Single Phase VFD

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charlie b

charlie b

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My mechanical counterpart asked me this morning whether he can use a VFD to control a fractional HP, single phase motor. It is for a fume hood, or something like that. I have never come across this application. An Internet search revealed that things of this nature do exist, and that there are possible interferences with starting windings or capacitors. Does anyone have any experience with such things?
 
charlie b said:
My mechanical counterpart asked me this morning whether he can use a VFD to control a fractional HP, single phase motor. It is for a fume hood, or something like that. I have never come across this application. An Internet search revealed that things of this nature do exist, and that there are possible interferences with starting windings or capacitors. Does anyone have any experience with such things?
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I don't.
But a couple of points immediately spring to mind.
Capacitors on the output of variable frequency inverters are a BAD thing.
The second is why anyone would want to use a VSD on a fractional HP motor.
Wouldn't something like a pole changing motor as used on ceiling fans be a simpler cheaper option?

It isn't my area of expertise. Hopefully others can chip in.
 
Use a 3 Phase motor

Use a 3 Phase motor

I have used small 3 phase motors with single phase input.
Works good and as the motors get bigger they are cheaper.
 
There are inexpensive VFDs that operate on single phase 120 power. They produce three phase, 240 VAC output. They are easy to use. Most single phase motors are not amenable to variable speed due to starting mechanisms.
 
There are variable speed drive manufacturers (is Woods still around?) of single phase input - single phase output for small motors.
I do not know if these are PWM much less variable frequency.

You can not use variable speed controllers on most Capacitor Start motors due to the speed requirements of the centrifugal switch in the start circuit.
 
There are about 4 or 5 manufacturers of single phase OUTPUT drives, although you may find more on the web because a number of people brand label the same product from a company called Invertek out of the UK. The thing they all have in common is that they can ONLY be used on PSC (Permanent Split Capacitor) and Shaded Pole single phase motors. But since you can more easily control a Shaded Pole motor with a simple cheap voltage controller, they are pretty much relegated to PSC motor applications. But for the most part, ventilation fans tend to be one of those two types anyway.

My experience however is that if you have not already designed a system, the single phase OUPUT drives tend to cost more than the cheap and plentiful single phase INPUT - 3 PHASE OUTPUT drives and a 3 phase fractional motor. So the only reason to use one is for an existing installation. Then you have to ask why? If your goal is to save energy cost, forget it. The VFD will cost you so much that there will not be any reasonable ROI, i.e. almost 10 years on one that I investigated for a customer. But if the purpose is to facilitate air balancing, then it's legit.
 
jim dungar said:
There are variable speed drive manufacturers (is Woods still around?) of single phase input - single phase output for small motors.
I do not know if these are PWM much less variable frequency.

You can not use variable speed controllers on most Capacitor Start motors due to the speed requirements of the centrifugal switch in the start circuit.
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The old E-Trac TB Woods drives are stil around, but TB Woods got out of the electronics business a few years ago by selling that division off to a Finnish company called Vacon. Vacon has been making all of Cutler Hammer's drives for years now, but because of that they were restrictted from marketing against them for a long time. When that expired, they got back into the market by buying TB Woods mostly to get access to their distribution channel. But the old E-Trac drives are still available through them I think as their "X Series".

They never had a single phase OUTPUT drive however, but they were one of the first to offer a single phase INPUT - 3 phase output drive.
 
Jraef said:
The old E-Trac TB Woods drives are stil around, but TB Woods got out of the electronics business a few years ago by selling that division off to a Finnish company called Vacon.
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It might interest you to know, if you didn't already, that Vacon was formed by a group of people who left ABB* - I seem to recall that they were a bit unhappy with ABB.
Anyway, Vacon make good kit - and no, I don't work for them. But one of my guys went to work for the UK division.

*That was in 1993.
 
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Besoeker said:
It might interest you to know, if you didn't already, that Vacon was formed by a group of people who left ABB* - I seem to recall that they were a bit unhappy with ABB.
Anyway, Vacon make good kit - and no, I don't work for them. But one of my guys went to work for the UK division.

*That was in 1993.
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Yes, I did know that about Vacon, I was with ABB right before that happened, still had connections when it did. They make a decent drive, I have no beef with them at all.
 
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