vac is ok.. 380 or 440 is OK.. With caps.. don't go lower voltage than you need.. Oh.. Don't forget the fuses!! Cap


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