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Mode of Tripping

A number of factors arise in choosing a circuit breaker to protect against overloads and short circuits. E-T-A specialists can advise on your requirement, according to the specific field of application. Four types of tripping operation cover most situations.

Thermal Circuit Breakers (TO)

The tripping mechanism comprises a thermal actuator and mechanical latch, designed to discriminate between in-rush/ temporary current surges and prolonged overloads to ensure effective overcurrent protection. Applications include motors, transformers, solenoids and low voltage wiring.

Thermal-Magnetic Circuit Breakers (TM)

Combining a solenoid in series with a bimetal thermal actuator, these provide time/current characteristics with two distinct steps. A high overcurrent value causes the solenoid to trigger the release mechanism rapidly, the thermal mechanism responds to prolonged low value overloads. These circuit breakers are well suited to telecommunications, process control, and similar applications requiring precision performance.

Magnetic Circuit Breakers (MO or HM)

A well-proven design of solenoid coil with optional hydraulic delay provides tripping that is highly tolerant of changes in ambient temperature. A wide range of performance characteristics is available in single, double and three pole configurations.

Serie 808 is a fast acting magnetic device sensitive to small overload currents. Typical applications include printed circuit board and power semi-conductor protection.

High Performance Circuit Breakers

Where ultimate operation under adverse conditions is required, E-T-A high performance circuit breakers provide high interrupting capacity and excellent environmental specifications. Available in thermal and thermal-magnetic versions, they offer current ratings up to 500 A. Special models are designed for aerospace, defence and similar heavy-duty applications.