PowerFlex755 is running always with the same Frequency

[MatthisJosewski 0]

Hello guys,

I am new to this forum and have some problems with my PowerFlex755 EENET frequency inverter.

I want to do a point to point positioning task but my problem before I can have a look at the point to point positioning is, that the inverter is always running with 5Hz as soon as I give the start command. Even if I write 0.0 to the reference the output frequency is about 5 Hz. When I change my reference speed to 10.0Hz the output frequency is 12.X (see attached screenshots). . I thought that maybe a min frequency of 5Hz was set somehow, but I couldn't find a parameter and that wouldn't explain why I have 12.X Hz as the output frequency with a setpoint of 10Hz.

And an other question, have someone experience with positining tasks with a PowerFlex755 and Point to Point positioning? I think in the first step it is not working because of the problem I described above, but maybe someone have a programming example or could tell me where I can find some information about how to use the Point to Point positioning?

 

Thank you for advice! 

Matthis Josewski

Edited 28 March by MatthisJosewski

[ElectronGuru 81]

• Port 0, parameter 571 is "Preset Speed 1" and its default value is 5. Since this sounds like a new installation, it's a fair bet that value hasn't been changed. Check the rest of your configuration to see if any of the drive's pre-set speeds are active. 
• One of the first thing I do when troubleshooting speed control problems is put the drive in manual and see if it will respond properly to speed commands from the HIM. If so, the problem is likely somewhere in the drive configuration or Logix code. Sometimes I find that someone else has already put the drive in manual, and that's actually the problem.

Assuming the drive runs properly from the HIM and we therefore suspect drive configuration issues, check the following:

• What is the Speed Reference for the drive set to? This should be Port 0, parameter 545, "Spd Ref A Sel", and the default is Port 1, the HIM. If your intent is to control speed commands from a Logix controller on Ethernet, the "Internal Value" column of this parameter should be set to 877, which is "Port 0: Port 13 Reference".
• Start the drive from its normal start/stop/speed-reference source and while it's running, check Port 0, parameter 935, "Drive Status 1". This is one of the best ways to see what the drive thinks it's doing, and you're looking to see if the drive thinks it's accelerating, at speed, at limit, etc. Sometimes a current limit that should've been set to 10 gets accidentally set to 1.0, and the drive hits this limit and can't accelerate past it. In this case, the current limit bit in parameter 935 would be true, and you'd go check what the current limit is set to. (In my opinion, parameters 935 and 936 are amazing PowerFlex 750 drives troubleshooting tools).
• Because you're running at a fixed speed and the drive is not hunting for its speed reference setpoint, the problem is not likely to be in the motor control options but if you haven't found it in the suggestions above, it's worth taking a look at. Start with Port 0, parameter 35, "Motor Ctrl Mode", which decides what kind of motor is wired to the drive and how it might give feedback to the drive. Volts per Hertz would be open loop control, Flux Vector would be closed loop, is it an induction or permanent magnet motor, etc. If these are not set properly to match the actual motor, speed control problems are almost a certainty. Again, not likely here for your symptoms, but worth looking at if you're not finding the problem elsewhere. 

Hope this helps. 

[VFD Guy 13]

In my opinion, the first thing should be to determine if the drive is doing what is told. Compare the commanded speed to the output via its parameters. If they don’t match, use 750-pm001 manual block diagrams to see where the problem is. Divide and conquer