Safely unlocking dc voltage sources

A test panel (2) for the electrical testing of test objects (4) with the help of a high electric power to be fed into it and/or drawn from it under direct voltage (UG), the test panel comprising:

• a DC-voltage bus (30) for conducting a direct voltage (UG);
• at least one energy source (12) having a first DC-voltage interface (18) for the DC-voltage bus (30);
• a plurality of test stations (20) for one of the test objects (4), each of the plurality of test stations having a second DC-voltage interface (26) for the DC-voltage bus (30) and a DC-voltage connection terminal (28) for the test object (4) concerned;
• wherein all the test stations (20), with all the energy sources (12), are connected to one another via respective second DC-voltage interfaces (26) by the DC-voltage bus (30), by way of their first DC-voltage interfaces (18);
• wherein each of the test stations (20) contains a resonance converter (22), which contains a transformer (32) with a primary side (34) facing toward the second DC-voltage interfaces (26) and a secondary side (36) facing toward the DC-voltage connection terminal (28);
• wherein each of the test stations (20) contains a PWM generator (38), which is configured, when supplied with an operating voltage (UB), to supply the primary side (34) with a PWM signal (PS) produced from the DC voltage (UG) at the second DC-voltage interface (26);
• wherein each of the test stations (20) contains a switch (44) arranged between the secondary side (36) and the DC-voltage connection terminal (28), in order to interrupt an electrical connection between the secondary side (36) and the DC-voltage connection terminal (28);
• and
• a safety control unit (46), configured in a safety condition (SZ) to disconnect the PWM generator (38) from the operating voltage (UB) and keep it disconnected and to open the switch and keep it open.