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Old 04-09-2008, 10:57 AM   #1
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3-phase


I have a 3-phase printing cutter that im trying to power up. I have a 200A service single phase of course...would I be able to power the cutter with a double-pole 30a and a single-pole 30A

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Old 04-09-2008, 11:06 AM   #2
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No. You cannot get three phase power from a single phase service without a 3 phase converter. Take a look here:

http://www.driveswarehouse.com/Drive...FQY_agodpX3RGQ

An alternative would be to swap the motor for a single phase motor.

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Old 04-09-2008, 11:09 AM   #3
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No. You do not have three phase service. There are a couple options to accomplish this task.
The best and cheapest option is a VFD. (variable freqeuncy drive). You put single phase in and get three phase out. It has varaible speed, but you can set it for a particular speed also. I need to know the hp, current and voltage to give you a ballpark price.
Another option is the phase converter. Very expensive to purchase and to operate. Shoot me an email and I can hook you up with a low cost VFD.

www.automationdirect.com
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Old 04-09-2008, 02:11 PM   #4
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Originally Posted by J. V. View Post
Another option is the phase converter. Very expensive to purchase and to operate. Shoot me an email and I can hook you up with a low cost VFD.

www.automationdirect.com
Sounds like you are indeed selling VFDs!

My 8 hp rotary phase converter (sized to power a total of 8hp worth of 3-phase machinery) is over 95% efficient. It is a high-end US made model, and cost about $1000. So purchase price could be expensive, depending on size and what you consider expensive (I'm powering equipment worth $10,000, so I don't consider that expensive, really). Solid state phase converters are appropriate for some small to moderate 3-phase loads, and they can be had for a couple hundred bucks (check the Grizzly Catalog). But there's no truth in the statement that phase converters are expensive to run. They use almost no electricity. Rotaries just induce the 3rd leg from the motion of the converter (which is basically a 3 phase motor with electronics to balance the 3 phases evenly). The rotor and windings in the motor simply induce the 3rd phase. Very little loss.

Solid state converters are less powerful, but if I recall correctly they're even more efficient. The downside is that it is equivalent to running your 3phase motor on 220 - the motor is only getting 2 pushes for each revolution instead of 3.
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Old 04-09-2008, 05:45 PM   #5
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A static phase converter will provide a 3 phase motor with very little starting torque. Sometimes even less than running torque. Also, you can safely load the motor to about 2/3 of its rated HP. These are commonly used with centrifugal pumps where the motor is grossly oversized, and starts no-load. They're the least expensive of all types of phase conversion. They are HP specific, you can't go outside of the range stamped on it. It's really nothing more than a box with some capacitors in it to 'generate' the third phase.

The rotary phase converter looks alot like a motor without a shaft, or has the shaft cut off. It's sort of like a motor and generator all in the same frame. These allow about 70-80% starting torque, and 80-90% of rated HP. They're rated in maximun HP, can drive smaller or multiple motors in any combination up to their rating. For example, a 50HP rotary phase converter can drive a 2HP motor just fine, a static one or a VFD can't. They're a bit more expensive, but they're much more versatile. These must be started first, then the 3 phase motor can be started.

A VFD will drive a 3 phase motor very well, many smaller ones will accept single phase input power. One disadvantage is that the 3 phase motor must be directly connected to the output, and the VFD becomes the controller. If a running motor is disconnected from a VFD, it'll go into a fault and must be reset to operate again. Some VFDs can be programmed to auto-reset. These are pretty spendy too.

A rotary phase converter can be easily wired to almost any machine with little or no modification. A VFD usually requires some modification to the maching its driving, usually not too difficult. Either one will operate most machinery at or near capacity.

Rob
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Old 04-09-2008, 06:26 PM   #6
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A static phase converter will provide a 3 phase motor with very little starting torque. Sometimes even less than running torque. Also, you can safely load the motor to about 2/3 of its rated HP. These are commonly used with centrifugal pumps where the motor is grossly oversized, and starts no-load. They're the least expensive of all types of phase conversion. They are HP specific, you can't go outside of the range stamped on it. It's really nothing more than a box with some capacitors in it to 'generate' the third phase.

The rotary phase converter looks alot like a motor without a shaft, or has the shaft cut off. It's sort of like a motor and generator all in the same frame. These allow about 70-80% starting torque, and 80-90% of rated HP. They're rated in maximun HP, can drive smaller or multiple motors in any combination up to their rating. For example, a 50HP rotary phase converter can drive a 2HP motor just fine, a static one or a VFD can't. They're a bit more expensive, but they're much more versatile. These must be started first, then the 3 phase motor can be started.

A VFD will drive a 3 phase motor very well, many smaller ones will accept single phase input power. One disadvantage is that the 3 phase motor must be directly connected to the output, and the VFD becomes the controller. If a running motor is disconnected from a VFD, it'll go into a fault and must be reset to operate again. Some VFDs can be programmed to auto-reset. These are pretty spendy too.

A rotary phase converter can be easily wired to almost any machine with little or no modification. A VFD usually requires some modification to the maching its driving, usually not too difficult. Either one will operate most machinery at or near capacity.

Rob
Damn Rob! Where did you learn all that? Seriously, what field are you in?
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Old 04-09-2008, 06:45 PM   #7
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I've been an electrician for about 18 years now, mostly comm'l/industrial. Some houses, usually big ones. The last job I was on was a power plant, I ran the control end of it. Lousy drawings (as usual), I did alot of the design and drawing correction myself. Absolutely love that type of work!

I've spent alot of time with motors, generators, and controls. I really like the technical end of electrical work. I know this sounds sort of strange, but the more complex the job is and the more problems there are, the more I enjoy it. I guess we all have our specialties.

Rob
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Old 04-10-2008, 12:35 AM   #8
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I will inject little more about the VSD's if you are running on single phase supply however you have to oversized due the hp / current rating between single and triphase supply like example

5 hp 3 motour you need the VSD at least 7.5 HP or larger size otherwise it will overheat pretty easy.

i just have one not too long ago with one of my customer he have 7.5 hp lathe machine and i used the VSD at 15 HP rating so i keep the unit cool so it dont overheat on performace wise.

Merci,Marc
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Old 04-12-2008, 11:19 AM   #9
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[quote=NateHanson;115004]Sounds like you are indeed selling VFDs!

Nate,
No, I am not selling VFD's. The reason I advised using one is my experience with them. I worked in the electric motor and drive repair business for several years. So I am familiar with VFD's and rotary phase converters. The reason I recommended the VFD is two fold. 1) it is generaly cheaper to purchase and repair, 2) Purchases and repairs on rotary converters are very expensive. If you ever need to have yours repaired you will see what I mean.

I just priced a 10hp VFD at 230 volt, 28 amp is $732.00

The VFD is the simplest way to go, and usually less money.

As far as derating VFD's for single phase, the poster was correct except you do not have to start derating until you get to 5hp or above. Most of the manufacturers allow this.

Everyone has their opinion, and all I was doing was presenting mine....John

PS...always size the VFD by current and not by HP

Last edited by J. V.; 04-12-2008 at 11:21 AM.
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Old 04-12-2008, 03:01 PM   #10
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Quote:
Originally Posted by micromind View Post
I've been an electrician for about 18 years now, mostly comm'l/industrial. Some houses, usually big ones. The last job I was on was a power plant, I ran the control end of it. Lousy drawings (as usual), I did alot of the design and drawing correction myself. Absolutely love that type of work!

I've spent alot of time with motors, generators, and controls. I really like the technical end of electrical work. I know this sounds sort of strange, but the more complex the job is and the more problems there are, the more I enjoy it. I guess we all have our specialties.

Rob
Your history sounds similar to my history. I even have the same name.

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Old 04-12-2008, 10:39 PM   #11
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Small world, isn't it? I've also spent a considerable amouint of time with medium-voltage switchgear with draw-out vacuum type breakers, 4160 to 34,500 volts. Controls and relays can get really interesting here. Alot of this is on power plants, so there's synchronization, generator protection, transformer protection, ect. to deal with. Really interesting.

Rob
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Old 04-13-2008, 11:00 AM   #12
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Originally Posted by micromind View Post
Small world, isn't it? I've also spent a considerable amouint of time with medium-voltage switchgear with draw-out vacuum type breakers, 4160 to 34,500 volts. Controls and relays can get really interesting here. Alot of this is on power plants, so there's synchronization, generator protection, transformer protection, ect. to deal with. Really interesting.

Rob
Interesting? not after 35 years! LOLOL I've been working at 5 generating stations (2300MW total capacity) as a electrical technician and quite frankly, I'm ready to retire and play golf! I mostly did windings, switchgear and auxiliary equipment. For the most part I love my trade and think it's the best field to be in!

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