Resetting motor rotation protection.

Questions & AnswersCategory: Air Compresser TroubleshootingResetting motor rotation protection.
Matthews asked 1 year ago

Our Atlas copco air compressor shutdown this morning,  showing a fault of motor rotation protection triggered. We have tried to reset according to Atlas copco procedure but it’s failing to reset. 

When we press the start button, the elektronik display screen shows the machine has started running. We can hear the relays engaging but contactors are not energising. After few seconds after the timer engages the Delta contactor, the machine shutdowns and shows an error

We have checked the wiring and seems ok, the phase sequence is also okey. What could be the problem? How can we reset the machine? 


2 Answers
Cas Staff answered 1 year ago

Hi Matthews,

Generally speaking, there are two ways that ‘rotation protection’ is ‘fitted’ into machines:

  1. Phase sequence relay
  2. Checking for output pressure with a time limit after start.

You seem to have a phase sequence relay, but it could also be that the error on the Electronicon comes up because no pressure builts up x seconds after startup.

In fact ‘rotation direction/error’ is an error message that comes up on many machines (different brands/models) when actually, the problem is that the motor just is not running at all.

To find the problem, you will need to check the Electronicon outputs and see if power reaches the big contactors.

As a protection, the control power to the star contactor is usually fed through an auxiliary connection on the delta contactor, and the other way around – to make sure that they never ever engage at the same time.

So please check those auxiliary contacts as well.

Do none of the contactors engage? That’s a bit strange – it could be a problem with the power source towards the contactors (the control power). Are the big contactors controlled directly from the Electronicon (most probably) – it could be the supply power for the digital outputs that is bad (broken wire, bad connection, fuse blown).

Hope this was helpful 🙂 Don’t hesitate to ask anything. Let me know how it goes.

Good luck!





Nsikak answered 8 months ago

Hi Atlas copco(Admin), I just have this same issue this morning with my GA45 model. The machine is starting with all contactors engaging at precise timing, but the machine is not loading but will shutdown few seconds after changing to Delta with Motor rotation protector triggered.

Please what is the likely root cause of this problem. The phase sequence is correct and the motor direction is also correct.

Thank you