Electrical components are various basic elements used in power systems for connecting, controlling, protecting, and distributing electrical energy. Their working principles vary depending on the specific type. Below are the core working principles of some common electrical components:
Circuit Breaker
Working Principle: Overload protection is achieved through a bimetallic strip (excessive current causes it to heat up and bend, triggering tripping); short-circuit protection is achieved through an electromagnetic trip unit (a large current instantaneously generates a strong magnetic field that drives the tripping mechanism). Models with leakage current protection are also equipped with a zero-sequence current transformer to detect leakage current and automatically trip.
Application Scenarios: Distribution boxes, industrial control cabinets, etc., for overall circuit control and protection.
Fuse
Working Principle: The internal fuse conducts stably under normal current; when an overload or short circuit occurs, the current rises sharply, the fuse overheats and melts, thus cutting off the circuit and providing one-time protection.
Features: Fast response, low cost, but needs to be replaced after melting.
Relays (e.g., intermediate relays)
Working Principle: A small current controls the coil to generate electromagnetic attraction, driving the contacts to close or open, achieving the switching function of low-voltage control of high-voltage. It also serves as a signal relay, contact expansion, and electrical isolation.
Core Parameters: Pull-in voltage/current, holding current, return coefficient (typically 0.6–0.7).
Thermal Relays
Working Principle: Current flowing through a heating element causes the bimetallic strip to bend, pushing the actuating mechanism to disconnect the control circuit, achieving overload protection for motors and other equipment. It has a time delay characteristic to avoid false tripping due to instantaneous starting current.
Components: Bimetallic strip, heating element, contact system, setting current adjustment device.