Powerflex 525 doesnt start

Hello All,

I have Powerflex 525 drive running over Ethernet IP. The system is running for quite some time. Every now and then we have a strange issue. When the start command is given the drive doesn’t move. I have the checked the drive paramters the commanded frequency is 50 hz but output frequency and voltage is 0.I have checked voltage across terminal 1 it has 24v dc and also the control status bit 1 confirms that. I have checked 24 V dc at s1 and S2 terminals. The only way to run the drive is toggle safety input of s1 and s2 and the drive runs. What could be the reason. Kindly advice

Check your logic to see what sets the STOP command.

It is common for people to program A-B drives so that STOP is asserted whenever the START command is not asserted.

The problem is that the communications is asynchronous to the logic scan. If the I/O timeout happens in between instructions that control those bits, then both the START and STOP bits are sent to the drive with TRUE values.

In such a case, "STOP wins", and the drive won't start. The Stop bit must be false before the Start bit goes through a false-true transition.

The fix is easy: program the STOP bit to only be true until the Active bit is false. That stops the drive without holding the Stop bit true.

That might not be your problem (especially because the safety circuit appears to be involved in your system) but it's common enough that you should check it out.

Thanks Ken. Actually we are using addon instruction for the drives .I have attached the screenshot

Try placing a "drive active" bit in front of that stop command (you only need to tell the drive to stop if it is running). See if that doesn't fix it.

(what Ken said)

Thank you for posting that screenshot !

That is the simple logic that causes the effect I was describing.

I also will put a Drive.Active XIO in front of the Start command. This will only allow the start command to the drive to work when the drive is not active. After the drive is running the command is not sent. Something I learned from Ken!!