Skip to main content

Kollmorgen Support Network

To better serve our Kollmorgen users with questions too complex to be addressed in this space, we made the painful decision to close this Community forum.

Please submit your question using the contact us form to reach our application engineering team.

For the immediate future, you can still access and read past posts.

Thank you for understanding and for participating in the community over the years.

F602 STO Fault Help | 28 Jun 2017 | |

F602 STO Fault Help

Hello, Im Hafiz Alsree working on final-year project about development of counterbalance mechanism for aerospace application in Nanyang Polytechnic.

I have an AKM3e servo motor to pull a load (Elevator application) with AKD-P00306-NBAN-0000 servo drive model.

Problem: Received fault F602 (Safe torque off).

Description: After power on the whole system, AKD has display code of "n6, n0, n2". After initializing settings on NI MAX and enabling Kollmorgen Workbench, AKD display code show "F6, F0, F2".


Hardware used: 

AKD3e servo motor


UMI 7772 (National Instrument)

NI 7340 (National Instrument)




Kollmorgen Workbench


Please assist and advice.

Thank you.


Hafiz Alsree

Comments & Answers

jcoleman02 said ...

jcoleman02 |
The F602 fault will occur whenever the drive is attempted to be enabled and the STO is off (low, or open circuit).  If the drive is enabled and then you drop the STO, it will fault.  If the drive is disabled and the STO is off, and then you try to enable the drive, it will fault.  The STO must be on (high) in order to enable the drive.

Hafiz Alsree | Thu, 06/29/2017 - 04:12

Thank you very much for the explanation.
It seems that the software (Kollmorgen Workbench & NI MAX) cause STO to be off.
What could be the cause of this?
Also, I assumed that limit switch is the cause as the motor position could be over limit but after trying to fix it, it still does not work.

Please advice and assist.
Thank you.

Joerg Muslewski | Thu, 06/29/2017 - 07:48

The "Safe Torque OFF" (STO) function is controlled by digital input X1:3. The workbench displays the state of this input only.
Please refer to" and to the AKD Installation Manual ("…;) for further details. There you will find the information, how to connect the input and for what it is used.

jcoleman02 | Thu, 06/29/2017 - 20:01

The state of the STO is controlled only by hardware. When 24VDC is applied to the STO input, the STO will be on. When voltage is removed (open circuit), the STO will be off.

Hafiz Alsree | Thu, 07/06/2017 - 04:24

So 24VDC have to connect to STO input.
But if I want to use the STO output, I have to connect it to a safety relay switch? Is this the only way to use STO output?

jcoleman02 | Thu, 07/06/2017 - 13:11

The AKD doesn't have an STO output. I'm not sure what you are referring to.

Hafiz Alsree | Fri, 07/07/2017 - 02:26

@jcoleman02, my reply is above at the Answers with pictures.
Thank you.

Hafiz Alsree said ...

Hafiz Alsree |



The X1 3-pin connector is this:

Is this the STO output (Suppose to connect to STO input on X1 3-pin connector)?

If not, what is that for? Or it has nothing to do with STO?


Also, I have connected it to STO input and it has F602 fault.

But when I connect 24V DC to STO input, theres no F602 fault.

jcoleman02 | Fri, 07/07/2017 - 14:58

Hafiz, I'm sorry, I still don't know what you mean by "STO output." The AKD drive does not have an STO output. The STO is an input. The STO must be supplied with 24VDC in order to be able to enable the drive. If the STO is off and the drive attempted to be enabled (both hardware and software enables are turned on), then the drive will fault with F602.
The intent of the STO is for a redundant, safety rated means of disabling (or locking out) the AKD drive. Proper operation is to first disable the drive with the hardware enable and then turn off the STO to put the drive into a safe state. The STO is not intended to be used to enable/disable the drive.

Hafiz Alsree | Tue, 07/18/2017 - 07:13

Thank you very much, I have already understood.

My mistake was that I connect the pin shown on picture above to STO input instead of 24VDC.

But however, the connections figure of UMI-7772 to AKD Servo drive shown on picture above, shows that X1-3 pin connector to be connected to 24VDC for servo drive power supply and physically my X1-3 pin connector is not together with the whole cable shown above in the connections figure, and instead it is a pin shown in the picture above.

What is this pin for?

jcoleman02 | Tue, 07/18/2017 - 13:32

I have no way of knowing what wire is in the picture above. Why are you showing me a picture of a wire and asking me where to connect it? The X1 connector has inputs for 24VDC, ground, and STO. The 24VDC input is to power the logic of the drive (control board power). The ground is the return for the 24VDC. The STO input requires 24VDC applied in order to enable the drive.

About this Question

Hafiz Alsree