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Entry type: FAQ Entry ID: 21899020, Entry date: 08/22/2005
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Why is the querying of the output control interface EVS of the installation driver not sufficient to determine whether a drive has stopped?

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Description:
EVS is designed as a link signal for interlocking with other drives or as a check-back signal to the path or to the group, and not as "Motor running" signal. Therefore EVS=0 is possible, even if the associated motor is running, e.g. in on-site mode or in the case of a drive fault.

Behavior of the output control interface "EVS link signal"
1 signal means "Drive is running" error-free in automatic mode or in single start mode.
Mainly used for interlocking with other drives and as a check-back signal to the path or to the group.

If the motor is defective or is running in on-site mode, EVS is always 0.

EVS=0 alone is also not sufficient for querying "Motor in STOP".
If "Motor in STOP" has to be determined exactly, then you must include the hardware input check-back signal (ERM) and any speed monitor signal.

In the case of a "sticking contactor" fault, after switching off of the E block (e.g. through EBFA), the motor would continue to run despite EBE=0, due the hardware fault (recognizable by ERM=1) - because of the error situation you would have the signals EST=1 and EVS=0.

Example:
If now, assuming EVS=0, an associated auxiliary unit (lubrication ...) that is to supply the motor running in a defective state, were to be stopped, this would be exactly the wrong response.

Note:
The behavior of the EVS signal was already like this in the previous versions.


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