Frequently asked questions
How does a thermal magnetic trip unit work?
29 September 2021Issue:
How does a thermal-magnetic trip unit work in a circuit breaker?
Miniature and Molded Case Thermal-Magnetic Circuit Breakers
Thermal magnetic trip units trip under short circuit conditions instantaneously, with no intentional delay. Below the instantaneous trip current, they have a delay established to protect conductors while allowing momentary current surges such as for motor starting and transformer inrush. In some cases, they have adjustable instantaneous trip current settings.