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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => AC Power and Grounding => Topic started by: Mike Sokol on October 23, 2017, 08:51:05 am

Title: Rotary Phase Converter
Post by: Mike Sokol on October 23, 2017, 08:51:05 am
I'm in the middle of doing a bunch of demo gigs where we need to provide 3-phase 208 for up to four 1/2 motor for temporary lighting truss. The problem is, many of these churches don't have 3-phase power so I'm renting in a generator for a week at a time, just to turn it on long enough for the crew to run the truss motors. It's a pain and a waste of money when we just need 3-phase power for a few hours at load-in, and a few hours at load-out a week later. Has anyone used something like an American Rotary phase converter like this one to power maybe four 1/2 ton motors? I can buy one for the cost of a single week-long generator rental.

https://www.americanrotary.com/products/view/ar-pro-series

Title: Re: Rotary Phase Converter
Post by: Jeff Baumgartner on October 23, 2017, 08:53:45 am
Why not just rent/buy single phase motors?
Title: Re: Rotary Phase Converter
Post by: Steve M Smith on October 23, 2017, 09:00:29 am
Can you do it like this?

https://www.electricneutron.com/electric-motor/use-three-phase-motor-single-phase-power-supply/


Steve.
Title: Re: Rotary Phase Converter
Post by: Mike Sokol on October 23, 2017, 09:21:21 am
Can you do it like this?

https://www.electricneutron.com/electric-motor/use-three-phase-motor-single-phase-power-supply/


Steve.

No, this has to run through a standard 4-pack motor controller, so I'm pretty sure it won't work.

Title: Re: Rotary Phase Converter
Post by: Mike Sokol on October 23, 2017, 09:25:05 am
Why not just rent/buy single phase motors?

Buying four single-phase lift motors costs WAY more than a phase converter, plus I'll need a central controller box to run them. In addition we would have to do yearly inspections, etc. I would much rather have the A-V crew who are already supplying the truss and lights just bring their own 3-phase motors and controller, and I'll drop them 3-phase 208 on cams.
Title: Re: Rotary Phase Converter
Post by: Mac Kerr on October 23, 2017, 10:07:31 am
I'm in the middle of doing a bunch of demo gigs where we need to provide 3-phase 208 for up to four 1/2 motor for temporary lighting truss. The problem is, many of these churches don't have 3-phase power so I'm renting in a generator for a week at a time, just to turn it on long enough for the crew to run the truss motors. It's a pain and a waste of money when we just need 3-phase power for a few hours at load-in, and a few hours at load-out a week later. Has anyone used something like an American Rotary phase converter like this one to power maybe four 1/2 ton motors? I can buy one for the cost of a single week-long generator rental.

https://www.americanrotary.com/products/view/ar-pro-series

Those phase converters are intended for running 3Ř motors so I would expect it to work. They are used all the time in home shops that have 3Ř machinery. It is intended for permanent installation, so may need some packaging.

I still can't get my head around how they work, but they do seem to work.

Mac
Title: Re: Rotary Phase Converter
Post by: Mike Sokol on October 23, 2017, 10:21:36 am
Those phase converters are intended for running 3Ř motors so I would expect it to work. They are used all the time in home shops that have 3Ř machinery. It is intended for permanent installation, so may need some packaging.

I still can't get my head around how they work, but they do seem to work.

Mac

I just talked to their application engineer and he says they're 3P Delta output with 240V between the legs, not 208V. I might need to get a buck-boost transformer on the input to drop the voltage a bit since I'm not sure the lift motors are rated for 3P/240V. Still, it's a possibility. 
Title: Re: Rotary Phase Converter
Post by: Mike Sokol on October 23, 2017, 10:45:45 am
I just talked to their application engineer and he says they're 3P Delta output with 240V between the legs, not 208V. I might need to get a buck-boost transformer on the input to drop the voltage a bit since I'm not sure the lift motors are rated for 3P/240V. Still, it's a possibility.

I just looked, and it appears that most 3P chain hoist motors are rated at 230 volts, so I won't need a buck-boost transformer to drop the voltage. I'm guessing 230/240 volts would work just fine.
Title: Re: Rotary Phase Converter
Post by: Mike Sokol on October 23, 2017, 11:08:36 am
I just talked to the marketing/applications department at Phase-A-Matic and they're telling me I need a 20 horsepower rotary converter to run four 1-ton lifts. And it needs a 125-amp/120-volt breaker on the input of the converter. They're just looking at their marketing literature and won't let me talk to an engineer about the application. I need to measure actual current draw when I'm there next week.
Title: Re: Rotary Phase Converter
Post by: Frank Koenig on October 23, 2017, 11:12:35 am
If you want a project I think you can make your own funky phase convertor from a three-phase motor running on a single phase using one of its windings and a small single-phase motor with a belt clutch that you use to start the three-phase motor. The other two phases are taken from the non-driven windings of the the three-phase motor. I'm sure you can find plans with motor sizing guidance on the Internet. While not for industrial use, such a rig might have educational value in and of itself. -F
Title: Re: Rotary Phase Converter
Post by: Art Welter on October 23, 2017, 11:38:01 am
I just talked to the marketing/applications department at Phase-A-Matic and they're telling me I need a 20 horsepower rotary converter to run four 1-ton lifts. And it needs a 125-amp/120-volt breaker on the input of the converter. They're just looking at their marketing literature and won't let me talk to an engineer about the application. I need to measure actual current draw when I'm there next week.
Mike,

Sounds like they are going conservatively overboard for 4 two HP motors- 20HP for 8HP?
Also consider that chain motors lift quite slowly, you could run only one pair at a time, alternating stage left and right and use 1/2 the capacity rotary converter.

Art
Title: Re: Rotary Phase Converter
Post by: TJ (Tom) Cornish on October 23, 2017, 11:55:54 am
If you want a project I think you can make your own funky phase convertor from a three-phase motor running on a single phase using one of its windings and a small single-phase motor with a belt clutch that you use to start the three-phase motor. The other two phases are taken from the non-driven windings of the the three-phase motor. I'm sure you can find plans with motor sizing guidance on the Internet. While not for industrial use, such a rig might have educational value in and of itself. -F
It's my understanding that this is how all rotary phase converters work - homemade or commercial, though I have never seen the need for a starter motor. 

Making your own is easy, though may require a little trial and error with capacitor values to level the voltages of each phase.
Title: Re: Rotary Phase Converter
Post by: Frank Koenig on October 23, 2017, 12:17:03 pm
It's my understanding that this is how all rotary phase converters work - homemade or commercial, though I have never seen the need for a starter motor.

I think that's right. But I'm guessing that the purpose-built phase convertors are optimized (and have a built-in starting winding, etc.). I recall that the home brew ones require a convertor motor with several times the power rating of the motor to be driven, so can be pretty heavy for what they do. -F
Title: Re: Rotary Phase Converter
Post by: Stephen Swaffer on October 23, 2017, 12:21:16 pm
Why not use a VFD? They take 3 phase to DC then back to 3 phase.  You can get them that will spec being usable on single phase supplies-usuallu have to oversize them a bit.  Also, you can run mutilple motors on a VFD.  Probably cheaper and lighter than a rotary.
Title: Re: Rotary Phase Converter
Post by: Tim McCulloch on October 23, 2017, 12:31:34 pm
Back when I was in highschool and working as a projectionist at the local Rialto Theater we had rotary phase converters for the arc lamp supplies.  Everything else in the booth ran on single phase...

I don't recall that I ever noticed who made them but I know they ran flawlessly for a couple of decades and might still be in use to run the new xenon lamps that were installed 20 years ago.

As for motor load, Columbus-McKinnon publishes full load specifications for all their hoists.  A 1-ton, 16 FPM 3 phase 208v hoist draws <4 Amperes per leg.  Contact Dave Carmack at C-M if you have questions.
Title: Re: Rotary Phase Converter
Post by: TJ (Tom) Cornish on October 23, 2017, 01:02:46 pm
Why not use a VFD? They take 3 phase to DC then back to 3 phase.  You can get them that will spec being usable on single phase supplies-usuallu have to oversize them a bit.  Also, you can run mutilple motors on a VFD.  Probably cheaper and lighter than a rotary.
VFDs blow up if you disconnect the load while running - the back EMF toasts the IGBT devices.

Mike's application is powering an existing motor controller and setup which would use conventional switches/solenoids to turn the winch motors on and off.
Title: Re: Rotary Phase Converter
Post by: Mike Sokol on October 23, 2017, 01:37:46 pm
VFDs blow up if you disconnect the load while running - the back EMF toasts the IGBT devices.

Mike's application is powering an existing motor controller and setup which would use conventional switches/solenoids to turn the winch motors on and off.

Exactly right. I want to provide 3-phase cam outputs with maybe 20 amps per leg at 230ish volts. I've talked to several rotary converter manufacturers today, and they all seem a bit lost with my questions.
Title: Re: Rotary Phase Converter
Post by: Tom Bourke on October 23, 2017, 01:49:20 pm
One of my hobbies is CNC and machine tools.  The forums I am on for that talks about single to 3 phase conversion all the time.

American Rotary sponsors one of the vintage machine youtube channels.  They also seam to have a good product and service.  I would tend to buy from them if I was not making my own.

I know of several ways to get 3 phase from single phase.

Of them I think a rotary is probably the best.  However I would defer to your chain motor and American Rotary having a conversation.  They have some regulated options.  I just don't know how sensitive a chain motor would be.  For CNC use I hear 2X the spindle current as a common multiplier for sizing a converter to load, regardless of who makes the converter. 

The second kind is a solid-state capacitor bank.  They work like a capacitor start / capacitor run motor only using your 3 phase motors as the motor.  they require tuning to load and are not as smooth as other methods.  The generated leg can get wild with varied loads. 

VFD generally require no switching between the motor and the drive.  They will blow up with a switched load.  Having said that, maybe there are units designed for this?  I have not seen one.  All they really are is an inverter.
Title: Re: Rotary Phase Converter
Post by: Tom Bourke on October 23, 2017, 01:57:26 pm
Exactly right. I want to provide 3-phase cam outputs with maybe 20 amps per leg at 230ish volts. I've talked to several rotary converter manufacturers today, and they all seem a bit lost with my questions.
My guess is that a chain motor is not a load they hear about very much, if ever.  Even with a rotary converter the generated leg will be a bit wild.  Controls and electronics need to stay on L1 and L2.  L3 is the generated leg.  You can't really treat them like a generic utility provided service.
Title: Re: Rotary Phase Converter
Post by: Mac Kerr on October 23, 2017, 03:10:41 pm
American Rotary sponsors one of the vintage machine youtube channels.  They also seam to have a good product and service.  I would tend to buy from them if I was not making my own.

Keith Rucker?

Mac
Title: Re: Rotary Phase Converter
Post by: Stephen Swaffer on October 23, 2017, 03:23:37 pm
 
VFD generally require no switching between the motor and the drive.  They will blow up with a switched load.  Having said that, maybe there are units designed for this?  I have not seen one.  All they really are is an inverter.


A VFD might not be a workable solution-but modern ones don't seem to be that touchy.  See this from A-B's Powerflex manual:

ATTENTION: To guard against drive damage when using output contactors, the
following information must be read and understood. One or more output
contactors can be installed between the drive and motor(s) for the purpose of
disconnecting or isolating certain motors/loads. If a contactor is opened while
the drive is operating, power is removed from the respective motor, but the drive
continues to produce voltage at the output terminals. In addition, reconnecting
a motor to an active drive (by closing the contactor) could produce excessive
current that can cause the drive to fault. If any of these conditions are
determined to be undesirable or unsafe, wire an auxiliary contact on the output
contactor to a drive digital input that is programmed as “Enable.” This causes the
drive to execute a coast-to-stop (cease output) whenever an output contactor is
opened.

So an occasional switch is not a huge deal-jogging a chain motor in to place probably would be.

I guess my impression is that phase converters are happier with a steady load as well.
Title: Re: Rotary Phase Converter
Post by: Tim McCulloch on October 23, 2017, 03:41:45 pm
A VFD might not be a workable solution-but modern ones don't seem to be that touchy.  See this from A-B's Powerflex manual:

ATTENTION: To guard against drive damage when using output contactors, the
following information must be read and understood. One or more output
contactors can be installed between the drive and motor(s) for the purpose of
disconnecting or isolating certain motors/loads. If a contactor is opened while
the drive is operating, power is removed from the respective motor, but the drive
continues to produce voltage at the output terminals. In addition, reconnecting
a motor to an active drive (by closing the contactor) could produce excessive
current that can cause the drive to fault. If any of these conditions are
determined to be undesirable or unsafe, wire an auxiliary contact on the output
contactor to a drive digital input that is programmed as “Enable.” This causes the
drive to execute a coast-to-stop (cease output) whenever an output contactor is
opened.

So an occasional switch is not a huge deal-jogging a chain motor in to place probably would be.

I guess my impression is that phase converters are happier with a steady load as well.

For chain hoists the starting current is the same a locked rotor current.  C-M also publishes those numbers.

If folks truly understood what "bumping" a hoist does to it (and they had to personally pay for the maintenance) they might not be so fast to jump around on the controller buttons.
Title: Re: Rotary Phase Converter
Post by: Tom Bourke on October 23, 2017, 08:11:11 pm
Keith Rucker?

Mac
Yep,  Keith.  I also follow This old Tony, mrpete222, Clickspring, Abom79, Keith Fenner and a few others I can't think of right now. 
Title: Re: Rotary Phase Converter
Post by: Mac Kerr on October 23, 2017, 08:18:38 pm
Yep,  Keith.  I also follow This old Tony, mrpete222, Clickspring, Abom79, Keith Fenner and a few others I can't think of right now.
Yeah, al of those and a few more. NYCNC, Oxtool, Dave Richards steam shop, some woodworkers.

I'm planning on visiting Keith Fenner this summer when I'm on the Cape. When I was there this year Keith was in Rancho Cucamonga with Stan Zinkowski.

Mac
Title: Re: Rotary Phase Converter
Post by: Tom Bourke on October 23, 2017, 08:20:54 pm
Yeah, al of those and a few more. NYCNC, Oxtool, Dave Richards steam shop, some woodworkers.

I'm planning on visiting Keith Fenner this summer when I'm on the Cape. When I was there this year Keith was in Rancho Cucamonga with Stan Zinkowski.

Mac
Yup, all names I recognize!
Title: Re: Rotary Phase Converter
Post by: Jonathan Johnson on October 26, 2017, 02:57:19 pm
OK, here's a wild idea. Not even close to half-baked yet. It's worth at least as much as you paid for it.

Take three inverter generators. Bond their neutrals together, but instead of bonding the hots with the paralleling jack, use some kind of three-phase drive circuit to sync each generator 120° apart in a wye configuration.

DISCLAIMER: I am not an electrical engineer.

P.S. -- If you patent this, Mike, send me a dollar.
Title: Re: Rotary Phase Converter
Post by: TJ (Tom) Cornish on October 26, 2017, 03:30:46 pm
OK, here's a wild idea. Not even close to half-baked yet. It's worth at least as much as you paid for it.

Take three inverter generators. Bond their neutrals together, but instead of bonding the hots with the paralleling jack, use some kind of three-phase drive circuit to sync each generator 120° apart in a wye configuration.

DISCLAIMER: I am not an electrical engineer.

P.S. -- If you patent this, Mike, send me a dollar.
Step 1: Get 3 generators.
Step 2: Hook them together with some thingy that makes the power 3-phase-ish.
...
Step 4: Profit!

 ;D
Title: Re: Rotary Phase Converter
Post by: Mike Sokol on October 26, 2017, 03:44:04 pm
OK, here's a wild idea. Not even close to half-baked yet. It's worth at least as much as you paid for it.

Take three inverter generators. Bond their neutrals together, but instead of bonding the hots with the paralleling jack, use some kind of three-phase drive circuit to sync each generator 120° apart in a wye configuration.

DISCLAIMER: I am not an electrical engineer.

P.S. -- If you patent this, Mike, send me a dollar.

Yeah, that's the first thing I thought of. My thought was since these inverter generators will sync to any parallel source, all you would have to do it build a tiny 3-phase signal generator. That might work with WYE loads, but probably not with Delta motor loads. 
Title: Re: Rotary Phase Converter
Post by: David Buckley on October 26, 2017, 05:57:11 pm
That might work with WYE loads, but probably not with Delta motor loads.

Since we're madcapping: have a small three phase wye motor-generator, and run the motor off house power.  Get the three Hondas and connect them wye to the rotary generator.  Add your delta loads.  The generators should be happy as all each of them sees is a single phase load.

The only fun bit is making sure the droop on the MG set works with the Honda's so that the majority of the load is fed from the Hondas.
Title: Re: Rotary Phase Converter
Post by: Cailen Waddell on October 26, 2017, 06:09:24 pm
Has anyone discussed a big single phase motor and a 3 phase generator, connected with a belt?   I ask because I know a guy who ran a 3 phase c-n-c machine in his basement with one... seemed to work fine


Sent from my iPhone using Tapatalk
Title: Re: Rotary Phase Converter
Post by: Mike Sokol on October 26, 2017, 06:23:52 pm
Has anyone discussed a big single phase motor and a 3 phase generator, connected with a belt?   I ask because I know a guy who ran a 3 phase c-n-c machine in his basement with one... seemed to work fine


Sent from my iPhone using Tapatalk

Of course that works, but it's seen as too expensive and inefficient to be practical. But if I had a spare 3-phase generator laying around it would be pretty cool.
Title: Re: Rotary Phase Converter
Post by: Stephen Swaffer on October 27, 2017, 04:32:30 pm
Yeah, that's the first thing I thought of. My thought was since these inverter generators will sync to any parallel source, all you would have to do it build a tiny 3-phase signal generator. That might work with WYE loads, but probably not with Delta motor loads.

So, an inverter genny (I assume) takes DC bus and "Inverts" it into 120 VAC.  Putting 3 of these together and synchronizing them makes 3 phase output.

A freq drive takes an AC supply, converts it to a DC bus, and creates 3 synchronized phases 120 deg apart.

Sounds like we are re-inventing the wheel?

Title: Re: Rotary Phase Converter
Post by: Tim McCulloch on October 27, 2017, 07:33:43 pm
So, an inverter genny (I assume) takes DC bus and "Inverts" it into 120 VAC.  Putting 3 of these together and synchronizing them makes 3 phase output.

A freq drive takes an AC supply, converts it to a DC bus, and creates 3 synchronized phases 120 deg apart.

Sounds like we are re-inventing the wheel?

STOP THE MADNESS!!!  The phase wheel is now running backwards!

I hope you kids are happy with yourselves.

/snark
Title: Re: Rotary Phase Converter
Post by: Mike Sokol on October 27, 2017, 07:50:14 pm
STOP THE MADNESS!!!  The phase wheel is now running backwards!

I hope you kids are happy with yourselves.

/snark
😊
Title: Re: Rotary Phase Converter
Post by: Mark Cadwallader on October 27, 2017, 08:21:31 pm
😊

That's a real fancy-ass bumper car you have, Mike.
Title: Re: Rotary Phase Converter
Post by: Stephen Swaffer on October 27, 2017, 11:07:41 pm
I realize that the waveform's on VFD's are designed and optimized for running 3 phase motors (but that is what the OP was about running).  Guess I'm just trying to figure out what the magic device is that let's a Honda inverter genny run an AC unit-starting and stopping motors, etc.  Run power tools-starting and stopping motors, etc. etc.  without blowing up-but a VFD can't do the same?  Down inside the magic box it is physics at work-the electrons don't know if they're in an inverter genny, or a vfd.  It might be a good idea to have load reactor (maybe just a 3 phase iso transformer?) for protection? 
Title: Re: Rotary Phase Converter
Post by: Tom Bourke on October 28, 2017, 09:14:50 am
I realize that the waveform's on VFD's are designed and optimized for running 3 phase motors (but that is what the OP was about running).  Guess I'm just trying to figure out what the magic device is that let's a Honda inverter genny run an AC unit-starting and stopping motors, etc.  Run power tools-starting and stopping motors, etc. etc.  without blowing up-but a VFD can't do the same?  Down inside the magic box it is physics at work-the electrons don't know if they're in an inverter genny, or a vfd.  It might be a good idea to have load reactor (maybe just a 3 phase iso transformer?) for protection?
I think it has to do with design goals. If you assume the load is going to be a motor hard wired you design for that.  This let's you use the counter EMF and other characteristics to your advantage for stability or efficiency.   The tradeoffs may include a sensativity to disconnect.

The other tradeoff may be cost of parts vs robustness. The reality is that inverters, audio amps, and vfd all use the same technologies.  Some amps are more robust than others. Overall newer technology has improved costs and robustness.  This is true for all of these applications.
Title: Re: Rotary Phase Converter
Post by: Frank Koenig on October 28, 2017, 11:15:17 am
I think it has to do with design goals. If you assume the load is going to be a motor hard wired you design for that.  This let's you use the counter EMF and other characteristics to your advantage for stability or efficiency.   The tradeoffs may include a sensativity to disconnect.

The other tradeoff may be cost of parts vs robustness. The reality is that inverters, audio amps, and vfd all use the same technologies.  Some amps are more robust than others. Overall newer technology has improved costs and robustness.  This is true for all of these applications.

This. Power electronics is a complex, subtle, and, in my opinion, under appreciated business. I'm impressed as hell with the motor drives they're putting in cars that are about the size of a breadbox and can handle a good chunk of a MW at ~400 V while letting you finesse that fixed-gear induction motor to drive smoothly at < 1 mph. -F
Title: Re: Rotary Phase Converter
Post by: Stephen Swaffer on October 28, 2017, 03:42:06 pm
I agree-in my day job I deal with inverters from 1 hp to 300 Hp running on both 480 V and 230 V.  The technology has advanced tremendously over the last 10 years-dropping the price to where you can put a drive in instead of an across the line contactor for some loads at a very small increase in cost.  Ten years ago we started using inverter welders where Lincoln could actually design a waveform to minimize splatter-instead of just making a sine wave "work".  Obviously welding is a lot of make and break under load-and the load is actually a short circuit.

How long have Honda genny's been on the market?

I wonder how much of the wisdom that you can't disconnect under load is old thinking-thinking that in 99% of applications is probably best practice anyway?  Often, no good reason to challenge it.

Except for liability when dealing with a hoist (yes I know the ins and outs of overhead hoists), the ideal thing-and probably most cost effective for Mike would be to eliminate the contactors and drive the chain motors with a drive.  Of course, you'd have to wire in limits, etc-but think about the mechanical wear and tear savings as you decel slowly into place and accel slowly to take up mechanical slack. 

The quote I inserted up thread is current from a major manufacturer-and it really doesn't give a stern warning about damaging the drive.  It wouldn't cost a lot to upsize a drive to 300-400% capacity if you were going to "abuse" it.

Not trying to be argumentative-but I can be hard headed when asking "why" at times.  Sometimes it works out, sometimes not.

Actually it looks like someone is already doing this:

https://www.americanrotary.com/products/view/ad-digital-smart-series

A digital 1 phase-3 phase converter 1.5 HP start is smallest they do-$577.  Still pricey-but it would be very portable.

Title: Re: Rotary Phase Converter
Post by: Tim Padrick on October 29, 2017, 05:20:40 am
Mike, email me at work, tim at jonas productions dot com.  We have a RotoPhase that we might sell.
Title: Re: Rotary Phase Converter
Post by: Mike Sokol on October 31, 2017, 07:32:06 pm
Mike, email me at work, tim at jonas productions dot com.  We have a RotoPhase that we might sell.

done...