PM Motors on gapper belts

[lcabal27]

I'm working on a design phase for a costumer and they've requested PM motors for all conveyor belts throughout the system. We have a gapping section where we'll need to adjust speeds constantly, either accel or deccel depending on the upcoming gapping.
I was wondering if PM motors will work properly for this application or a regular AC induct motor would be better.

 

[James Mcquade]

welcome to the forum.

standard motors are not rated for vfd use. i would use vfd rated motors where the speed changes. if the speed will change through out the system, use vfd rated motors, vfd shielded cables.

how far away is the vfd from the motors?
if you are using 480 volts, be aware of the line and load reactors and load filters for the motors.

hope this helps,
if i am wrong, someone please correct me.
james

 

[Steve Bailey]

AC motors with VFDs are far more prevalent than DC permanent magnet motors in variable speed applications these days. But either should work for your conveyor application unless there are special application-specific considerations.

 

[GaryS]

The new Yaskawa VFDs are designed to run PM motos
it the customer is set on PM motors that the way to go
I would encourage your customer to reconsider their choice.
I can give you better control at a much better cost using a standard motor and VFD
PM motor was popular years ago with Powertec drives they phases out when the newer VFDs came out
PM motors can lose their magnetism over time and heat they are not readily available should a replacement be needed
Moderm VFDs use counter EMF to control the motor speed to meet the setpoint much better than any PM motor can. If you need better performance then upgrade to Flux Vector drive system with them I can give to 100% torque at zero speed ( Suspend the Load) Many other feature's
Let us know how you make out

 

[Bit_Bucket_07]

AC motors with VFDs are far more prevalent than DC permanent magnet motors in variable speed applications these days. But either should work for your conveyor application unless there are special application-specific considerations.

I assumed that the OP was referring to AC PM motors. They offer excellent speed control since they run without slip at synchronous speed. They also offer very high efficiency and a smaller footprint than an equivalent HP induction motor.

https://www.horizontechnology.biz/b...-magnet-motor-efficiency-auto-electrification

 

[Zensequitur]

I assumed that the OP was referring to AC PM motors. They offer excellent speed control since they run without slip at synchronous speed. They also offer very high efficiency and a smaller footprint than an equivalent HP induction motor.
...

I too am assuming the reason the customer is specifying PM motors is the power efficiency gains. Yaskawa a few years back was really pushing Energy Savings by using SPM and IPM synchronous AC motors with their, at the time, new A1000 drives. I figure other manufacturers were marketing similar savings.

Patrick

 

[sparky66]

On a gapper, you will want servo motors (AC PM). There are some pretty abrupt speed changes needed on the gapper, and induction motors on a VFD can't perform as good as a servo motor and servo drive. VFD's on the rest of the conveyors should be good.

 

[GaryS]

I have seen many problems with the PM motors in the past. they have been around for a long time they were the standard other than DC motors
But as they age they lose their magnetism so the current draw for the same load will increase. I have seen cases where the magnet comes off the armature then you have to replace the motor. If the motor gets hot ( as in overload ) the magnet will lose some of its magnetism
I have seen cases where the client kept a spare motor on shelf so if they had a failure they would not lose production then when they went to use the spare it would not work because the magnets weakened over time. There are only a few motor shops in the US that have the ability to repair them and then only if they can get the original motor specs for the manufacture (Rarely ever happens)
you are going to get very poor performance if you can’t get the specs and set up the vfd up correctly.
I have a client then has a PM motor on a VFD and they are getting very poor performance at low speeds in their case the original drive went out and they had to replace it with a vfd it has never worked right since. Before you ask I was not the guy that replaced it. I would have replaced both motor and drive.
As I have said this before I can get better performance out of a standard motor and a good vfd than you will ever get with a PM motor. I have multiple milling machines where I replaced the servo drive and motor with a vector drive and motor and have better performance.

 

[sparky66]

I have seen many problems with the PM motors in the past. they have been around for a long time they were the standard other than DC motors
But as they age they lose their magnetism so the current draw for the same load will increase. I have seen cases where the magnet comes off the armature then you have to replace the motor. If the motor gets hot ( as in overload ) the magnet will lose some of its magnetism
I have seen cases where the client kept a spare motor on shelf so if they had a failure they would not lose production then when they went to use the spare it would not work because the magnets weakened over time. There are only a few motor shops in the US that have the ability to repair them and then only if they can get the original motor specs for the manufacture (Rarely ever happens)
you are going to get very poor performance if you can’t get the specs and set up the vfd up correctly.
I have a client then has a PM motor on a VFD and they are getting very poor performance at low speeds in their case the original drive went out and they had to replace it with a vfd it has never worked right since. Before you ask I was not the guy that replaced it. I would have replaced both motor and drive.
As I have said this before I can get better performance out of a standard motor and a good vfd than you will ever get with a PM motor. I have multiple milling machines where I replaced the servo drive and motor with a vector drive and motor and have better performance.

I have been doing motion applications for 25 years. Mostly servo, but a few VFD's. The VFD's need to be special, not just a VFD that say it can run a PM motor. Motors can lose their magnetism if they really overheat, but the rest of your observations I have not seen. PM servo motors are very reliable and will in almost all instances give better performance than an induction motor.