Why do I receive incorrect results using the Breaker block from the Elements Library in SimPowerSystems 4.2 (R2006a) while simulating a DC circuit?

I replaced the AC source with a DC source in the "power_breaker" demo model. However the Breaker block does not yield the right results.

I do not expect any output current while the Breaker is open, but I see a constant DC current at all times.

Answer 1

[MathWorks Support Team]

Documentation on the Breaker block from the Elements Library in SimPowerSystems 4.2 (R2006a) is not clear about the use of DC sources.

Here is some additional information on the use of the Breaker and Ideal Switch blocks:

The circuit breaker in SimPowerSystems opens/closes at a zero current crossing. This may not be the best solution for DC circuits. Instead, use an Ideal Switch and set the parameters of the Ideal Switch the same as those for the Circuit Breaker.

The Breaker block is not unusable for DC circuits. As the first line in the documentation for this block indicates, the breaker opens (after being initially closed) only on current zero crossing. Even in a DC circuit, if there were current direction changes or any reason for a zero crossing, the breaker would function correctly.