I'm thinking of buying a large band saw available locally, 3 phase 230V. Is there any reasonable way I can convert this to use regular 230 or 120 volt circuits?

I'm not an electician, to say the least.

Any help or advice would be appreciated. Thanks.

...

Bet the VFD price will surprise you. Might be cheaper to replace the motor.

YEARS ago I could have picked up a commercial table saw in 3 phase for next to nothing. After running all the cost to get it to work on single phase I passed.

...

quote:

But you can find new 2hp or less VFDs on Ebay for $125 delivered.I bought 2 Allen Bradley 2 hp VFDs off Ebay for $75 each a few years ago.

That is a heck of a deal. Seems to me I was quoted over $300 and that was 10-15 years ago. (granger I think)


The guy next door has a set up in his garage. A couple capacitors and an idler motor. As I understand it the idler adds the 3 phase.

Since when I converted my band saw from 230 to 115 it ran backwards I'll let someone else convert their shop. I do agree 3 phase makes lot more sense if you are running much and needing power.

Just did a quick look on ebay. At those prices for a VFD I wish I had taken the saw. Hmmm wonder if they had ebay then.

Thanks for the help guys.

I'm not sure but I think the hp is about 2. It is an old Delta Model 20.

All things considered, especially my natural lethargy, I think I'm going to pass. It is already over $300 plus 18 1/4 per cent (tax and auction fees) and I have to go pick it up.

I certainly appreciate the advice though.

if you have 3 phase available you use it, but in general anything 5 hp or less will run fine on single. converters are a pain in the azz. you should be able to change the motor fairly cheap especially if you find a used motor. check the speed on the old one and make sure you get the same speed ( normal is 1725 rpm but there are lots of 3450 rpm out there) you might also need to change the starter, but 2 hp should be able to run off a HD switch. only way i'd go to a convertor is if i was to add other 3 phase equipment latter

by the way to change directions on the motor on 3 phase you switch the middle leg and one of the outsides, on single phase you reverse 2 wires in the motor connection box

Charlie, I have VFDs and rotary phase converters in my shop. I have several 3 phase machines in my shop. You can go to this website on their static converter and go to step 2 I believe. It will show you how to wire up a cheap rotary.

http://www.phase-a-matic.com/StaticDescription.htm

Drives warehouse has good prices. Id opt for a vfd for most applications. Quieter, soft start, speed control options.
Don

quote:

As I understand it the idler adds the 3 phase.

As I understand it, the idler motor balances the current created by the capacitors.

I have VFDs on my mill and lathe. For my big wood planer (20") and wide-belt sander I run them off a 10hp rotary converter.

...

Doug is correct. I have been in shops that started them with a pull rope and I've seen them use a little 110V motor to start them.

I run my 13 X 40 lathe and mill off of a rotary converter, you can't tell the difference.

quote:

Originally posted by butchloc:
by the way to change directions on the motor on 3 phase you switch the middle leg and one of the outsides, on single phase you reverse 2 wires in the motor connection box

To change direction on a 3 phase motor just switch any of the 3 phase wires, does not matter which are swapped around.

Single phase is more complicated, some can't be changed in direction, while those that can need the start capacitor wires changing around.

I use both a homemade rotoary phase converter and static converter, rotary phase converter will not de-rate you horse power, static converter are about 2/3 efficient, just bought a 3 phase table saw and works fine with 2hp motor also my clausing lathe with 2hp - 2 speed motor . don't be afraid of the 3-phase you can make it run pretty cheap.

quote:

Originally posted by butchloc:
by the way to change directions on the motor on 3 phase you switch the middle leg and one of the outsides, on single phase you reverse 2 wires in the motor connection box

That post brings up warm memories. My dad was a WW-II vet who was an officer trained in electronics. He was a pretty good shade tree electrician.

When I was about 14 he and I went to start up an irrigation pump on our farm for the first time in a season. The pump impeller was apparently frozen by accumulated rust or trash, so the 3-phase motor just hummed. It was twenty feet down in a hard-to-access hole, so things were not looking good for getting it started.

We puzzled over several different possibilities, short of the difficult chore of pulling the pump. Finally, I asked, "Dad, is there a way to make the pump run backwards so that it might clear the choke?" His eyes lit up. He quickly rewired the control box, flipped the switch, and, whirrrr went the pump motor. Five minutes later after swapping the leads back a gush of clear, cool well water was flowing.

quote:

Originally posted by eagle27:

quote:

Originally posted by butchloc:
by the way to change directions on the motor on 3 phase you switch the middle leg and one of the outsides, on single phase you reverse 2 wires in the motor connection box

To change direction on a 3 phase motor just switch any of the 3 phase wires, does not matter which are swapped around.

Single phase is more complicated, some can't be changed in direction, while those that can need the start capacitor wires changing around.

Just for the sake of conversation, with three phase, each phase is usually labeled as L1, L2, &L3 or A, B, & C and it is most common to swap A and C to reverse the motor. Or at least, that's what I've been taught to do.

quote:

Originally posted by Tex21:

quote:

Originally posted by eagle27:

quote:

Originally posted by butchloc:
by the way to change directions on the motor on 3 phase you switch the middle leg and one of the outsides, on single phase you reverse 2 wires in the motor connection box

To change direction on a 3 phase motor just switch any of the 3 phase wires, does not matter which are swapped around.

Single phase is more complicated, some can't be changed in direction, while those that can need the start capacitor wires changing around.

Just for the sake of conversation, with three phase, each phase is usually labeled as L1, L2, &L3 or A, B, & C and it is most common to swap A and C to reverse the motor. Or at least, that's what I've been taught to do.

Electrically it makes absolutely no difference at all which tails you swap to reverse a 3 phase motor but some are taught to swap side by side tails in the motor termination box as they will likely be of similar length and it will look neater rather than crossing over L1 to L3 etc. When I have ever terminated a motor or plug cable I make the tails all the same length.
I'm not an electrician but have wired up a lot of motors, and other equipment and fittings under the supervision of an industrial electrician and that was how he showed me.

That's because with a center tap delta service the hi leg is supposed to always be in the middle.
Don

Gato,
The price tier on this is the amp requirements of the 3ph motor -- if it is a 3hp or less, the VFDdrive is fairly cheap.. but you have to build a control... its a mild hassle .. all the parts can be had at radio shack for the control

Most vfds you can just program. Unless you are trying to vary the speed often no control is necessary.

You are very correct, but it sure is easy to vary the speed with a little twist of the pot.

Yes it is. I was just trying to state they can be installed just as easy or easier than a rotophase. So extra work and parts on the install shouldn't way the decision one way or the other.
Don

FWIW, I've been using a 3HP converter by American Rotary in my shop for 8 years now and have never had a problem with it. I installed the idler motor in my compressor shed which is outside the shop so when the three-phase is on you can't hear that motor running. I run my lathe, my mill and my surface grinder on it, but never all three at once. It will easily carry the mill and lathes simultaneously.

quote:

Originally posted by butchlambert:
You are very correct, but it sure is easy to vary the speed with a little twist of the pot.

There are VFDs on the market with a frequency dial in the unit, for those who do not have the skills or the time to build a simple control unit.

In Germany, we have three-phase power in virtually every household; I still use VFDs on all three-phase equipment because I like the soft start characteristics and the variable speed. With the current prices and availability of used VFDs, I would not even consider using a rotary converter for anything.

One of mine came with the potentiometer and I added it to another. I added braking resistors to one of them. Instant spindle stop is great.