3 Phase Variable Frequency Drives

I am somewhat familiar with these https://www.galco.com/acs150-03u-09a8-2-abbi.html but made my own radial phase converter out of a 7.5 HP 3 phase motor and a static phase converter for start up.

I put new bearings in the 7.5 hp 3 phase motor, but it still makes noise. It’s probably the sheer size of the thing with fan. It’s about 50 years old and used to be a dewalt 20” radial arm saw.

anyway, it’s old and I have no idea how “in phase” this motor creates power. Also, I made this whole electrical nightmare to power a lathe and my mill out of junk.

question is, would it be worth my while to buy one of these to power both machines or buy 2 for both of them or should I just keep in working with this old cobbled together bunch of garbage? I feel it’s safe, but I am no electrician..

As far as using these units for dynamic braking, I’m not sure that’s useful for this purpose as the mill has a manual brake and seems to have soft start built in. The lathe has an old school barrel switch, so not sure how this could help with that machine aside from a soft start feature.

thoughts?

 

For your application (same as mine), garage mill and lathe situation, in a residential setting with single phase, I really like these.
https://www.wttool.com/phase-a-mati...MI79OdyMC9_AIV1Ah9Ch0jNQoeEAQYASABEgJFwvD_BwE
A VFD would be nice, but not sure why you need it, other than to soft start it. These Phase-a-matics are small, quiet, easy to wire, and reliable. I'm going on 20 years with one.

 

That’s what I am using to start my phase converter motor to generate the 3rd leg. Since the 3 phase motor has 3 windings, when the capacitors discharge, that third winding generates the third phase to give , more or less, full 3phase power to the machines.

Therefore a static phase converter will only allow a 3 phase motor 2/3s of the rated HP output.

A. Variable frequency drive can be programmed for soft start and dynamic braking while automatically switching the electric phases to match the windings of the motor, or so I surmise, to allow full HP output of the motor.

It’s beyond my present skills to measure the phases to ensure my radial converter is working correctly and supplying proper power.

 

This actually clears up a lot of stuff for me. I now know why what I did works and works correctly.

it also cleared up the specific differences between delta, why and delta wild leg stuff and how I can pull off one hot lead on a machine to power a mag starter running a 120v coil. I know it works, but now it’s more clear as to why.

 

I have a VFD on my mill and love it. Dial up or down for the perfect speed. Run in reverse.
https://dealerselectric.com/variable-frequency-drive-motor-control.asp

 

If I had speed change via belt like my old mill, I would be all over this. Likewise if my lathe was not variable speed I would get one for sure.

For safety, maybe dynamic braking for my old lathe might be a selling point.

 

I have seen these running, had explanations on the magic but never could get a grasp.....thanks for clearing things up...a little......way over my pay grade

 

I thought maybe where Chris was going with this is VFD's used to make 3 phase from single phase. Eliminate the rotary converter. I have been seeing jobs with big hvac units showing up with 3 phase motors and VFD that converts their single phase to 3 phase at the VFD. I thought that would solve a lot of our problems in a small package.

 

Yeah, thats exactly the thought. I was worried that the radial phase converter was creating the wild leg where teh wave form was messed up, but I read some wrong info. I was just hoping it worked and it did, but that video cleared it up for me in that respect.

The 220 is "single" phase, but not really since its 2 hot legs. All the old 220 dryers and what not dont use a neutral, so my junk is delta with a wild leg. I just went with the same principle and didnt burn my house down.

However, I am looking to make things a bit more modern and not use junk I literally found 15 plus years ago to power my stuff for over 10 years with no upgrade.

So, here's another question... A welder on a variable frequency drive? It seems this application would be amazing to soft start a giant 3 phase air compressor on not enough house juice..

 

220-240 is single phase.(2 -120 legs 180* apart). Neutral doesn't have anything to do with it. Not sure about the welder idea. Why would you need it, unless you had a 3ph welder for some reason. Soft starting a compressor is where a VFD would shine. That would be awesome, not having the big across the line inrush.