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Author Topic: Rotary Phase Converter  (Read 1315 times)

Stephen Swaffer

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Re: Rotary Phase Converter
« Reply #20 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.
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Steve Swaffer

Tim McCulloch

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Re: Rotary Phase Converter
« Reply #21 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.
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Tom Bourke

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Re: Rotary Phase Converter
« Reply #22 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. 
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Mac Kerr

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Re: Rotary Phase Converter
« Reply #23 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
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Tom Bourke

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Re: Rotary Phase Converter
« Reply #24 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!
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Jonathan Johnson

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Re: Rotary Phase Converter
« Reply #25 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.
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Stop confusing the issue with facts and logic!

TJ (Tom) Cornish

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Re: Rotary Phase Converter
« Reply #26 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
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Mike Sokol

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Re: Rotary Phase Converter
« Reply #27 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. 

David Buckley

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Re: Rotary Phase Converter
« Reply #28 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.
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Cailen Waddell

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Re: Rotary Phase Converter
« Reply #29 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


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