A circuit breaker includes a short-circuit trip and an overcurrent trip. The short-circuit trip has a trip coil, and the overcurrent trip has a bimetallic element. A first terminal of the trip coil is conductively connected to a fixed contact carrier of the circuit breaker. The bimetallic element is connected in series with the trip coil. The bimetallic element is connected at least indirectly to a first connection terminal of the circuit breaker, and the first connection terminal is connected to the fixed contact carrier by a bypass line.

An electrical protection unit A including a main conductor and, for each main conductor, a current limiter device connected in series with the main conductor to limit the current when a current or temperature threshold is exceeded, the limiter device including an element made of a material having a positive temperature coefficient, called PTC, and being capable of controlling a device for tripping the mechanism M for opening the contacts of the protection unit D, to cause the opening of the contacts of the unit when the threshold is exceeded leading to a change of state of the element between a low resistance state and a high resistance state. The PTC element includes the trip device, in such a way that this element itself provides the functions of fault current limitation and of tripping the mechanism for opening the contacts.

A circuit breaker includes a short-circuit trip and an overcurrent trip. The short-circuit trip has a trip coil, and the overcurrent trip has a bimetallic element. A first terminal of the trip coil is conductively connected to a fixed contact carrier of the circuit breaker. The bimetallic element is connected in series with the trip coil. The bimetallic element is connected at least indirectly to a first connection terminal of the circuit breaker, and the first connection terminal is connected to the fixed contact carrier by a bypass line.

An electrical protection unit A including a main conductor and, for each main conductor, a current limiter device connected in series with the main conductor to limit the current when a current or temperature threshold is exceeded, the limiter device including an element made of a material having a positive temperature coefficient, called PTC, and being capable of controlling a device for tripping the mechanism M for opening the contacts of the protection unit D, to cause the opening of the contacts of the unit when the threshold is exceeded leading to a change of state of the element between a low resistance state and a high resistance state. The PTC element includes the trip device, in such a way that this element itself provides the functions of fault current limitation and of tripping the mechanism for opening the contacts.

High voltage micro-electromechanical systems (MEMS) switches are described. A MEMS teeter-totter switch connected between two terminals of a circuit breaker can include a beam coupled to an anchor on a substrate and two control electrodes, disposed on a surface of the substrate. An electrical overstress device connected between the two terminals in parallel with the MEMS teeter-totter switch may protect the MEMS teeter-totter switch when a high voltage transient signal is applied across the teeter-totter switch.

High voltage micro-electromechanical systems (MEMS) switches are described. A MEMS teeter-totter switch connected between two terminals of a circuit breaker can include a beam coupled to an anchor on a substrate and two control electrodes, disposed on a surface of the substrate. A protective switch connected between the two terminals in parallel with the MEMS teeter-totter switch may turn on during transition of the MEMS teeter-totter switch between ON and OFF states to protect the MEMS teeter-totter switch from large currents and voltages that may flow or develop across the MEMS teeter-totter switch when the voltage between two terminals is large.