Device for protection from mains surges in a three-phase mains

The invention relates to a device (14) for protection from mains surges (U1, U2) in a three-phase mains (4), the device (14) consisting of three delta-connected active surge arrestors (16, 18, 20), the voltage-dependent fixed resistors (28, 30, 32) of which are connected to the three-phase mains (4) via thyristors (22, 24, 26) in the event of a surge (U1, U2), each thyristor drive (34, 36, 38) containing a series circuit comprising a diode (46, 48, 50), a voltage-controlled diode (52, 54, 56) and a gate resistor (58, 60, 62). According to the invention, the inputs (64, 66, 68) of the surge arrestors (16, 18, 20) are isolated from each other using isolating diodes (82, 84, 86) so that each isolating diode (82, 84, 86) is linked, on the anode side, to the input (64, 66, 68) of a first surge arrestor (16, 18, 20) and, on the cathode side, to an interconnection point (72, 74, 70) of the diode (48, 50, 46) and the voltage-controlled diode (54, 56, 52) of the thyristor drive (36, 38, 34) of a second surge arrestor (18, 20, 16). This provides a device (14) for protection from surges (U1, U2) with substantially reduced expenditure on components and a substantially reduced volume of the apparatus. <IMAGE>