A mechanical switching device capable of making,
carrying and breaking currents under normal conditions which may include
specified operating overload conditions and also carrying for a
specified time current under specified abnormal circuit conditions such
as short circuit.
Schematic symbol of a switch: Contactor
mechanical switching device having only one position of rest, operated
normally by ‘electromagnetic’ force, capable of making, carrying and
breaking current under normal circuit conditions including operating
overload conditions for very short durations.
Schematic symbol:Circuit Breaker
mechanical switching device capable of making, carrying and breaking
currents under normal circuit conditions and also making, carrying for a
specified time, and breaking currents under specified abnormal circuit
conditions such as those of short circuit or overload conditions.
Schematic symbol: Isolator/Disconnector
mechanical switching device which, in the open position, complies with
the requirements specified for the isolating function, (Safety!)
according to IEC specification 947 Part 2.
Schematic symbol: Note:
The isolator “function” can be added (included) in other devices - e.g.
Circuit Breaker: MCB, MCCB or ACB Power Switching
function allows any power device to be switched on or off and
sometimes, when an electric motor is being controlled, to vary the
electrical energy being supplied to the motor, in order to control its
speed or torque, etc.
Depending upon the needs of the application this function may be achieved using:
- Electromechanical products: contactors, contactor breakers, manual motor starters.
- Electronic products: solid state contactors and relays, “softstarters”, variable speed drives.