Circuit Breaker

Three-phase circuit breaker controlled by external signal


Switches & Breakers


The Circuit Breaker block models a three-phase circuit breaker that uses an external signal and phase current information to break an electrical circuit.

The table shows how the external signal vT controls the block behavior.

ConditionBlock BehaviorResistance Parameter Used
vT < ThresholdThe breaker is closed. Each phase in the composite three-phase port ~1 connects to the corresponding phase in the port ~2.Closed Resistance
vT Threshold

When the current in any phase of the composite port ~1 crosses zero, the phase disconnects from the corresponding phase at port ~2. The breaker is open.

Open Conductance


Closed resistance

Resistance between ports ~1 and ~2 when the breaker is closed. The default value is 0.001 Ohm.

Open conductance

Conductance between ports ~1 and ~2 when the breaker is open. The default value is 1e-6 1/Ohm.


Threshold voltage for the control port vT. The block uses the threshold voltage and the value of vT at the start of the simulation to determine whether the breaker is initially open or closed. When the voltage rises above the threshold, the breaker opens each phase as its current crosses zero. When the control port voltage falls below the threshold, the breaker closes. The default value is 0 V.


The block has the following ports:


Expandable three-phase port


Expandable three-phase port


Scalar control port, which is either a physical signal or an electrical port.

Introduced in R2013b

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