PowerFlex 525 Payoff Analog Sensor

[KonstantinKolev]

Hi,

We have a bag in box machine with a few payoffs that unroll foil. The inverters are PowerFlex 525 and the tension rollers mechanism is being moved by pneumatic cylinders - one from each side. A smc analog sensor is mounted on one of the pneumatic cylinders. The sensor gives feedback to the inverter using a current signal - 4 - 20 mA and there is a digital output signal that runs the inverter.

The logic is as follows when the machine is pulling foil the cylinder of the the foil tension rollers mechanism are retracting therefore they give feedback and a run signal to the inverter to run and unroll some amount of foil. There is a hysteresis zone on the sensor that gives the current signal according to the current position of the cylinder piston.

The sensor feedback signal goes in as a process value for the PowerFlex 525 internal PID that controls the frequency of the inverter. The frequency setpoint is in a parameter - A464 for PID 1.

The problem is that after 10 machine cycles or more, approximately 4.4 seconds each cycle, the payoff inverter gives an error - F006 - Motor stalled.

This behavior is observed when the foil roll is getting small i.e. 20-30% of the initial amount.

Best Regards
Konstantin Kolev

 

[kekrahulik]

The fact that you say it happens when the roll gets smaller makes me think it is a speed issue since a smaller diameter needs to rotate faster to achieve the same surface speed.

Watch the drive output frequency from start to fail. What range are you seeing? What is the maximum frequency of the drive? Any chance you are going faster than 60hz and losing torque?

 

[KonstantinKolev]

The fact that you say it happens when the roll gets smaller makes me think it is a speed issue since a smaller diameter needs to rotate faster to achieve the same surface speed.

Watch the drive output frequency from start to fail. What range are you seeing? What is the maximum frequency of the drive? Any chance you are going faster than 60hz and losing torque?

The maximum allowed frequency in parameter P044 is 100 Hz and the PID setpoint in parameter A464 is 35%.

I tried changing the maximum frequency to 60 Hz and the PID setpoint to 10% but after 12 cycles the payoffs with small foil rolls gave the same error - F006.

 

[kekrahulik]

So the next thing I would look at is your motor FLA and the drive overload current. Watch the current as it cycles. Any chance the drive current is running high and the drive is going into torque limiting?

 

[KonstantinKolev]

The key here was the run signal to the PowerFlex525. As the signal was read from the analog sensor digital output the F006 error appeared a lot.

Now the signal is given from the PLC as it reads the analog value from the analog sensor via the PowerFlex525 parameter reading and gives a run signal respectively to each inverter with respect to its analog sensor.

The machine has been working quite some time and NO error appeared yet.

Best Regards
Konstantin Kolev