# 15 HP Rotary Phase Converter



## rock_breaker (Nov 6, 2011)

I was given a 15 HP 3 phase 440 Volt motor that has just been lying around for several years. If I were to try making a phase converter out of it what size capacitor would be required?


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## Starlight Tools (Nov 6, 2011)

Let's start with the first hitch.  Is the motor a 220/440 or just 440.  You need the single phase voltage correct before you can get the proper voltage out, so you will want to start by making sure you can feed the motor with the right voltage for it.

if you google fitch williams there will be a variety of circuuit diagrams that will show up on hashing together RPC's, including one in the 15 HP range.

Walter


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## rock_breaker (Nov 7, 2011)

starlight_tools said:


> Let's start with the first hitch.  Is the motor a 220/440 or just 440.  You need the single phase voltage correct before you can get the proper voltage out, so you will want to start by making sure you can feed the motor with the right voltage for it.
> 
> if you google fitch williams there will be a variety of circuuit diagrams that will show up on hashing together RPC's, including one in the 15 HP range.
> 
> Walter



Thank you for the  information, I will check the name plate today.
The sketch and information on the fitch williams site is well presented and if I do have a 220/440 motor it is obvious that a pony motor will be required.

Thanks again

Ray


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## Starlight Tools (Nov 7, 2011)

Ray

There are a number of posts on this site, and my views on RPC's come through very clear.  Building a RPC is not a simple task and definitly not for somebody that does not have electrical common sense.  The big problem with the circuits presented by Fitch Williams, et al, is that they often leave out many of the safety and fail safes that are required for the RPC to run properly and safely.

This can and will negate any form of fire insurance if they are not built to code and stamped as such! CSA, UL, ULC, etc depending on which country you are operating in.

I used to make RPC's but now I deal with a company that speciallizes in making them.  www.electram.com  and have become a dealer for their products.

If you choose to build your own, then be watchful of wire sizing and proper wiring technique, but propably the most important is to make sure you have a magnetic starting switch that will prevent the unit from trying to restart after a power outage.  Most of these units require some method of getting the pony motor or generator motor started.  A bank of start capacitors and some form of switch.  The fancy ones have a relay type switch and will start on their own, but most, if not all of the RPC's have a manual start switch.  This switch brings the bank of start capacitors into the circuit just long enough to get the generator motor running.  It must be only momentary contact.  But, if the power gets restarted, without that switch being on the unit tries to start, but the motor does not turn and it sits there single phasing until the magic smoke is released.  the other route is to leave out the starting capacitors, and spin the generator motor with either a rope pull start, or a secondary single phase motor that can be powered up just long enough to get the generator motor spinning.

Also be careful that any machines that run off the RPC, can not be ever single phased either, results, more magic smoke escaping!

For this reason, I try to make sure that any RPC I supply has the proper start up sequencing buitlt in. on the PhaseMAXX units I sell from Electram, when the start switch is pressed, only then will power be introduced to the generator motor, and it automaticaly starts from there.  If the power is interupted, the whole RPC shuts down until the on switch is depressed.  Also I have them made with  TLC, Timing Line Contactor.  As the Black and Red wires from the single phase 220V continue right from the single phase breaker box, straight through to the load motor, it is normal to have the load motor only partially energized, IE single phased.  This is a bad condition that is not safe for the motors, if they get switched on.  To avoid this there are two usuall methods.  If the magnetic switches to the load are tied into the RPC, such that they can only be energized if the RPC is running.  This requires wiring from each Mag switch back to the RPC and is a pain in the butt, IMO.  The Preverential method is to use a TLC.  This is a Magnetic switch capable of carrying the full load of the RPC that is wired in between the RPC and the load motors.  If there is no three phase power from the RPC then the TLC stays off and there is no possiblility of having any voltage further down the line.  Once the RPC is on and producing three phase power the coil for the TLC is energized and now we know that full power is being transmitted to the load motors.

Also an issue is voltage stability.  If you are only running a large motor that is close to the maximum HP rating of the RPC, then not usually a problem, but if you will be running a variety of motors, the you need to have a VLC Voltage Level Control, or Voltage regulator installed.  That way whether the load motor is 15 HP or 1/3 HP it will run without being damaged.

Larger RPC's tend to brown out the neighbourhood getting them started, so a soft start feature is a fantastic way to help prevent this.

Finally, the generator motor, from a properly designed RPC, is not just a "salvaged three phase motor with its shaft cut off"  They have specially designed rotors that will make sure that the three phase power  being produced is as good or better than the power that the utility company can provide.

Walter


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## rock_breaker (Nov 9, 2011)

Thanks for the additional information on RPC's Walter. My thoughts were to build one using this motor just to see how the motor runs, there is no bearing noise at slow speed and I believe the windings are OK. The  farmer up the road has an RPC to run the motors in his grain claeaning elevator, but I believe his unit will only run up to 7.5 HP.

After receiving your information I will probably abandon the idea of 3 phase in my shop. Just to much hassle at this late stage in life. I currenrtly have 1 lathe, a metal cutting band saw and a shop air compressor on 220VAC and can add a radial arm wood saw and a bench grinder.

Thanks again and I will keep you in mind if a real need for a RPC comes up.


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## Starlight Tools (Nov 9, 2011)

Ray


Whoa! Hold on there!

It is not my intention or advise to try to talk you out of putting three phase power into your shop. Believe me, it was one of the best investments I have made.

I am only being the voice of reason here and advising that if you go ahead and build the unit, use proper procedures and make sure you "play safe" 

Electricity can kill if used improperly, so be safe! That does not mean do not use it at all.

If you follow the Fitch Williams diagrams, you can build up a nice little RPC. Add a magnetic switch between the breaker and the RPC as a safety disconect and off you go. I built my RPC in a 3 phase load centre so that there was a space to put breakers for the different tools I would run. We powered much of a woodworking factory with that unit and it ran fantastic. The client that had me build that one, had it wired in by somebody else, and left out the Magnetic Switch. He sold the building and the new owner took over the RPC with the building. A year later, the power went out, and all the employees scrammed. Sooner or later the power came back on and the eventually one of the employees came back to do something and found the generator motor smoking away. They had the motor rewound, and put in the mag switch I had advised they do and the unit has run flawlessly ever since. 

Yes I went with a PhaseMAXX when I powered up my own shop, I put in the 7TZ which is a 7-1/2 x 22 HP unit.

Yes I am sure you can take that 15HP motor, providing it is 220V, which you already have, and make up a very suitable RPC with it, that will power up all sorts of new toys for you. Just make sure you do it safely.

In this section of the forum, you will find the wiring diagram and pictures of my Set Up if you want to see how I powered my shop. http://www.hobby-machinist.com/show...to-3-Phase-using-PhaseMAXX-7TZ-Soft-Start-RPC


Walter


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## rock_breaker (Nov 10, 2011)

Starlight_Tools

Thanks again for your advise and safety input. You are not talking me out of making a RPC, I am not sure I want to invest the time and money. To those that read this thread I would say study Walters advise and use it.  

I do have a smattering of electrical experience. My dad who taught me basic lathe operations and house wiring skills managed the local power company until he retired in 1976. I supervised a quarry for Ideal Basic Industries, now Holcim Inc. for twenty years. The rock crushing plant used 4160 volt 3 phase for the 600 HP primary crusher motor and the 900 HP secondary crusher. The conveyor motors were all 440 3 phase. The stipping shovel utilized 1500 feet of trailing cable coducting 4160 VAC also.  San Isabell Power Company loved us The power bill for the cement plant was about $400,000 monthly. Having worked around that type of voltage a person develops respect for electricity. I have worked with several proffesional electricians and know I wouldn't make a wart on theier posterior.

In my shop I keep every thing on breakers and have a preferance for 12 gage wire. I also utilized Ugly's Electrical guide.

Thanks again for the help, advise and safety input.

Ray


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## rock_breaker (Nov 14, 2011)

I get more projects without really trying as time goes by so I may not get involved. 

Isthe website for American Rotary different from their name ? I would like to see what the plug and play unit will do and what it costs.

I am in the process of rewiring my shop which is of frame construction and my in-laws former residence. It sure takes a lot of time.

Have a good day.

Ray


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## PeRock (Dec 25, 2018)

Starlight Tools said:


> Ray
> 
> 
> Whoa! Hold on there!
> ...


Hi Walter
How can I open the link you posted above?
Thanks for you consideration


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## Starlight Tools (Dec 25, 2018)

PeRock said:


> Hi Walter
> How can I open the link you posted above?
> Thanks for you consideration


Sorry not sure, that is an old link and you will have to check with the admins to see if it was even carried over when they changed servers.


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## JimDawson (Dec 25, 2018)

PeRock said:


> Hi Walter
> How can I open the link you posted above?
> Thanks for you consideration




We lost a lot of stuff in the ''Big Crash'' a few years ago.  That thread may have been one of the casualties.

There are a number of other rotary phase converter threads, or feel free to start a thread to ask questions.


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## Rick Berk (Dec 25, 2018)

I Built a  PRC 25 years ago with a 15HP Lincoln Electric motor, it requires 770 mfd to start and 440 mfd to run. Another trick I learned when I built a 40 HP RPC, I start the 15 HP first and let it start the 40 HP then shut the 15 HP off. This is for my wide belt sander only. The 15 HP runs my whole shop of Jointer, Planer, 16 inch table saws, 16" radial arm saws. with the largest motor being 7.5 HP. Hope this helps.


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## Ulma Doctor (Dec 26, 2018)

Starlight Tools said:


> Finally, the generator motor, from a properly designed RPC, is not just a "salvaged three phase motor with its shaft cut off" They have specially designed rotors that will make sure that the three phase power being produced is as good or better than the power that the utility company can provide.



can you explain the "Specially Designed Rotor" that makes power as good or better than the power company???


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## Keith Foor (Jan 6, 2019)

Ulma Doctor said:


> can you explain the "Specially Designed Rotor" that makes power as good or better than the power company???



Yes please, inquiring minds want to know!!!


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## Janderso (Feb 6, 2019)

I'm looking at this one to run my 7.5HP Clausing Colchester in my new home garage/shop.
What are your thoughts?
https://www.americanrotary.com/products/view/ad-digital-smart-series


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## JimDawson (Feb 6, 2019)

Janderso said:


> I'm looking at this one to run my 7.5HP Clausing Colchester in my new home garage/shop.
> What are your thoughts?
> https://www.americanrotary.com/products/view/ad-digital-smart-series



It should work fine.


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