Hertz convertor wanted

[Truxx1956]

Hey guys, I've got an old (1944 metal lathe) that I bought some time ago. Anyway, I've built a rotary phase convertor to run it, but at some time in it's history, someone has removed the hertz convertor which allows it to have high and low speeds. As of now, it only has high. With 3 phase you cant have a rheostat switch like on single phase so it cuts the hertz down to get a low speed. It's not a big deal, but I thought you guys may have one laying around?

Thanks in advance

 

[Elroy]

Get a VFD. They're getting down right cheap compared to what they once were.

 

[wrenchr]

I have given a few hertz donuts in my time!!!!!!!!!!

 

[alex71]

get yourself one of these. very inexpensive, and fantastic. I have one on my 3-phase mill and love it.

http://www.factorymation.com/s.nl/sc.2/category.13/.f

 

[Truxx1956]

I've seen them before, but heard bad things about them. I've heard they are hard on the 3phase motors? I dont know first hand, but am seriously considering changing over to a single phase motor if I could find one cheap enough. (I'm a cheapskate) I also have a 3phase Cincinnati Toolmaster mill that I would change too, but the power feed is a 1/4 hp 3phase too. To change the drive motor is no big deal, but the power feed is gear driven and would be harder. Not impossible, but harder.

Thanks for the input guys, I just thought someone may have one "cheap" or maybe a single phase 3hp motor cheap? Its got an 1 1/8" shaft on it. If I changed it over, I could clean up alot of extra wiring and junk.

 

[TheToolMan]

If your looking for some cheap used equipment look at our website www.plccenter.com go to the advanced search at the top

 

[-B-]

If in doubt of the virtues of the VFD just head on over to Practical Machinist and read.

 

[Major Ramifications]

If you doubt variable frequency drives, then go into any distribution plant, processing plant, bottling plant, brewery, etc, etc. that uses conveyors with these frequency drives on them. They are used heavily in
most types of conveyor systems.

 

[Truxx1956]

I may show my ignorance here, but if I go with a VFD, does that eliminate my phase convertor? Are they one in the same? Or what is the purpose of the VFD? I made my convertor with help from a maintinance man from a factory. It works well and we've metered the leads and everything checked out fine, but I still wouldn't mind doing away with it so I could not have as many wires running to the lathe and such. Its kind of nasty looking around the back of the lathe with all the "extra" junk on it.


Thanks guys

 

[Tornado]

There are VFDs available that can take a 1 phase input and run a 3 phase motor. This could eliminate the phase convertor and allow easy setting of the output frequency. The problems people have heard about VFDs being "hard" on motors is due in many cases to excessive motor lead lengths causing "reflected wave phenonomenon" and this condition can cause voltage spikes that burn up the first few turns of the motor windings. This problem occurs most often on 480v motors that are not inverter duty, not so much on 230v motors. Bottom line, keep the leads from the VFD to the motor to a few feet.