Did I spend too much on this motor? (3 Ph Discussion and Shenanigans)

VFD will be much more expensive in this situation, yes motor size. Plus you have to derate the motor by up to 50% depending on the VFD. If you run an inverter you do not need a vfd and if this were for a press then a VFD is not needed. Plus the rotary can be used to run the whole shop if you want. It is not as easy to run the whole shop with a VFD. For a few $$ more you can purchase a CNC rated rotary and really step up. But that is a whole new can of worms.
 
I stand corrected here. Just did a quick search for a 7.5hp VFD with 220 single phase in and 3 phase out. NOT available at least at the Co I looked at. It is available in 3ph in 3ph out. They cost about the same as the rotary but you can't run them in a typical knife shop without the rotary. If you only have 110v then the highest I could find was 1.5hp. you still need to derate the motor but 1.5hp should do most things even with derated operation.
 
Ok, just in this single purchase of the motor, I have learned more in one day than I did in one year.

That brings me to some new questions:

-If I want to run a Single Phase AC motor, I don't need anything more to run it, right? Just plug it in a go (assuming "normal" conditions).
-If I want to run a Three Phase AC motor, I need three phase power, either by a converter or VFD.
-If I want to run a Permanent Magnet DC motor, then I need DC power, either by a DC controller or voltage converter, right?
 
watercrawl said:
http://dealerselectric.com/item.asp?cID=28&scID=166&PID=647

Would that work in this case? I understand what Chuck is saying, but I'm also trying to learn something here. $836 though....youch!!
Click to expand...

Yes you can go this way but as you pointed out $836 +$51 shipping to my zipcode. If you need a VFD it might be worth it. If you don't you can have a rotary delivered for $739 and if you wanted the CNC rated unit it would be $789. That is delivered!! Then you can run anything up to 5hp with ease. If it is a hard start you might need to have a kicker, just start one of your other motors and it will provide and extra kick to the power line. So what I would have done first was buy the rotary. Why I can run my mill, surface grinder, big buffer, belt grinder (single speed with step pulleys), disc grinders also single speed, power hammer, and my press if I put a 3-phase on it. with my VFD I can run all but the power hammer, surface grinder, the press, and the 5hp side of my belt. Now I have a 3hp VFD and can run all my grinders off of that with 3ph in 3ph out, so no de-rating. I wired my shop so I kick on the rotary and can start most any tool without changing anything. TO run my 3 grinders I have to just make sure the one I want is plugged in. I use the switch plug method rather than the rotary switch for multiple units. If you were to VFD every tool in the shop at an average of $400 per I would have like $3000 invested. I now have less than 1k since I got the VFD for $200. I would like to get a 5hp VFD and might end up with a 7.5 or a 10 but would not really need it with the rotary.

It is really up to you how you approach the 3-phase problem in the small shop environment. As you have found 3-phase motors are pretty cheap. Last single phase I purchased was almost $500 for a 3hp new. The last 3phase I purchased was a 5hp delivered for $150 used. Motors are pretty bullet proof and even if they do burn out they can be re-wound for a couple hundred. I will stick with the 3-phase. They even have a killer warranty. I had to have my rotary repaired and I took one phone call and I dropped it off at a local shop. 2 days later It was fixed and I was back up. Things can happen and they took care of it all. That is all I expect.
 
Don Nguyen;10657091]Ok, just in this single purchase of the motor, I have learned more in one day than I did in one year.

That brings me to some new questions:

-If I want to run a Single Phase AC motor, I don't need anything more to run it, right? Just plug it in a go (assuming "normal" conditions).So long as you have the appropriate valtage 110 or 220 to match to motor
-If I want to run a Three Phase AC motor, I need three phase power, either by a converter or VFD. Yes there again be careful when buying a VFD or rotary that you buy the correct voltage. There are a lot of 440 and up volt units out there that go really cheap. you cannot run these from your house, unless you live in an old industrial loft that retain it's commercial power
-If I want to run a Permanent Magnet DC motor, then I need DC power, either by a DC controller or voltage converter, right?Yes
 
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