# Rotary Phase question



## Wdnich (Aug 25, 2014)

I understand rotary phase power and the conversion process. All my research tells me that once installed, I can run multiple machines off it, if I purchase a large enough phase convertor. 

1. Would I wire it through the shop just like wiring another box?  Install a breaker panel, route the output from the convertor to it, then run individual wiring from breakers to machines.

That has always been my limitations in the shop is power limitation.

My garage feeds off a 100 amp from the house. 

2. Would this limit the use of the phase convertor?

3. Any special considerations to take into account?  i.e special wiring, use specific breaker panels, etc.

Thanks for any help. This Bridgeport purchase has really pushed things to the next level in the shop. I understand I can run VFD's for everything, but want to move up to a larger compressor also. The medium size 110/220 I have been running never keeps up with the usage, and it is time to go larger for my needs overall. My research on VFD has said that some compressors do not do well because of the cycling on them.

I have been told the electrical gurus on here and help me solve my dilemma and questions. I look forward to the help.


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## Rbeckett (Aug 25, 2014)

100 Amp service should be more than enough to run a phase converter as big as you would ever need.  You could run multiple machines at the same time with no problem.  I would definitely do the breaker box route after the converter to protect you and the converter from accidental damage.  The really smart guys here will have to gie you the code requirements for the proper wire gauges, but you should not have any supply problems at 100 amps from the service line to your house.  If you are tapping into your home breaker box I would also consider putting a main breaker as a sub box at your house to allow you to shut off all power to the shop from there and to protect your home from a short also.

Bob


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## ecdez (Aug 25, 2014)

I just finished installing mine a few months ago.  It was way easier than I thought it was going to be.

Here's a link to my thread.

http://www.hobby-machinist.com/showthread.php?t=23150


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## JohnG (Aug 25, 2014)

Motors that start under load like air compressors or hoists require extra starting torque and extra starting current.  If the compressor will start up by itself to maintain your air supply, be sure you size the main breaker, wiring, and convertor to start the compressor while running another machine.

I have a 7 1/2 hp convertor on a 50 amp breaker.  My 5 hp compressor can start up while I am running a 4 hp wood shaper plus a 2 hp dust collector plus a 1/2 hp feed motor.  If it starts while I am running a 3 hp engine lathe, the voltage drop causes the starter on the lathe motor to drop out.

I tried piggybacking a second 7 1/2 hp motor on the convertor for extra starting torque.  Then the lathe/compressor combination started and ran fine, but the shaper/collector/feed motor/compressor combination tripped the 50 amp breaker.


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## LJP (Aug 25, 2014)

I have 2 shops, one for metal working, one for wood working. I have been running both rotary and static converters for over 25 years without problems. I use rotary converters for multiple machines as you suggest (shaper with feeder and dust collection). The machines that I want to turn on and off all day long (table saw, band saws etc.) are on static converters. Sliding table saw is 9 HP and runs great off a static converter. Thickness planer is 7.5 HP, static as well. This way I don't need to listen to the rotary all day long. 
100 amp line is what I have as well, into each building from the main 200 amp service in the house. Never been a problem.
I do not have separate breakers after the converters, it would be nice, but I don't think you need it. 
I do have 3 phase twist lock outlets so that machines can be disconnected easily (code in Mass.)
Good Luck, Larry


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## Wdnich (Aug 26, 2014)

After reading the posts here, and further research. Pardon the illiterate electrical questions. I understand 110/220 but 3 phase is alien to me in a wiring sense.

I could convert all my garage wiring over to a three phase panel, and still run my lights and such, but have one central panel wired three phase, but running everything? If this is the case, seems like the next logical step in my shop for future usage.


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## JimDawson (Aug 27, 2014)

Wdnich said:


> After reading the posts here, and further research. Pardon the illiterate electrical questions. I understand 110/220 but 3 phase is alien to me in a wiring sense.
> 
> I could convert all my garage wiring over to a three phase panel, and still run my lights and such, but have one central panel wired three phase, but running everything? If this is the case, seems like the next logical step in my shop for future usage.




If you are planning to bring in a separate 3 phase service to your shop, then yes you can run everything off of the 3 phase panel.  Be mindful of the wild leg, about 180 V to neutral and ground.

If you are going to run your equipment with the existing service and from a RPC then I would not.  I would use the existing single phase panel to handle all of the 120/240 single phase, and then install a 3 phase sub-panel down stream of the RPC to run the 3 phase equipment.


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## psychodelicdan (Aug 27, 2014)

To add a question to the op if I may. This seems like a important thing to know and have found no info. With the RPC running off of 1ph 220 ( 2 legs powered and (generating) its own third leg which we cant be getting for free. How do we figure the amp draw of the RPC plus the machine draw to get a total? If we spin up the RPC with a pony motor to reduce the starting load how do we figure how much the RPC is using. Is the RPC getting a noticeable amp draw from the lathe/machine? Did I say that right? I'm no electrical engineer


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## Ulma Doctor (Aug 27, 2014)

psychodelicdan said:


> To add a question to the op if I may. This seems like a important thing to know and have found no info. With the RPC running off of 1ph 220 ( 2 legs powered and (generating) its own third leg which we cant be getting for free. How do we figure the amp draw of the RPC plus the machine draw to get a total? If we spin up the RPC with a pony motor to reduce the starting load how do we figure how much the RPC is using. Is the RPC getting a noticeable amp draw from the lathe/machine? Did I say that right? I'm no electrical engineer




there are mechanical losses in generating the third leg, you never get something for nothing.
you can measure the circuit draw by testing both hot lines on the single phase input. 
the total circuit draw can easily be measured there.


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## John Hasler (Aug 27, 2014)

psychodelicdan said:


> To add a question to the op if I may. This seems like a important thing to know and have found no info. With the RPC running off of 1ph 220 ( 2 legs powered and (generating) its own third leg which we cant be getting for free. How do we figure the amp draw of the RPC plus the machine draw to get a total? If we spin up the RPC with a pony motor to reduce the starting load how do we figure how much the RPC is using. Is the RPC getting a noticeable amp draw from the lathe/machine? Did I say that right? I'm no electrical engineer



All of the power comes from the 220V supply.  Total single phase power input to the converter will equal total three-phase power out plus about ten percent for losses in the converter.  There will also be some reactive current on the two-phase side.  I'm not sure how much.  Not a lot.

To figure how much current the system will draw from the 220V supply total up the power used by the loads, multiply by 1.1 to allow for converter losses, and divide by 220.


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## AlanR (Aug 27, 2014)

JimDawson said:


> If you are planning to bring in a separate 3 phase service to your shop, then yes you can run everything off of the 3 phase panel.  Be mindful of the wild leg, about 180 V to neutral and ground.


Strictly speaking not so.

Usually three phase 240V is supplied from the power company in delta configuration. Transformers within the building can be used to convert to three phase 208 volt wye which is 120V from a three phase leg to neutral. We have two such transformers in this building.

Lots of motors are rated to run at 208 volts three phase. Lots of large three phase machines have internal transformers to step down from 240V to 120V for control mechanisms.


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## John Hasler (Aug 27, 2014)

AlanR said:


> Strictly speaking not so.
> 
> Usually three phase 240V is supplied from the power company in delta configuration. Transformers within the building can be used to convert to three phase 208 volt wye which is 120V from a three phase leg to neutral. We have two such transformers in this building.
> 
> Lots of motors are rated to run at 208 volts three phase. Lots of large three phase machines have internal transformers to step down from 240V to 120V for control mechanisms.



If he uses an RPC he will have a wild leg.  I agree that he's unlikely to get one from the utility, though, if he gets three-phase service from them.  If he is going to get three-phase directy from the utility he should discuss it with their sales people.  They might be able to supply 120/208 wye directly.


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## Wireaddict (Aug 28, 2014)

> If he uses an RPC he will have a wild leg. I agree that he's unlikely to get one from the utility, though, if he gets three-phase service from them. If he is going to get three-phase directy from the utility he should discuss it with their sales people. They might be able to supply 120/208 wye directly.



My RPC output only has 3-240V leads so I doubt if the mfgr added a center tap in one winding to create a wild leg, assuming it's wired in a delta configuration.  You've got me wondering, though, so tomorrow I'll turn it on & measure the phases to ground & report back if there's anything more than stray AC noise present.  If you choose to install a panel after your RPC make sure it's a 3-phase panel [has 3 (hot) main lugs & no neutral] & use 3-pole breakers to supply your 3-phase machines.  To protect the RPC don't exceed 80% of its full-load output current rating.  If the output is only rated in KVA divide it by 415.7 to find the amperage rating.  If the combined current rating of all the 3-phase motors exceeds 80% of the RPC's output current you should install a 3-pole breaker or fused disconnect switch between the RPC & the 3-phase panel to protect it & also satisfy the code.


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## John Hasler (Aug 28, 2014)

Wireaddict said:


> My RPC output only has 3-240V leads so I doubt if the mfgr added a center tap in one winding to create a wild leg, assuming it's wired in a delta configuration.  You've got me wondering, though, so tomorrow I'll turn it on & measure the phases to ground & report back if there's anything more than stray AC noise present.  If you choose to install a panel after your RPC make sure it's a 3-phase panel [has 3 (hot) main lugs & no neutral] & use 3-pole breakers to supply your 3-phase machines.  To protect the RPC don't exceed 80% of its full-load output current rating.  If the output is only rated in KVA divide it by 415.7 to find the amperage rating.  If the combined current rating of all the 3-phase motors exceeds 80% of the RPC's output current you should install a 3-pole breaker or fused disconnect switch between the RPC & the 3-phase panel to protect it & also satisfy the code.



The 240 single phase supply comes from the power company's center-tap-grounded transformer.    The RPC provides no isolation: L1 and L2 of the single phase go straight through and become L1 and L2 of the three phase.  L3 is generated by the RPC.  Thus you end up with what looks like a center tap grounded delta.


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## JimDawson (Aug 28, 2014)

This is a typical 3 phase, 240V, w/center tap ground/neutral service connection from the power company.


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## AlanR (Aug 28, 2014)

JimDawson said:


> This is a typical 3 phase, 240V, w/center tap ground/neutral service connection from the power company



We don't have that here but this is a 30,000 square foot, industrial building with its own HV from the pole, (big) step down transformer out back. The building internally sees straight 240 delta hence the transformers inside to provide 120 for lighting and such.

From the transformers we get 208 three phase and 120V, so we have either 240 or 208 three phase, our choice, depending where we connect things.


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## JimDawson (Aug 28, 2014)

AlanR said:


> We don't have that here but this is a 30,000 square foot, industrial building with its own HV from the pole, (big) step down transformer out back. The building internally sees straight 240 delta hence the transformers inside to provide 120 for lighting and such.
> 
> From the transformers we get 208 three phase and 120V, so we have either 240 or 208 three phase, our choice, depending where we connect things.




That would be typical of a heavy industrial power system.  I should have noted that I was talking about a light industrial/commercial service < 200 amps.


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## Wireaddict (Aug 29, 2014)

> The 240 single phase supply comes from the power company's center-tap-grounded transformer. The RPC provides no isolation: L1 and L2 of the single phase go straight through and become L1 and L2 of the three phase. L3 is generated by the RPC. Thus you end up with what looks like a center tap grounded delta.



I stand corrected about that.  Up to now I thought that RPCs did provide isolation unlike the quick & dirty 3 phase idler motors running on single phase & started via phase shifting caps, evidently RPCs don't have isolated outputs either, including mine.  Sorry if I added to anyone's confusion.


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## Cheeseking (Aug 30, 2014)

Wdnich I am in a somewhat similar situation in that i have 4 machines to run and am trying to decide how to best distribute from the converter.  7.5 hp rpc fed by 60A breaker.  Right now I have 2 outlets daisy chained but this is sort of a "rig" for time being.   I would not feel comfortable adding any more without proper distribution.  As suggested the best thing will probably be a 3 phase breaker panel fed by the converter.   Sorry for the crude sketch but this is how I wired mine.  










Sent from my iPhone using Tapatalk


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## Wireaddict (Aug 31, 2014)

Nice use of UniStrut to mount your equipment.


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## Cheeseking (Sep 1, 2014)

Ya the stuff is addicting.    A little pricey but 1001 uses in the shop.     


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## Cheeseking (Sep 10, 2014)

Well Wdnich your question/post inspired me...!!!!  I did some searching last week and picked up a 3P main lug panel and a couple 20A breakers and outlets on ebay.  Right now I have 4 three phase machines to run but only two outlets (my mill outlet is hacked/daisy chained off the lathes outlet).  I hooked it up this way short term not liking it but it was the easy way out at the time.   It will be quite a bit of rewiring, rearranging the shop etc but what I intended all along.    So thanks for bringing the topic up and sorry for corrupting your thread!


Btw 12 "spaces" = room for (4) 3-pole breakers.   I almost bought a 60A panel with 4 spaces which would only allow room for one 3 pole breaker.


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## Cheeseking (Mar 3, 2015)

And finally got around to installing the load center and running pipe to each machine.    My guess is this rig is way overkill for a simple one man shop but oh well.    To the point of another current thread I needed to make use of my trusty 2ton engine hoist to move the lathe out of the way.   I measured my voltages phase to phase and phase to ground with only the rpc idling and also under load and looked good.   
Also being somewhat anal decided straighten out the criss crossed liquidtite on the RPC at the expense of criss crossing wire internally! 


So my little system goes from 60A 1P breaker from main panel to 60A fused disconnect.


That feeds the nema1 magnetic starter/overloads to run RPC


RPC


RPC 3p 240 output to 30A fused disconnect.


To the Main Lug only 3p panel.






Pics of voltage are rpc idling unloaded
L1-L2.  L1-L3.  L2-L3
 Waitin on the cover panel bought on ebay.
I ran dedicated ground conductor on each circuit to each outlet.   Did not run any neutral conductors to keep things simple/separate.   I rather have 110 outlets not imbalancing my phases etc.


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## fast freddie (Mar 3, 2015)

LJP said:


> I have 2 shops, one for metal working, one for wood working. I have been running both rotary and static converters for over 25 years without problems. I use rotary converters for multiple machines as you suggest (shaper with feeder and dust collection). The machines that I want to turn on and off all day long (table saw, band saws etc.) are on static converters. Sliding table saw is 9 HP and runs great off a static converter. Thickness planer is 7.5 HP, static as well. This way I don't need to listen to the rotary all day long.
> 100 amp line is what I have as well, into each building from the main 200 amp service in the house. Never been a problem.
> I do not have separate breakers after the converters, it would be nice, but I don't think you need it.
> I do have 3 phase twist lock outlets so that machines can be disconnected easily (code in Mass.)
> Good Luck, Larry


all your motors running on static converters are in themselves rotary converters, it must be noisy when they are running.


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## Firestopper (Mar 11, 2015)

Hi,
I'm new to this site but can share my set up. I run eight different three phase machines from a single RPC. The system is protected by a 40amp breaker. The RPC runs very quiet and I can run all the machines at once so long as I start each machine one at a time.


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## Reeltor (Mar 12, 2015)

Cheeseking said:


> And finally got around to installing the load center and running pipe to each machine.    My guess is this rig is way overkill for a simple one man shop but oh well.    To the point of another current thread I needed to make use of my trusty 2ton engine hoist to move the lathe out of the way.   I measured my voltages phase to phase and phase to ground with only the rpc idling and also under load and looked good.
> Also being somewhat anal decided straighten out the criss crossed liquidtite on the RPC at the expense of criss crossing wire internally!
> 
> 
> ...




Your system is very neat and professional looking; I'd be embarrassed to show mine


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## JimDawson (Mar 12, 2015)

Nice shop.  But wayyyyy too clean!


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