I don't Understand

[automizer]

Ok I am going to be putting in a Hass GR-408 in my shop it needs 200-250 VAC, 3-phase 14kVA. I do not have 3-phase and to put it in to the shop would mean running 3 acrs or power line and 2 new power polls. Now I see static phase converters, rotary phase converters and VFD. What are all these? I have some idea of what they are goven the names but I do not understand why some people say good say bad. What exactly are they and could I use one of them to suite my needs. For the sake of argument lets say money is no object in this matter.

Any Thoughts?

[2muchstuff]

A seperate diesel generator.

[Ken_Shea]

Happy New year everyone !!

Static converters are in my opinion of no use at all, in your case not even a consideration.

A diesel generator is an option if you own a oil company.

Real three phase is way too expensive at least here in the states.

Rotary converters work well but a VFD if one is available for your power needs will likely be less cost and perhaps better, they seem to be well respected in every thing I have read on them.

[Russ Shugg]

A static phase converter is just a box with capacitors in it that makes a artificial third phase to help start a three phase motor off single phase. They work ok for light loads, but the motor only produces about 2/3 of rated horsepower. There is also a limit to how many times the motor can be started in any given time or the capacitors will overheat. A rotary phase converter is a motor that is started from single phase, using capacitors and the motor windings to produce an even, close to normal three phase output. If sized and built properly, a rotary convertor is about as close to three phase output as you can get and will run even the most sensitive CNC equipment. A VFD is a device that electronically produces variable frequency outputs to control the speed of 3 phase electric motors. Some (not all) VFD's can be hooked up to single phase and still produce 3 phase to run and control a motor speed. I think that a CNC rated rotary phase converter is the way to go. I have 3 in my shop, a 3 horse rated one for a grinder, a 10 horse rated one for my lathes and a 30 horse rated one to run my CNC's. I could of course run everything from the big one, but why start and run a 30 horse motor to run a 3 horse surface grinder. You can find CNC rated rotary converters reasonable on EBAY. I think I saw a 25 horse rated one for $1100.00 including shipping. Don't be afraid to purchase one a motor size or two bigger then your current requirements in case your operation grows or you want to run 2 or 3 machines at the same time,

[2muchstuff]

Well he did say for the sake of the argument that money was no option.

[widgitmaster]

Originally Posted by 2muchstuff Well he did say for the sake of the argument that money was no option.

Wish I could say that! :frown:

Eric

[Al_The_Man]

Originally Posted by Russ Shugg Don't be afraid to purchase one a motor size or two bigger then your current requirements in case your operation grows or you want to run 2 or 3 machines at the same time,

If your 3ph load is all 3ph motor, the rotary converter can be up to 60% smaller than the total load, but not smaller than your largest motor, as every 3ph motor on the system aids and acts as an assist to the rotary converter.
Al.

[Geof]

He will not actually have any three phase motors directly on the system so there are no inductive loads to assist the rotary converter. There are some small single phase loads such as coolant pump, fans and processor power supplies but the main load is not inductive in nature because the incoming supply is rectified onto a DC buss which supplies power for the servoes and spindle drive. Because he does not have other motors assisting the phase converter I suspect he is will be better off using a motor that matches the peak current draw of the machine which is a bit more than 50 amps on 208V three phase; i.e. in the ballpark of 20 hp.

[Russ Shugg]

Al, you are right in the case of manual machines especially. However in my experience, if you are running a CNC from the phase converter, and you start or reverse another machine from the converter it can drop the voltage momentarilly just enough to cause your CNC to error out. It was happening to me with my 10 hp converter running a r2e4 Boss9 bridgeport. I was tapping parts in my manual machine and every time I reversed the spindle to back out the tap my CNC would drop out.
Doesnt happen with my 30 hp convertor though. The 10 hp was a home brew and worked well, but probably wasn't balanced just right. By the way, you can but a CD with plans for all types of phase converters and specs for proper capacitor sizes etc on EBAY for $10. or so.

[Al_The_Man]

I have previously posted the way I made mine, there is also an article that helped me on the Metalworking drop box http://www.metalworking.com/ the files are FRW-().jpg in the 1998 retired file dir.
Al.

[automizer]

wow, ok so now I need a week to understand what you just said. I see a lot of you talking about DIY machines but frankly where were talking about the voltage we are I wont go near it. I have little experience with things such as this and when theres a 100 thousand dollar machine on the line I don't want to chance it. So now I basically understand the concept of a rotary converter so that covers the first part of my post. Now I guess (thanks to geof) im looking for roughly a 20hp converter commercial grade, this all has to be excepted my a licenced electrician as the place im buying my CNC from wont have it any other way. So this canadian boy is looking local any help?

[wisp]

I would take a look at Phase-a-Matic phase converters the home page is www.phase-a-matic.com

Some think they are a "cadillac" of phase converters. I have called and talked to them on the phone, very helpfull guys. They can tell you exactly what you will need.

cheers.