Powerflex 753 slowing conveyor at high speeds

Jasondelane · Apr 4, 2022

I have a powerflex 753 22 amp drive running a 15 hp motor, powering a short conveyor. At a commanded speed of 60 hz the conveyor is running 1200 fpm. I'm having no trouble running the conveyor upwards of 105 hz. The problem occurs when I command a speed of around 110 hz, or 2200 fpm. The conveyor oscillated between 100-110 hz. It says accelerating on the HIM, and does not seem to be in current limit and does not overload. The motor is pulling right at 20-22 amps.

Changing from induction SV to V/HZ makes no difference.

Max speeds are all around 120 hz so it doesn't seem to be limited there.

Feedback is open loop and I've static tuned the motor.

It's almost as if there's a "phantom" load on the motor when I approach 2200 fpm.

jraef · Apr 4, 2022

Once you go over 60Hz, the drive is operating in "constant HP mode", meaning the HP stays the same, but torque starts to decrease. If your load torque requirement does not, then you are going to run into this problem. So basically, your motor (and drive) are too small to be able to run over speed like that.

Once the drive hits the limits of its amp rating, it will automatically go into current limit and override the commanded speed to keep running rather than turning itself off. You can change that, but that means having it shut down. Parameter 420 is what controls this action, the default setting is a "3" for both reducing the current limit AND reducing the PWM to attempt to keep the drive running. If you change it to "0" for disabled, the drive would trip on Drive overload.

jdbrandt · Apr 5, 2022

jraef said:
Once you go over 60Hz, the drive is operating in "constant HP mode", meaning the HP stays the same, but torque starts to decrease. If your load torque requirement does not, then you are going to run into this problem. So basically, your motor (and drive) are too small to be able to run over speed like that.

Once the drive hits the limits of its amp rating, it will automatically go into current limit and override the commanded speed to keep running rather than turning itself off. You can change that, but that means having it shut down. Parameter 420 is what controls this action, the default setting is a "3" for both reducing the current limit AND reducing the PWM to attempt to keep the drive running. If you change it to "0" for disabled, the drive would trip on Drive overload.

This. Also, look at the motor nameplate. It will have a frequency range (typically 60-90) where an inverter-duty motor can still operate.

Powerflex 753 slowing conveyor at high speeds

Jasondelane

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jraef

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jdbrandt

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