Current supply systems for plasma plants or plasma applications (e.g., plasma gas discharges, used in, for example, plasma etching processes and plasma deposition processes) can be located in a switch cabinet. Typically, several current supply modules are disposed in a switch cabinet, and separate current supply modules can be combined into a current supply unit, to achieve a desired output power from the unit. The combination of separate modules into a single unit may be necessary because a single supply system often must separately supply several plasma gas discharge stations of an apparatus with current. The desired output power for each discharge station can be defined by a user, and the current supply modules are cabled together by a system engineer according to the user's wishes. Therefore, the terminals of the current supply modules are connected into a neutral point on the input side of the modules as well as on the output side of the modules. Each module includes a control unit that is connected to an external control unit. A change in the arrangement of the modules that make up a current supply unit of the art is expensive, because the entire cabling must be detached and rearranged, and the control of the unit must be reconfigured. Furthermore, equipping all the current supply modules with a control unit is expensive.
An interlock circuit can be provided to the switch cabinet containing the current supply unit. The interlock circuit ensures that no dangerous voltages are present if the switch cabinet is opened or if a current supply module is disconnected at either the input or output side. Typically, one or more contactors (or “relays”) are driven by an auxiliary voltage, such that during normal operation the contactors are closed and the current supply modules are supplied with the line voltage. If the auxiliary voltage is interrupted, the contactors open and disconnect the current supply modules from all dangerous voltages and also prevent a current supply module from producing dangerous voltages.
The auxiliary voltage is looped over all relevant plug contacts and door opening switches, such that if one of the plug contacts or the switch cabinet are opened the auxiliary voltage is interrupted. The wiring of the auxiliary voltage is arranged such that, if one of the contacts on the output side of a current supply module of a current supply unit is opened, all the current supply modules of that current supply unit are disconnected from the power line supply. However, the remaining current supply modules of other current supply units are not disconnected from the power line supply. Thus, if the current supply units and their constituent current supply modules are rearranged, the leads of the interlock circuit have to be individually linked again, which is a time-consuming process and one in which mistakes are easily made.