Value of used rotary phase converter?

I currently have a Phase-A-Matic static phase converter on my new to me Bridgeport mill. A used North America rotary phase converter is being offered to me but both seller and myself haven't come up with a fair value. It is the 7hp model and is over 20 years old but has sat in storage most of the time. What is a fair value for it?

beeser said:

I currently have a Phase-A-Matic static phase converter on my new to me Bridgeport mill. A used North America rotary phase converter is being offered to me but both seller and myself haven't come up with a fair value. It is the 7hp model and is over 20 years old but has sat in storage most of the time. What is a fair value for it?

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I wouldn't pay over $200 or so. I see on them craigslist all the time. Besides that, you can get the panel from WNY and pick up a used motor for $100 and have a brand new unit. The motor is no big deal. The capacitors in the panel are what go bad and need replacing occasionally. Wny sells replacement caps as well.

beeser said:

I currently have a Phase-A-Matic static phase converter on my new to me Bridgeport mill. A used North America rotary phase converter is being offered to me but both seller and myself haven't come up with a fair value. It is the 7hp model and is over 20 years old but has sat in storage most of the time. What is a fair value for it?

Click to expand...

I wouldn't pay over $200 or so. I see on them craigslist all the time. Besides that, you can get the panel from WNY and pick up a used motor for $100 and have a brand new unit. The motor is no big deal. The capacitors in the panel are what go bad and need replacing occasionally. Wny sells replacement caps as well.

beeser said:

I currently have a Phase-A-Matic static phase converter on my new to me Bridgeport mill. A used North America rotary phase converter is being offered to me but both seller and myself haven't come up with a fair value. It is the 7hp model and is over 20 years old but has sat in storage most of the time. What is a fair value for it?

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I'm guessing the static converter runs the mill OK, no issues starting it at any speed?
7 HP is way over kill for your machine IMO as I run a 2 HP mill with power feeds on a 2 HP ARCO rotary phase. What might help you decide if you really want what he has is to figure out what your goal is for the future, maybe a 16" lathe or some other machines that have 5 HP or bigger motors on them. I also suggest looking at new prices on ebay with free shipping, I found out that I could have bought one for $50 more new than I paid for the used converter and the new ones might be better. Another thing is some people have good enough connections that 3 phase motors are nearly free so the cost of building one is in the $100-$200 range for their home built version.
I have a total of 3 rotary phase converters, one in the basement, one in the attached garage and one in the work shop out back and the biggest is only 3 HP. All my machines are in the 2 or 3 HP range and find I can run several of them at the same time; reason I say 7 HP is over kill.
It would seem you have a few things to consider, hope what I said helps.
Dan

Thanks everyone for the feedback. Good point about 7hp being overkill. I read somewhere that you can't oversize a rotary so since the 7hp was offered I figured it's worth considering. I do plan to get another lathe that most likely will require 3 phase and a similarly powered bandsaw. Only one machine will be run at a time though. If I can't get it for $200 or less I'll look into the lesser powered units.

And no problems with the static converter starting the unit at the speeds selected so far.

You might want to look into VFD's. You could probably buy one cheaper than a rotary and it has a lot of features that you may not realize you want or need. You can learn about them in this forum: Transformers, Phase Converters and VFD.

In the beginning they can be intimidating. About 16 years ago when mine arrived I opened it up and looked through the manual. It looked so complicated and high tech I was overwhelmed. I put it back in the box and slid it under the bed. It was about a month before I got enough nerve to look at it again.
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Danny VanVoorn said:

Another thing is some people have good enough connections that 3 phase motors are nearly free so the cost of building one is in the $100-$200 range for their home built version.

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I spent less than $50 on my recent 3 hp home-built unit, and most of that was for the SO wire and the L15-30 plug and socket; the rest was for nice large color-coded start and stop switches. The motor I got from the scrap bin - the front end bell was broken in half, but I fixed it*; the capacitors, contactors, and 24v transformer I scrounged from the scrap pile of a neighbor who does HVAC. Scrap wood and various supplies already on hand completed the unit, and it works well powering my 2 hp Bridgeport.

*The motor was interesting - it is a 3 hp, TEFC motor with a cast-iron body, and as noted above the front end was broken in half. I was able to temporarily repair it using a large hose clamp around an internal hub that houses the front bearing - yes, a hose clamp, don't laugh - which let me verify that the motor ran okay. Once I decided to use it as a rotary converter, I made a more permanent repair using TIG brazing. I'm sure the result would be less than optimal if the motor were going into service to drive something, but the bearings don't growl, don't overheat, and it has been running strong as an RPC for 6 months now.

I put together my own phase converter with the help from another machinist friend who made his own. Do a search using "homemade three phase converter". You will find a lot of information and if you are inclined you can make your own.

Another vote for skipping any "Phase Converter" and going with a VFD if the Bridgeport is a Step Pully model. This way with the VFD you will get a complete Variable Speed of the motor via the VFD. Very hand to have when dialing in speeds of drill or endmill chatter by ear. I have linked to the one I prefer on a couple post over the last week. Pm me if you cant find it and are interested in the model.

200-300 for the converter. 7hp may be overkill for a BP but once you have the converter, all types of larger hp machines seem to start popping up all over the place. I think it is a good investment. You never know when a screaming deal 5hp lathe will show up on Craigslist.

B-Mathews said:

Another vote for skipping any "Phase Converter" and going with a VFD if the Bridgeport is a Step Pully model. This way with the VFD you will get a complete Variable Speed of the motor via the VFD. Very hand to have when dialing in speeds of drill or endmill chatter by ear. I have linked to the one I prefer on a couple post over the last week. Pm me if you cant find it and are interested in the model.

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That was the point I raised in another forum section. What advantage is there with a VFD if the mill has a mechanical variable speed control?

beeser said:

That was the point I raised in another forum section. What advantage is there with a VFD if the mill has a mechanical variable speed control?

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A good question. The main thing I know of - based on what I have heard only, since I don't have one - is that a VFD allows for soft-start and for electronic braking. IIRC, the downside is some loss of torque at lower speeds as compared to a mechanical speed control.

A rotary phase converter can power more than one machine, but as I understand it a VFD can only be used on one machine at a time.

beeser said:

That was the point I raised in another forum section. What advantage is there with a VFD if the mill has a mechanical variable speed control?

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As far as I'm concerned none!