BeechTalk - BT - FS: Bi-Fold Aircraft Hangar Door

Username Protected · **Posted:** 26 Aug 2019, 22:53

Username Protected wrote:

Minor point, but there is no such thing as two phase. Its either single or three phase, and I've never seen a motor that can be switched between the two.
This could be a major issue for someone if the motor is three phase and they only have single phase power. I've run into this issue many times in the past in my line of work.

Actually single phase to 3 phase is pretty easy and not that expensive with frequency drives....

Username Protected · **Posted:** 29 Aug 2019, 20:57

Username Protected wrote:

Yep, or a simple rotary converter. I once saw a complete machine shop that was ran off of a single rotary converter. A 3 phase motor only needs the third phase to start, after that it will run just fine on single phase, so the shop owner used a single phase motor to belt drive a 3 phase motor. He used that to back feed the third phase to start the rest of the 3 phase motors in the shop. Worked like a charm! I would not have believed it had I not seen it with my own eyes!
I was just speaking to the part about a motor being converted from single to three phase, that something I have never seen.
Now, back to the subject at hand. I have used up my thread hijack credits for the day..

Before we leave this sidetrack, you can actually use just a three phase motor to convert a single phase supply to three phase. All you have to do is use capacitor to create a phase shift and start the motor spinning. Once it gets close to synchronous speed it will lock in and then you can connect other motors in parallel. But any rotary phase converter is bulky, noisy, and inefficient compared to a VFD.

Username Protected · **Posted:** 14 Oct 2019, 17:58

Bump!