phase converter for garage

S

Stevenfyeager

Senior Member
Location
United States, Indiana
Occupation
electrical contractor
a friend wants to buy a 3 phase planer (don't know yet the voltage or amps, it will be purchased at an auction) for his single phase garage (100 amps)
Do you have any approximate cost or what it involves installing a phase converter ? I have not done one. Thank you !
 
American Rotary is a good place to look for an RPC. You can input your voltage and needed amperage for your loads into their calculator and it will tell you the recommended RPC.
 
Thank you all. My friend says the on line auction ends today. I don't think I can learn enough quickly enough for him. It sounds like it may cost him $300 or more to buy a device that will allow him to use this planer. He was going to try and find out the voltage, amperage, but I don't know if he has yet.
 
electrofelon said:
Unless it needs a particular odd framed motor for mounting, I would just change the motor to single phase.
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This. Unless he plans to buy lots of 3 phase tools in the future.

My now deceased brother was into all sorts of odd wood working tools. He picked up several 3 phase things at auctions or shop closing sales. He died with all of them collecting rust in the corner of his shop, never used.
 
I hooked up one for a customer a few years back for a 3ph planer. He later got another machine that needed 3ph and wanted it connected. I wired both machines to a two position switch so he could choose which machine to run. He didn't ever need to run both at once.
 
Seven-Delta-FortyOne said:
It will be more than $300 for an RPC, 3 phase panel, 3 phase breaker, wiring, appropriate receptacle, and installation.
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For a single piece of equipment, why would you need a 3ph panel and breaker? As long as the motors (machine and idling) are properly protected, I don't see the need for a 3ph panel or breaker. If something faults, or shorts, the single phase breaker would trip. The mfg/3rd leg would also be dead.
 
Seven-Delta-FortyOne said:
It will be more than $300 for an RPC, 3 phase panel, 3 phase breaker, wiring, appropriate receptacle, and installation.
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If you want to do things right and proper it will probably be more expensive than the planer itself.

I had a housemate who ran a 3 phase lathe using a surplus 3 phase induction motor as the RPC. He'd power things up, manually get the shaft spinning, and then start the lathe. If the initial spin of the shaft was the wrong way, everything would run in reverse.

Tools that have lots of inertia but not lots of friction can be left to spin, and they act as RPCs for the rest of the shop. If you want to see how people can get creative with rotary phase conversion, this is an oldie but a goodie: https://www.electrical-contractor.n...28477/all/using_old_motor_to_transform_2.html
 
Little Bill said:
For a single piece of equipment, why would you need a 3ph panel and breaker? As long as the motors (machine and idling) are properly protected, I don't see the need for a 3ph panel or breaker. If something faults, or shorts, the single phase breaker would trip. The mfg/3rd leg would also be dead.
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Guess you wouldn’t. Haven’t done one for a minute, but last one I installed a panel so they could use multiple tools.

I guess if the single phase breaker is sized to protect the machine, it wouldn’t matter how much the RPC could produce?
 
I been working with rotary phase converters more in the past year for some reason than I have my entire career.

A rotary phase converter has the advantage of being able to independently run multiple motors where a VFD can only run one at a time or if running multiple motors they must all be started, stopped, accelerated, decelerated all together and will be all running at same frequency if you pick some intermediate frequency to run the drive at.

The "idler motor" will typically need to be about twice the rating of the largest motor you will be starting. If you purchase a phase converter unit their selection information will determine which unit is needed, but still basically works out to the idler motor is about twice the rating of largest motor to be run. Total capacity you can run can be rather close to rating of the idler motor if they are all smaller than half the size of the idler.

Center pivot irrigation machines are one common application where I am to use rotary phase converters. They often have an idler motor that is maybe in the 7.5 HP range, it is running the center pivot that may have anywhere from 6 to 12 motors all rated anywhere from 1/3 to 3/4 hP being pretty typical. They seldom all run at one time but can be times where quite a few are running simultaneously for a short time.

If you have a three phase motor that is twice the size what you wish to run you can build a phase converter with it and some capacitors. Larger sized might need some "start capacitors" and a potential relay to switch the start capacitors out once the thing has accelerated. Or you can like someone else mentioned give it a spin to get it started.

Since you basically need a idler motor twice the size of largest motor to be powered, you can get somewhat of a rough idea of cost if you know how much a three phase motor the size of the needed idler will cost, and figure it will be at least that much plus some additional items.

If the planer is say two or three HP you might want to consider a phase converter that will handle at least a 5 HP or even 7.5 HP load just so that when he decides to purchase some other three phase machine maybe it can still handle it. Or he may be upgrading when he does purchase those items.
 
ActionDave said:
I agree with swapping the motor. Its rare that it can't be done and makes life better.
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My luck with that kind of machinery is it always has some OEM motor that you can't just replace with a general purpose motor. Could be possible however to get an OEM single phase motor for that machine from the manufacturer in some cases.

A guy I put together a roto phase for last winter had a couple milling machines that were ancient with OEM motors that were not going to be easy to replace. Plus he was a farmer and wanted to be able to test his irrigation fertilizer pumps by running them off same phase converter, which meant 480 volts would be preferred, but the milling machines were dual voltage so it worked out. Then he bought a three phase lathe. That motor was two speed and 240 volts only. Couldn't run off the 480 roto phase. I ended up using a VFD on it and connecting the motor in the high speed configuration and used the existing switches for speed and direction changes to signal the drive for speed and direction. IIRC that motor was OEM type motor as well and would have been somewhat difficult to find a single phase general purpose motor to replace with let alone get two speeds out of it.
 
Well, my friend said the planer sold for $548 today which was more than what he wanted to pay plus converter costs I was showing him.
But thank you all. I spoke with two of my elec contractor friends here and they had never done this either. (one is just now in the process of first time learning about it for one of his customers.)
 
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