PowerFlex 70 Safety Circuit

I am currently in the process of designing controls for a small piece of equipment. My questions pertain to a PowerFlex 70 drive with the new “Safe Off” option. My intention is to have the safety circuit stop the PF70 drives via stop category 1 (ramp) or to have the Ethernet network stop the drive under normal stop conditions. I want to have two decel settings. One for an e-stop condition (aggressive ramp) and the other for a normal stop condition (normal ramp). I have read the various manuals for the drive and think I can do this quite easily.

1) If I remove the stop signal from terminal 1 on the drive, does this over-ride the soft comms from the network?

2) I think I need to set up a digital input to handle which decel I want (decel 1 or decel2)?

3) How does the drive know which decel to use? By changing the digital input from 0 to 1?

4) There is also ownership issues that I do not completely understand. If one source has control presently, the manual says it must release control before another source can issue a command because the decel parameter is exclusive. How do you get the first source to let go of command?



Thanks in advance for the feedback!

It is my understanding that the safe off option will allow you to designate an input that electromehcanically (itty bitty force guided relay?) enables the gate firing circuit of the IGBTs. So, if you remove the safe off input, the motor can only coast to a stop.

If you wish to ramp stop aggressively on e-stop, use an external safety relay with off delay contacts to open the safe off input after a predetermined delay which will be the maximum time you are willing to allow the drive to decelerate the load.

Use the safety relay immediate contacts to open the input to the ramp stop signal and turn on the 2nd decel input.

The safe off option avoids having an external contactor for safety in certain categories, but results in a coast stop, but a more guaranteed one than in a drive where the inputs are subject to software interpretation.

Be sure to inform the end users of these drives that if they must replace a drive, they will need to move the safe off option module to the replacement, and I think there is a jumper that must be pulled...

Paul

That's how we do it anyway...

Paul,


You are absolutely correct. I ran into this at a customer site on a MCC changeout. The electricians and other Controls guys on site had no idea about the Safe Off option board. I have the same understanding from you on the operation of the safe off feature. I noticed that the drive was displaying Not Enabled and did some research (at 12:00am in morning) to come up with the same answer you gave.

David

If you wish to ramp stop aggressively on e-stop, use an external safety relay with off delay contacts to open the safe off input after a predetermined delay which will be the maximum time you are willing to allow the drive to decelerate the load.

Click to expand...

If you are going to use a ramp to stop for an emergency stop function (i.e. the stop category 1) then ensure that access to the moving parts is not allowed until they have stopped. Use a solenoid guard lock operated by a timed output from your safety relay. This needs to be "fail safe" so it must energise to unlock.

The stop is coast-to-stop

The powerflex wil make a coast-to-stop.

From the manual for the safe off option is this text:
The PowerFlex 70 Safe-Off option disables the drive’s output IGBT’s by disconnecting the gate control power supply. When used in combination with a second safety channel (the Enable input), the system satisfies the requirements of EN 954-1, Category 3 for safe-off and protection against restart.

Under normal drive operation, the Safe-Off relay is energized, the enable input is energized, and gate control power is available to the gate control circuit. If either of these inputs is de-energized, the gate control circuit is disabled. To meet EN 954-1, Category 3 operation, both safety channels must be de-energized. Refer to the following examples for details.

Important: By itself, the Safe-Off option initiates a coast-to-stop action. If coasting to a stop is not desired, additional protective measures should be taken.


Link to the manuel is:

Safe Off option board

Hi All,
First time to post so here goes.

David,
We have the same message "Not Enabled" displaying on the Powerflex drive and can't seem to find how to solve or get rid of it. Can you cast your mind back three years and give us an answer?

Welcome to the forum.

A bit more specific info would help in getting an answer to your question. But for now I'll assume you have a PF70. If so some basic steps to try are to ensure that pin 6 (enable) on the VFD & pin 3 on the Safe Off board have power applied.

motorcontrol said:

Hi All,
First time to post so here goes.

David,
We have the same message "Not Enabled" displaying on the Powerflex drive and can't seem to find how to solve or get rid of it. Can you cast your mind back three years and give us an answer?

Click to expand...

Hi

Have the drive been running or is it a new drive??

If old drive check the safty wiring - you find link for the manual in my old post.

If it is a new drive.
Is it a PowerFlex 70 with Safety Option?

If not with the Safety option, then check the wiring by the PowerFlex 70 manual page 1-17.
If wiring OK folow the start-up guide in chapter 2 in the manual

Link for the PowerFlex 70:
http://literature.rockwellautomation.com/idc/groups/literature/documents/um/20a-um001_-en-p.pdf

Hi,
Thanks for welcome and the prompt replies.

Yes it is a Powerflex70 with safety option and a new installation.
We have followed the connection diagram using the Minotaur MRS9T

The drive is in a remote location so popping out to site is difficult to check on wiring, but the more info before we go to site is appreciated.