Safety circuit for the explosion-proof casing and method of operating said safety circuit

Safety circuit as in one of the previous claims

• characterized in that the control unit (30) is disposed to switch the controlled switch (31) into the disconnected position (T), directly after switching on the supply voltage (UV).

Safety circuit as in one of the previous claims

• characterized in that the control unit (30) comprises a control part (39) of a relay (40).

Safety circuit as in one of the previous claims

• characterized in that the at least one capacitor (19) is a component of a voltage supply device (20).

Safety circuit as in one of the previous claims

• characterized in that the at least one capacitor (19) is associated as a starting capacitor (49) with an electric motor (47).

Method for operating a safety circuit (10) for an explosion-proof casing (12) in which is arranged an electrical operating means (11), comprising a control unit (30) connected to a power supply input (13), at least one capacitor (19), a series circuit consisting of a controlled switch (31) and a discharge resistor (32), said series circuit being connected to the at least one capacitor and forming with the at least one capacitor (19) an electrical discharge circuit (33), comprising the following steps:

• Making available a supply voltage (UV) to the power supply input (13) or making available a supply voltage to the power supply input (13), and switching or operating the electrical operating means (11) as a result of which the at least one capacitor (19) charges to a capacitor voltage (UC),
• Switching the controlled switch (31), after switching off the supply voltage (UV), into a closed position (S) in which said switch closes the electrical discharge circuit (33).