Anyone used permanent magnet motors with VFDs like ABB ACS355/ACS800

Some VFDs support permanent magnet motors. For instance ABB ACS355.

Has anyone tried using anything like this?
What VFD / motor did you use?

Thanks,
Pete

I assume that you are talking about 3 phase permanent magnet motors
Yes it has been done I don't know about ABB but Yaskawa has a setup just for that.
If I remember correctly they have a default setup for that type of motor.
Check with them.

The drive must be specifically capable of operating IPM (Internal Permanent Magnet) or SPM (Surface Permanent Magnet) motors, the control algorithm to operate them is much more complex and must be validated. The ACS800 is likely capable, you would need to ask them. I doubt it for the ACS355 however. Most of the low cost drives will not have that capability, at least not yet.

The only low cost drive I know of that recently released (or is about to) IPM/SPM motor capability is the AB PowerFlex 525 series. The 750 Series is already capable of it, but is not a low cost drive.

ABB says:
The ACS355 features the following motor control functions:
− Current, torque, speed and frequency limits
− Under- and overvoltage controllers
− Starting to the rotating machine
− Linear, squared and user defined U/f curves for scalar
control
− IR compensation for scalar control
− Flux optimization for energy saving
− Flux braking for improved ramping down
− Drive temperature controlled switching frequency control
− Motor noise smoothing
− Sensorless vector control for induction motors
− Sensorless vector control for permanent magnet motors
− Smooth starting function for permanent magnet motors
− PID speed controller in vector controlled mode
− Acceleration compensation
− Speed controller auto tune
− Standalone and rotating motor identification runs
− Optional speed feed back for closed loop vector control


It's also in the users manual but there is actually not much info about it.


What I'm thinking is basically this: Is it possible to use a ACS355 with a permanent magnet motor and get "servo-like" performance in non-critical scenarios?

I don't know exactly what types of permanent motors exists. The users manual says permanent magnet synchronous motors (PMSM). What is the difference between that and IPM or SPM or are those just variants?

For testing would it for instance be possible to take a regular Siemens AC servo motor (1FT6 or 1FT7 series) and not use the encoder in the motor?

What should I be looking for as an example if I want a motor that is a permanent magnet synchronous motor but without any servo feedback?

.

GaryS said:

I assume that you are talking about 3 phase permanent magnet motors
Yes it has been done I don't know about ABB but Yaskawa has a setup just for that.
If I remember correctly they have a default setup for that type of motor.
Check with them.

Click to expand...

Yes, 3 phase AC permanent magnet motors.

Thanks for the info!

I searched around and found a Yaskawa white paper called "General Purpose Permanent Magnet Motor Drive without a Speed Sensor" from 2009.
It seems very interesting.

PS. According to the white paper Yaskawa drives that are "regular" VFDs but can also use PM motors (AC) are the V1000 and the A1000.

.

Well apparently the ABB ACS355 drive can do it. So if you knew that, why ask the question?

An AC permanent magnet motor is going to be synchronous, yes. IPM or SPM is just how they are built, ie where the magnets are located inside of it. An SPM motor has the magnets embedded on the surface of the rotor, which provides the best efficiency. An IPM motor has the magnets buried deeper in the rotor, closer to the center, which makes them better for high speed applications, i.e. 200Hz and up, but increases the losses in the rotors. Most applications switching to AC PM motors are doing so for the increased efficiency so SPM is more common. But some people want them for high speed applications like spindles, so they use IPM.

As to whether or not you can use a servo motor with that, the answer would be yes, but you are going to pay for a servo motor and not get the added performance. The whole point of an AC PM motor is that it is less expensive than a servo but smaller than an induction motor for the same HP output.

jraef said:

Well apparently the ABB ACS355 drive can do it. So if you knew that, why ask the question?

Click to expand...

I only knew that ABB wrote that it should work but there is almost no info on it in the users manual. So in theory yes it should work, but the only thing I've heard from people trying to test it is that it didn't work (for whatever reasons). That's why I wondered if anyone had actually done it.

I also wondered about what kind of performance you would get. If you could do basic motion control that way.
And I didn't know enough about PM motors to know what type of motor to pair with a PM motor capable VFD.

jraef said:

An AC permanent magnet motor is going to be synchronous, yes. IPM or SPM is just how they are built, ie where the magnets are located inside of it. An SPM motor has the magnets embedded on the surface of the rotor, which provides the best efficiency. An IPM motor has the magnets buried deeper in the rotor, closer to the center, which makes them better for high speed applications, i.e. 200Hz and up, but increases the losses in the rotors. Most applications switching to AC PM motors are doing so for the increased efficiency so SPM is more common. But some people want them for high speed applications like spindles, so they use IPM.

Click to expand...

Thanks for the well written info.

jraef said:

As to whether or not you can use a servo motor with that, the answer would be yes, but you are going to pay for a servo motor and not get the added performance. The whole point of an AC PM motor is that it is less expensive than a servo but smaller than an induction motor for the same HP output.

Click to expand...

I understand. The servomotor was just to be able to run some tests as I have those laying around.

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As I understand it, the use of a PM synchronous motor with a VFD is not to get "servo-like" dynamic performance. For that you need a servo drive and motor.

The benefits of a PM motor on a VFD lie in higher efficiency and reduced steady state speed error. Eliminating motor slip removes by far the largest source of speed error in a drive/motor system.

I haven't done it myself but I have heard numerous success stories with the ACS355 on PM motors. Plus, its one of my favorite drives for middle performance applications up to 30hp so I'd be prejudiced, of course!

DickDV said:

As I understand it, the use of a PM synchronous motor with a VFD is not to get "servo-like" dynamic performance. For that you need a servo drive and motor.

The benefits of a PM motor on a VFD lie in higher efficiency and reduced steady state speed error. Eliminating motor slip removes by far the largest source of speed error in a drive/motor system.

Click to expand...

That's how it is marketed but I think you get a little bit of both just by physics. ACS355 is what ABB calls the compact choice for machine builders. I like it too .

The drawback of using induction motors for simple motion control like positioning is low speed torque. At least that's my experience so far. Newer VFDs are in general pretty good at controlling induction motors.

DickDV said:

I haven't done it myself but I have heard numerous success stories with the ACS355 on PM motors. Plus, its one of my favorite drives for middle performance applications up to 30hp so I'd be prejudiced, of course!

Click to expand...

That sounds good!

.

Vacon is used by a number of turbo blower manufacturers. These blowers use 3-phase permanent magnet synchronous motors and usually operate at 200+ Hz.

Originally posted by Pete.S.:

The drawback of using induction motors for simple motion control like positioning is low speed torque.

Click to expand...

I suspect your drive is set up in sensorless vector mode or you NOT using TENV or TEBC motors. I have had a large number of applications there I have used a TENV induction motor with a drive operating in field oriented control with a suitable encoder and achieved full torque at zero speed for long periods of time. The real question is do you need to efficiency that a PM synchronous motor can give you at lower speeds. I find it hard to believe that the cost difference between a 3-phase induction motor and a 3-phase PM synchronous motor won't pay for an encoder. But I must confess I have never looked.

Keith

kamenges said:

I suspect your drive is set up in sensorless vector mode or you NOT using TENV or TEBC motors. I have had a large number of applications there I have used a TENV induction motor with a drive operating in field oriented control with a suitable encoder and achieved full torque at zero speed for long periods of time. The real question is do you need to efficiency that a PM synchronous motor can give you at lower speeds. I find it hard to believe that the cost difference between a 3-phase induction motor and a 3-phase PM synchronous motor won't pay for an encoder. But I must confess I have never looked.

Keith

Click to expand...

Yes, sensorless vector mode. I wasn't aware that you could get full torque at low speed with an inductor motor if you had an encoder. I thought the encoder would only if you wanted real precise slip compensation.

I thought TENV or TEBC motor was just about the enclosure and cooling. Is the motor different in other ways too? In the applications I've done it is usually a fan that always cools the motor, regardless of motor speed. And I think the motors are always rated for inverter use. Usually I don't specify anything about the motors, but maybe I should.

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If you use Flux Vector control (Motor with encoder) with the correct motor selection you can run the speed down to zero at 150% torque for a very long time.

One problem I have run into with PM AC motors is that some times they lose their magnetism and the drive will try to compensate for the lose of torque by increasing the motor current and it will over heat the motor. I can tell you from experience it's a bear to trouble shoot. There is just no way to measure the magnetism in the motor when your in the field. The only fix is to either replace the motor or send it back to the factory for testing and repair.

GaryS said:

If you use Flux Vector control (Motor with encoder) with the correct motor selection you can run the speed down to zero at 150% torque for a very long time.

One problem I have run into with PM AC motors is that some times they lose their magnetism and the drive will try to compensate for the lose of torque by increasing the motor current and it will over heat the motor. I can tell you from experience it's a bear to trouble shoot. There is just no way to measure the magnetism in the motor when your in the field. The only fix is to either replace the motor or send it back to the factory for testing and repair.

Click to expand...

Yep, I just ran into that. Most of them will lose the magnetism if they get severely over heated, and once they do, there's no going back. Most PMAC motor mfrs recommend using embedded thermal sensors in the motor, such as thermistors or RTDs, rather than relying solely on the current based thermal overload in the VFD. The other thing someone warned me about, although I've never seen it, is that if you mount two PMAC motors too close to each other, or a small PMAC motor right next to a large induction motor, the magnetic fields from the other motor can demagnetize the PMAC motor's magnets. Both of these things can happen with PMDC servo motors as well, it's just that in traditional servo applications you are not usually mounting the motors in close proximity to each other or other larger motors.

I have seen the magnets come off the armature and as you said no going back and nobody stocks a spare PMAC motor so lead time on a replacement is usually very long