I've had a couple phase converters. These were the static type. They would run a motor, but not at full speed or power. They did not produce a balanced 3 phase output. A VFD takes in the AC line power, converts it into DC, chops it up, and outputs it as 3 phase AC. This is true, be it single or three phase input.
A while back, we had a rotary phase converter built for a customer. I saw it on the dock and asked what that is for. He said it was for a guy who needed to run a couple large motors for blowers. I asked, why not just use a VFD? Said he looked them up and the largest single phase input was 3 hp. These were like 15 hp. Told him that pretty much any decent VFD made today will run from a single phase source. There are a few parameters that need to be set. Some call it phase loss protection... With a VFD specifically intended to run on 3 phase, you do have to multiply the VFD size x 1.73 to run from single phase. Would have saved the customer some cash up front and in the long run in electric savings.
As far as I see it, there are no benefits using a phase converter over a VFD. Static phase converters will rob power and diminish performance, and with rotary, you have an extra mouth to feed because you have to run the motor on the phase converter too! Absolutely no other performance or efficiency benefits either. I think the VFD guy's will side with me.
If you follow the Affinity Laws for pumps, you will see that VFD's work out to an advantage.
I have to remind the guy from Square-D to get me the manual on the 5 hp drive. I am leaning that way.
You know the old saying, "If it were easy, then everyone would be doing it"!
Last edited by JKB; 04/12/13 04:55 AM.
