Faley I know what you're talking about, and so does Max, but I think you're using confusing terms. Vector and servo have never meant the same thing in any of the literature I've come across, and your job description matches mine. Servo motors and drives, yes, must be matched, finnicky bastards, and I'm glad that's why I deal more with the industrial side of things. VFDs and induction motors don't need to be matched, but some VFDs are badged with "vector" as well as some plain-jane inverter duty induction motors. Take Baldor's line of "Vector" motors: These are NOT servo motors and do NOT need to be matched to the VFD, yet they are called "Vector."

Allen Bradley Powerflex 700 is NOT a servo drive and does NOT require drive/motor matching. Sure, it has the option (option) for encoder feedback, but it's still just an industrial VFD. Allen Bradley Kinetix/Ultra line ARE servo drives, and I've never run across the word "Vector" in any literature for those.

I say all this not to educate you, as I'm sure I haven't, but in the interest of clarifying terms.

 

Quitara,
think of a single phase motor like a bicycle with only one pedal. If you sit on a bicycle sans one pedal, and your only pedal is all the way down, you can put great effort into lifting your legs up and down, but that bike isn't going to move. In order to pedal a one pedal bike, you have to get it moving first. That's what the capacitor-start type motor does - gives you an extra pedal to push against to get up to speed, and then takes it away.

With the PSC type you have two pedals, but they're only 180 degress apart when you're pedaling full speed. When you start to slow down, the pedals on the PSC bike get closer together. At some point (decreasing in speed) your two bike pedals are aligned with eachother (or close enough) so that having that extra pedal does you no good at all.

Now, enter 3 phase. With a 3 phase bicycle, you have 3 legs and 3 pedals which are always 120 degrees apart, so you can pedal as slow or as fast as you want, take off from any position you want, with as much torque as you want, any time you want. That's why 3 phase is the preferred method for variable speed induction motors.

 

Faley I know what you're talking about, and so does Max, but I think you're using confusing terms. Vector and servo have never meant the same thing in any of the literature I've come across, and your job description matches mine. Servo motors and drives, yes, must be matched, finnicky bastards, and I'm glad that's why I deal more with the industrial side of things. VFDs and induction motors don't need to be matched, but some VFDs are badged with "vector" as well as some plain-jane inverter duty induction motors. Take Baldor's line of "Vector" motors: These are NOT servo motors and do NOT need to be matched to the VFD, yet they are called "Vector."

Allen Bradley Powerflex 700 is NOT a servo drive and does NOT require drive/motor matching. Sure, it has the option (option) for encoder feedback, but it's still just an industrial VFD. Allen Bradley Kinetix/Ultra line ARE servo drives, and I've never run across the word "Vector" in any literature for those.

I say all this not to educate you, as I'm sure I haven't, but in the interest of clarifying terms.

No, Vector and Servo don't mean the same thing. The Vectors are often called AC Servo in plants with which I've worked- industry slang. I didn't write that the PowerFlex 700 was a servo drive. I thought Max wanted an example of an AB vector drive. So, I gave him one. Whenever I've worked with vector drive replacements, they were sold as matched drive/motor packages. I was an OEM rep. This was required by the manufacturers in these cases. The same manufacturers didn't require such in the case of standard inverters.

Sorry. I'm not confusing the terms. If anything, I sought to understand Max's experience for the sake of having a better line of communication.

Nonetheless, I appreciate your desire for clarification.

 

Vector drives shouldn't be confused with v/hz scalar or torque control VFD's. Vector drives are commonly called AC servo drives, they are controlled by field orientation and do, indeed, require a vector motor that is specifically matched to the drive.

No, Vector and Servo don't mean the same thing. The Vectors are often called AC Servo in plants with which I've worked- industry slang.

So can you define what it is you actually mean by Vector? Is it any VFD that has encoder feedback option?

 

So can you define what it is you actually mean by Vector? Is it any VFD that has encoder feedback option?

Are you kidding? Here, I copied this from a reply to Max "...commonly called AC servo drives, they are controlled by field orientation..." (note the word "common")

 

Furthermore strantor, I'm trying to reply to help the OP, not to pass yours or anyone else's stamp of approval.

 

Well now you kinda sound upset.

I only started down this line because you said this:

Almost forgot: Stay away from AC Vector drives, they must have a matched motor designed for vector control.

Which, without any clarification, would lead OP to rule out most of the good drives on the market (those VFDs with sensorless and/or sensored VECTOR control). If what you really meant was "Stay away from AC SERVO drives, they must have a matched SERVO motor " then I would have been 100% with you.

 

No. I meant what I said. Which is to use a standard inverter. I don't need you to tell me what I meant to say. Are you done high-jacking the thread?

 

wait a sec...

I didn't write that the PowerFlex 700 was a servo drive. I thought Max wanted an example of an AB vector drive. So, I gave him one.

Are you saying that the PowerFlex 700 is one of those type of drives that OP should stay away from? because I've commissioned many a PF700 on many a type of motor that was "whatever was laying around."

 

No. I meant what I said. Which is to use a standard inverter. I don't need you to tell me what I meant to say. Are you done high-jacking the thread?

Yes, I'm done. I realize now that you aren't "using confusing terms" as I said, you are "confusing terms," as you said. You really mean what you're saying, and you're really wrong. If I am any good at reading people, I'm betting heavily that you aren't the type to go out an reeducate yourself, so there's nothing left to say. So I'm out. I did my part to answer OP's original question back in post #22, and I've done everything I can fight you steering him in the wrong direction.

 

To recap what I was saying to the OP, in simpler terms, for qitara's sake:

1) Most of today's industrial VFD's (inverters) are PWM devices. Induction motors are ran with VFD's (PWM)- no problem. They control speed, primarily with frequency, voltage is adjusted to improve efficiency as b1u3sf4n09 noted.

Yes you can use a PWM inverter (VFD)


2) Is the pump a positive displacement or centrifugal?

3) crutschow has a good point, if your motor is series wound, a rheostat is all you need, especially when we're talking about a half horsepower motor.

4) Ignore the mention of vector drives. They were noted as discussion of the basic types of AC inverters. They're three phase and of no significance to you. Unfortunately, they added confusion. My apologies to you, qitara.

 

Again, no offense Max, but your terminology doesn't sound like 3 phase industrial. What is your background? (If you don't mind.)

My CV.
Both Electrical and Industrial Electronics graduate UK.
Main occupation Industrial electronics, including custom design, installation, and maintenance, with last 35yrs in motion control and CNC systems integration, also integrator of Mitsubishi CNC controls, last 20yrs own company.
Max.