Three phase static inverter questions...OMGA RAS

[Rick Potter]

I am thinking of buying a 14" Omga RAS with a 5HP, 3phase motor. I have regular 240 single phase in my shop. I have a 30A outlet.

I am thinking of a static inverter for it, because of price, and I have no intention of buying more three phase equipment. Someone...I think Larry Edgerton, uses a static inverter, and I have a couple questions about them.

I understand you lose about a third of the HP using one......is this correct? No problem for me, mostly 1" stuff anyway.

I have a Felder saw with an inverter of some sort from the factory. I have to turn it on separately, it spools up for about 10 seconds, then I can turn the saw on. It this the way a static inverter works, with a separate switch, or do I just turn on the saw for a quick cut like my DeWalt?


Thank you,
Rick Potter

[Michael W. Clark]

I have a static converter for my 5HP table saw. They advertise that it is 100% full power, but I've heard what you have heard as well. I haven't had a bit of trouble ripping any material as fast as I can push it through, maybe I would have the same experience with a 3HP?

As I understand it, the static converters use capacitors to induce a voltage on the third leg of the 3-Phase power which gets your motor turning. You need to put a disconnect before the converter on the single phase side. I used a 30A knife switch. Then the load side of the swith is wired to the converter. After the converter, run wire to the appropriate location on your tool. My saw has a magnetic switch so my 3-phase power is connected there.

The only problems I have had with the converter is during frequent start/stops. Sometimes the capacitors do not charge right away. You can cycle the disconnect switch or tap on the box and you will hear them re-charge. It makes a click (series of them sometimes) and a buzzing sound that tapers off after a couple of seconds. When changing blades or working on the saw, I throw the disconnect and hit the start button on the saw to discharge the capacitors. They have just enough usually to make "click" sound when you hit the start button. I don't think it could start the motor, but I would rather be safe.

They are really no problem to install once you have the single phase service ran.

Mike

[John McClanahan]

It sounds like your Felder saw is using a rotary converter. Any chance you could just tap into it?

John

[Bruce Page]

Rick, I run both a 5hp engine lathe and a 2hp milling machine off of a single HD Phase-O-Matic static converter. I know you loose a percentage of hp but I have never noticed it in either of my machines and I ran conventional 3phase machinery for many years.

I’ve been using the same static converter since the early 90’s.

[John Cooper2]

It sounds like your Felder saw is using a rotary converter. Any chance you could just tap into it?

John

+1, Sounds like your problem is solved. I agree that the Felder is using a RPC and they can run more than one machine.

[Rick Potter]

Thanks everyone,

I really appreciate the information. I am picking up the saw tomorrow. If so, I will then get serious about the converter.

About using the Felder converter.....I have decided I can live without the Felder, and it will be sold when I get around to it.

There is an interesting story to the new RAS. I will write about after I get it.

Rick Potter

[Larry Edgerton]

Rick

I did run the OMGA on a static converter for years but it burnt [static converter]out and I am running it off of the same rpc as the rest of the shop now. I always worried that it would burn out the motor on the saw as it is an unusual motor, but the motor is fine.

Don't use the saw a lot but it is a great saw, far better than the 16" Delta that it replaced. Have fun with it.

Larry

[Rick Potter]

Thanks Larry,

I have forgotten, what model Omga do you have? What does it crosscut?

Rick Potter

[Rollie Meyers]

A static converter starts a 3Ø motor & then drops out then the motor single phases, a RPC or a VFD would be a much better choice, here is one link for a A/C drive.

http://dealerselectric.com/item.asp?PID=4575

[David Kumm]

Felder runs with an internal VFD, not an RPC. You can buy a VFD for about $200 that will give you full power and a brake for the blade. It is the preferred way to go. Dave

[John McClanahan]

Felder runs with an internal VFD, not an RPC. Dave

Why does he need to give it a 10 second startup time?

John

[Noah Levy]

I'd like to know more about Dave's reply regarding a vfd for this application for $200?

I just spoke to the guys at Teco-Westinghouse today about a vfd for my 240volt 5hp 3ph jointer and they said that I would need a 10hp to cover the conversion power loss at the motor. The cheapest I could find that vfd was $610. Luckily, I have a 3hp single phase motor lying around so that's what I'll try first.

[Rick Potter]

I too, was interested in that $200 VFD. I looked on the internet and they were much more than that.

I did find a Baldor 5 HP RPC used for $375, but I understand that might not work on my 5 HP motor??

Is is possible to rewind a 3 phase motor for single phase?

Rick Potter

[Michael W. Clark]

I too, was interested in that $200 VFD. I looked on the internet and they were much more than that.

I did find a Baldor 5 HP RPC used for $375, but I understand that might not work on my 5 HP motor??

Is is possible to rewind a 3 phase motor for single phase?

Rick Potter

I don't have a VFD, but I believe the VFD prices go up considerably when you get above 3HP. They are very reasonable at 3HP and below and are probably the best choice unless you already have some other means of getting 3ph power.

I checked into rewinding my 3ph motor to single phase and was told that it can't be done. You can rewind from from single phase to 3ph, but not the other way, at least thats what I was told several years back when I got my TS. I bought a static converter and it was around $200.

Mike

[David Kumm]

Sorry about the $200 vfd quote. I was remembering the saw was a 3 hp rather than 5. I've bought several used 10 hp three in three out for use on a 5 hp motor with single phase in but the price is generally more like $300-350 and new is 500-600 best case. I don't know why the Felder takes 10 seconds to spool up unless there are some diagnostic checks it goes through. The VFD is running several motors so there is some electronics needed to allow that as generally a vfd is wired directly to the motor. Dave