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Motor control Panel - e-stop

David Reynolds

Good morning all, just after a wider view on this,

we have a large control panel which allows the company to test motors on. This allows the company to verify the condition of the motor after repairs. The motors are connected to the test panel by a series of sockets from 16a up to 500a outlets, the company then has test leads with the correctly selected cable for that outlet, the test cable has a plug on one end, and the other end is terminated into the motor terminals.

The test panel has a built-in Pilz safety relay which is supplied from a number of door/gate interlocks and e-stops around the test area. The safety relay controls a number of contactors within the control panel. 

The question is, once the testing has been completed, the company hits the e-stop on the HMI control screen and places a safety lock through this e-stop. Then enters the test area, removes the plug from the socket and pre-dead at the motor terminals. (the e-stops a Idec XN4E-BL404MR)

To meet EAWR and the definition of “isolation,” would you say what the company has in place is adequate? If work is needed within the control panel itself, then the 400a isolator is turned off, secured and the panel pre-dead. The plug and socket provide the disconnection and the E-stop via the safety relay provides the secure aspect?

Thanks 

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    Does the E-stop isolate all phases ? if somehow it did not, due to a contactor jamming or similar, would it be obvious ? e.g. thing are still spinning that should have stopped or lights on ?

    Given that the next step is to unplug the device under test, it is hard to see what danger might arise, without a coincidence of multiple unlikely failures.

    Certainly the air gap from a plug and socket is about as positive as isolation get - disconnected, and seen to be disconnected from  good way back.

    Unless there are other factors at work, then from what you describe the electrical risks are well managed.

    Why are you asking, has there been some sort of near miss ?

    Mike.

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  • 0

    Does the E-stop isolate all phases ? if somehow it did not, due to a contactor jamming or similar, would it be obvious ? e.g. thing are still spinning that should have stopped or lights on ?

    Given that the next step is to unplug the device under test, it is hard to see what danger might arise, without a coincidence of multiple unlikely failures.

    Certainly the air gap from a plug and socket is about as positive as isolation get - disconnected, and seen to be disconnected from  good way back.

    Unless there are other factors at work, then from what you describe the electrical risks are well managed.

    Why are you asking, has there been some sort of near miss ?

    Mike.

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