Case 3: Precharge inhibit for electrical work under 24 V voltage supply

The line contactor K3 is closed or opened by the supply and regenerative module via the coupling relay K1 according to technical requirements. Additionally, the PLC can open the line contactor K3 via the coupling relay K4, e.g. in an emergency.

If the PLC opens the line contactor K3 via the coupling relay K4, but the 24 V voltage supply remains active and electrical work is to be performed on the inverter, motor cables or motor in this state, then precharging of the DC link must be prevented via the coupling relay "precharge inhibit K2".

The precharge inhibit disconnects the internal ground connection of the DC link precharge circuit on the supply and regenerative module via contacts X13:PCE and X13:GND. Precharging is then no longer possible.

K1	Coupling relay for line contactor K3
K2	Precharge inhibit
K3	Line contactor
K4	PLC coupling relay for line contactor K3