Emergency buying advice needed!!!!

[Mark Versprille]

I'm looking at a PM 66. good condition. It's a 3 phase machine. I have single phase power. Price $600. What do I do?

[Jim O'Dell]

Are you ready to spend some more money to be able to run it after the 600.00? You'll need a new motor, or some type of phase convertor (I'm not the one to ask about those!) to run it on single phase electrical. But if it's in good shape, it could be a steal!! Jim.

[Fred Hargis]

Be aware the machine will either have to 1.) have a new motor and maybe a switch, or 2.) install a phase converter or VFD (unless you have phase power). The guys over at OWWM swear the 3 phase motors are so superior it's worth the effort to install the VFD or converter. I've seen a lot of convertors on CL lately, but it would still run another $250 +, plus the installation if you have it done. If all of this reads like greek, then you may want to wait for the next one.

[Rod Sheridan]

If it's in good condition and 3 HP I'd buy it, and install a Variable Frequency Drive on it.

If it's 5 HP and for home use, I'd replace the 5 HP 3 phase motor with a 3 HP single phase.

Regards, Rod.

[Jerome Hanby]

If it was in good shape, I'd buy it quick. Of course, I think tinkering with the three phase would be fun...

[Mark Versprille]

I passed on the PM 66. The one I was looking at (there were two) found a home while I was vacillating. The other has a problem with the blade lift. It takes about 15# of pressure to turn the wheel. The guy selling them is a nice guy whose business is reselling used industrial tools. He also has a 12" Grizzly 7 1/2 hp in mint condition for $1,200. That's so much more than I need I didn't really consider it, not really, maybe just a little bit. They are on the NJ Craigslist, in the NY suburbs section.

[John Bailey]

Although you missed this one, don't let 3 phase bother you in the future. I had doubts but bought a 3 phase bandsaw and added a VFD and I love the combination.

John

[Scott T Smith]

I have quite a bit of 3 phase equipment, that operates both off of phase converters as well as generators. I also have installed several VFD's.

My advice is do not be afraid of 3-phase equipment! Many times you can pick up a better deal on used equipment, and using/installing a converter is no big deal.

As previously stated, consider a VFD for 3ph and under motors, unless you are planning to have multiple 3-phase machines. Over 3hp or for multiple machines I prefer a rotary phase converter.

With a rotary converter, you basically have three choices for installation. The first choice is the slave the converter to the piece of equipment. Fast, easy, but requires one converter per machine.

The second choice is to wire it so that you have a 240V single phase plug on the incoming line, and a 240V 3-phase 4 conductor twist-loc connector on an outgoing line. Attach some casters to the converter and it allows you to roll it from machine to machine as needed (or to put it in-between two different 3-phase machines and share common wiring. The only other thing that you'll need to do is to put twist-loc plugs on your 3-phase machines so that you can plug them into the converter as needed.

The third choice is to install a three phase load center, and power it off of the converter. Run dedicated wiring to your various pieces of 3-phase equipment from the load center.

Size the converter for your largest motor, plus a little extra. If you're considering any 7.5 hp equipment, then look around for a 10 hp converter.

Wiring the converter is very simple and straightforward.

The other nice thing about choices 2 and 3 is that once you've made the investment in the converter, you won't need another one for future 3-phase machines.

[Rob Diz]

So let's say I was looking at a Uni or PM 66 with a 3hp 3ph motor. How would the VFD work, and which one would you buy if you had a small shop?

I'm also curious what the downside is to having a VFD?

[Scott T Smith]

So let's say I was looking at a Uni or PM 66 with a 3hp 3ph motor. How would the VFD work, and which one would you buy if you had a small shop?

I'm also curious what the downside is to having a VFD?

North American electric motors are designed for 60 cycles (or hertz), which basically means that your current is alternating 60 times a second (or that you're getting 60 pulses a second of electricity to the motor). Motors are designed to operate at a specific RPM (usually either 3,400 or 1,750 based upon the 60 cycles of current.

A VFD lets you electronically vary the frequency from 60 cycles down to 0. If you operate an electric motor at 30 cycles per minute instead of 60, it is basically going to spin at half the RPM.

The downside regarding a VFD for some 3-phase applications is that you need to control you motor with the VFD, instead of the typical on-off switch, and most VFD's will not let you start the motor up at full speed - rather they require you to spool them up and down from zero. It can several seconds longer for a motor to go from stationary to working speed with the VFD.

Something like a table saw, where you might turn it on and off multiple times in a short amout of time and require it to operate at full motor speed would be a bit of a pain (IMO) with a VFD. A piece of equipment where you might not turn it on and off so much, or one that can benefit from varying the motor speed (such as a bandsaw, drill press or shaper), is a better VFD application.