Overvoltage protection circuit

An overvoltage protection circuit for protecting the electronics of a motor, in particular of an EC motor, against overvoltage pulses, the overvoltage protection circuit comprising:

• two protective devices (FS1, FS2) which are arranged in series connection between two connections, wherein a resistor (R1) or (R2) is connected in parallel to each of the protective devices (FS1, FS2) and at least one capacitive element (C1) is provided in parallel connection to the first protective device (FS1), wherein the overvoltage protection circuit has, between the connections, at least a first lower and a second higher breakdown voltage point at a voltage UZ1 or UZ2 dependent on the voltage change over time k=(dU/dt) of a voltage UGA at the connections, wherein each protective device (FS1, FS2) has a voltage-dependent resistor and is insulating below a respective protective device-specific breakdown voltage and, respectively, is conductive above the corresponding breakdown voltage;
• wherein the protective devices (FS1, FS2) are designed as gas discharge tubes, overvoltage arresters or varistors;
• wherein in the case of a rapid voltage change of the voltage UGA to the breakdown voltage UZ1, wherein, if k is greater than a system-specific value kspez, at least one of the two protective devices (FS1, FS2) becomes conductive or an electric arc is ignited;
• and
• wherein in the case of a slow voltage change of the voltage UGA, wherein, if k is smaller than a system-specific value kspez, one or both protective devices (FS1, FS2) become conductive only when the second higher breakdown voltage UZ2 has been reached or an electric arc is ignited in at least one of the protective devices (FS1, FS2).