Fig. 9 Negative Example - Active Load - Beckhoff EL28 Series Documentation

Foreword
◦ No switching of loads with a separate power supply
Loads that have their own power supply must not be switched by standard terminals, since in this
case feedback via the load cannot be ruled out.
Fig. 9: Negative example – active load
◦ The control of an STO input of a frequency converter could serve here as a negative example.
Exceptions to the general requirement are allowed only if the manufacturer of the connected load
guarantees that feedback to the control input cannot occur. This can be achieved, for example,
through adherence to load-specific standards.
◦ Option 1: Ground feedback and all-pole disconnection
The ground connection of the connected load must be fed back to the safely switched ground of
the respective output terminal.
14 Version: 2.2 EL28xx-xxxx