rotary converter question

[glennster]

this is about rotary phase converters, not about VFD’s. i see some you tube stuff on building a rotary phase converter using a 3 phase motor to get 3 phase power from a single phase. so, i have some used but still good 10 hp 3 phase motors from the spray booth at my body shop. they are sealed and draw about 25 amp. so here is the question. if you have a 100 amp single phase panel, and you use this motor for the phase converter, what is the maximum amperage that you can produce on the 3 phase output? btw, i have 600 amp 3 phase at the shop, so no, i am not building a converter.

 

[Butch(OH)]

Remember that the convertor does not make any power, it's converting. Thus input watts and output are the same less losses. 1 HP is 746 watts. A 10HP motor is 7460 watts. 7460/ 240 volts=31 amps, these reflect full loading, less load equals less amps. Using that same equation to answer your question 100 amp x 240 volts = 24000 watts. Divided by 746 is about 32 HP These numbers reflect 100% efficiency which is not real life. There is much home made convertor info on the web. I have had a Rotophase in my shop for over 20 years but also had a homemade unit at another location to run one machine. I used a cheap static convertor to start a idler motor as you suggest. It worked perfectly without any added capacitors.

 

[leroy in ne]

Some one told me you should derate motor size by 1/3 for full load capacity if using a converter. In other words do not put over a 6 1/2 horse load on a 10 horse motor. Experts advise appreciated for confirmation. Leroy

 

[timcasbolt]

Some one told me you should derate motor size by 1/3 for full load capacity if using a converter. In other words do not put over a 6 1/2 horse load on a 10 horse motor. Experts advise appreciated for confirmation. Leroy

That would apply to a static phase convertor. My first phase convertor was a phase-a-matic on a 1 1/2 hp Bridgeport. In theory that gave me about 1 hp. I used the instructions that came with the convertor to wire in an idler motor and increased the hp to >95%.

 

[cleddy]

That would apply to a static phase convertor. My first phase convertor was a phase-a-matic on a 1 1/2 hp Bridgeport. In theory that gave me about 1 hp. I used the instructions that came with the convertor to wire in an idler motor and increased the hp to >95%.

I have some practice building Rotary phase converters by using a small single phase motor to get it running up to speed and than turning the 3 phase converter motor on. I have a 15 Hp unit that will start a 5Hp Lathe and a 10Hp Air Compressor 3-phase motors plus 4 more but maybe not at all the same time. I have a 5hp direct drive Campbell-Hausfelt Air Compressor I can not get to start at all. I bought the CH compressor where there was 3-Phase power so know it works but now would like it operational so I can sell it. It going to be hard to sell if a potential buyer can't see it works. Any ideas on how to get this CH Compressor to run-Changing motors doesn't seem to be an option? Thanks in advance.Cleddy

 

[buickanddeere]

Yes I know this is about rotary converters . But why mess with a rotary ??? This is 2024 not 1950.

 

[Ultradog MN]

Yes I know this is about rotary converters . But why mess with a rotary ??? This is 2024 not 1950.

Well for one reason you can run several machines with one RPC.
Not all at the same time of course but in a 1 man garage one or two at the same time is enough.
Example: Drilling, grinding or deburring while the band saw is making long cuts - on a converter that cost about $200 to build.

 

[timcasbolt]

On a rotary phase convertor you can run all your machines at once. I run a Bridgeport, band saw, and a surface grinder at the same time.

 

[buickanddeere]

On a rotary phase convertor you can run all your machines at once. I run a Bridgeport, band saw, and a surface grinder at the same time.

No reason why a VFD can not operate all that equipment at the same time

 

[zuhnc]

One needs a VFD for each machine. The VFD is a Variable Frequency Drive, meant to vary speed of only one motor. And, it has to be matched to the equipment is powering.

A Rotary Converter produces 3-phase from single phase, and does not vary frequency. Produces power similar (not the same as) commercial 3-phase power. I built one for about $50.00 to run my Millrite mill. Since I don't have a VFD connected to it, I still have to change the belt on the pulley for different speeds.

A 20 HP rotary converter can power quite a bit of low HP equipment, relatively cheaply. A VFD to power 20 HP worth of equipment is quite pricey, if you can even find one. zuhnc

 

[Watthour]

Actually, decent industrial VFDs can operate multiple motors, are rated for that, and have explicit instructions on parameter settings for that application. ABBs ACS series, Allen-Bradley PowerFlex, and some Mitsubishi drives can handle it. I suppose there might be some low-end, off-brand types that can do it also, but those are usually doorstops in my realm.

 

[cleddy]

One needs a VFD for each machine. The VFD is a Variable Frequency Drive, meant to vary speed of only one motor. And, it has to be matched to the equipment is powering.

A Rotary Converter produces 3-phase from single phase, and does not vary frequency. Produces power similar (not the same as) commercial 3-phase power. I built one for about $50.00 to run my Millrite mill. Since I don't have a VFD connected to it, I still have to change the belt on the pulley for different speeds.

A 20 HP rotary converter can power quite a bit of low HP equipment, relatively cheaply. A VFD to power 20 HP worth of equipment is quite pricey, if you can even find one. zuhnc

I bought a Name brand VFD (Woods) several years ago for quite a bit of money ($500.00+) to run a step-pulley Bridgeport mill hoping to get Variable speed and run 3-phase on single phase 120 volt cord. It worked fine in all regards except quickly reversing motor when tapping. Had to come to stop and then reverse. The unit was stored for several years in a box it tool cabinient and when I wanted to use it would not work. Tech guys looked at it and could not get anything out of it and Woods company has long moved on from that technology. I got a little informational booklet on how to build Rotary phase converters and built 2-10 hp, 1-15 hp and a little 5Hp to run the Bridgeport mill. They have all worked fine except for charging a electric forklift and my CH direct drive air compressor. If I knew how to balance the power legs out I think they would work even better???? When I checked one time the cost to run 3 phase 2 miles to my farm was $30000.00 or more???

 

[timcasbolt]

I bought a Name brand VFD (Woods) several years ago for quite a bit of money ($500.00+) to run a step-pulley Bridgeport mill hoping to get Variable speed and run 3-phase on single phase 120 volt cord. It worked fine in all regards except quickly reversing motor when tapping. Had to come to stop and then reverse. The unit was stored for several years in a box it tool cabinient and when I wanted to use it would not work. Tech guys looked at it and could not get anything out of it and Woods company has long moved on from that technology. I got a little informational booklet on how to build Rotary phase converters and built 2-10 hp, 1-15 hp and a little 5Hp to run the Bridgeport mill. They have all worked fine except for charging a electric forklift and my CH direct drive air compressor. If I knew how to balance the power legs out I think they would work even better???? When I checked one time the cost to run 3 phase 2 miles to my farm was $30000.00 or more???

I ruined two phase a matics power reversing. Then I bought a Cedarberg.

 

[glennster]

Yes I know this is about rotary converters . But why mess with a rotary ??? This is 2024 not 1950.

yup i knew somebody would have to bring up vfds. not what this post is about. if you notice my original post i have 600 amp 3 ph at the shop.

 

[glennster]

Yes I know this is about rotary converters . But why mess with a rotary ??? This is 2024 not 1950.

instead of messing with a vfd, just call your power company and have a 3 phase drop put in. easy peasy.