Remark 4: Warmstart

The parameter Warmstart allows to the set the behavior of the CPU in case of

  • severe errors (class E2) and
  • short voltage dips (only variants with 24 VDC supply)

If the default setting is used, the CPU changes to STOP mode if a severe error occurs. The CPU is switched off for voltage dips >10 ms. The display shows AC500.

The new settings allow performing a warmstart of the CPU after a severe error or after short voltage dips or in case of both events.

Note

The parameter Warmstart after E2 error takes effect not before the configuration data of the project has been evaluated. If an E2 error occurs prior to this, it will be recorded into the diagnosis system, but no restart will be performed. The intention of this parameter is to raise the availability of the PLC during running mode (RUN) when non-systematic E2 errors occur.

The following figure shows the behavior of the CPU for different control voltage signals.

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Short voltage dips, i.e., the control voltage falls below a value lower than “Powerfail OFF” (<11 VDC) for less than 10 ms, are bridged by the PLC, i.e., the CPU remains on.

If the control voltage is switched off, the CPU remains on for > 10 ms.

If the control voltage is lower than 11 VDC (but > 6 VDC) for longer than 10 ms and then goes back to the normal value, the behavior of the CPU depends on the setting for the parameter “Warmstart”. If the parameter is set to “Off”, the CPU remains in power fail mode, i.e. it does not restart. A restart of the CPU can only be done by switching the control voltage OFF/ON. If the parameter is set to “On after short voltage dip” or “On after E2 or short voltage dip”, the CPU is restarted when the control voltage is greater than 17 VDC for 5 seconds. However, if the control voltage falls once more below 11 VDC within these 5 seconds, the time is restarted. Thus, the control voltage must have a value > 17 VDC for 5 seconds.