A fail-safe device is provided for use with a thyristor having a main body sandwiched between electrically conductive end plates. The fail-safe device includes a spring body formed of electrically conductive material having contact surfaces bent about a central fold. The thyristor is placed between the contact surfaces with the end plates in electrical opposition to each contact surface. A conductor plate is disposed between one of the end plates and one of the contact surfaces. The conductor plate includes a lead for electrical connection to the circuit to be protected. The spring body includes a lead for electrical connection to an electrical ground. A dielectric spacer is disposed between the conductor plate and the contact surface. The dielectric spacer is selected to deform in response to an elevated temperature generated by the thyristor during an over-voltage condition.
