
MANUAL MOTOR STARTER GUIDE
APRIL 19
21/80
2.3 Switch and breaker types
Below is a description of the devices for the correct selection, these are applicable for the manual motor starter:
−
Motor protection circuit-breaker
−
Circuit-breaker
−
Load Switch
−
Disconnect switch
2.3.1 Motor protection circuit-breaker
Usually this means a device especially for the overload protection of motors. In smaller current ranges the motor pro-
tection switch often serves directly as a manual operation switch. In its original form, it only had a low short-circuit
breaking capacity. Today, the term motor circuit-breaker is also understood to mean a circuit-breaker with motor
protection characteristic
2.3.2 Circuit-breaker
The circuit-breaker is a mechanical switching device that can switch on, conduct and switch off currents under oper-
ating conditions in the circuit, and can also switch on under specified exceptional conditions, such as a short-circuit,
for a specified period of time, and switch off (IEC 60947-1).
2.3.3 Load switch
The load switch is a mechanical switch that can switch on, conduct and switch off currents under normal conditions
in the circuit, including a specified operational overload, and can also operate under specified exceptional condi-
tions, such as short circuits, for a specified period of time.
A load switch may have a short circuit breaking capacity but does not need to have a short circuit breaking capacity
(IEC 60947-1). Short-circuit currents can be conducted (high short circuit resistance), but not switched off.
2.3.4 Disconnect switch
The disconnect switch is a mechanical switching device that in the open position meets the requirements specified
for the disconnection function (IEC 60947-1). The disconnection function is to switch off the power supply to the en-
tire system or part of the system, whereby the system or part of the system is disconnected from any electrical
energy source for safety reasons. Important here is the opening distance. The electrical separation from pole to pole
and from input to output must be ensured, this is realized by a visible disconnection point or the device-internal (me-
chanical locking device) by appropriate constructive measures.
A device fulfills the isolating characteristic according to IEC 60947-1 if, in the "open" position, it ensures an isolating
distance in which the specified dielectric strength between the open contacts of the main circuit of the switching
device is fulfilled. It must also be equipped with a display device with respect to the position of the movable contact
pieces. This switch position indicator must be securely connected to the actuator, which may serve as a switch posi-
tion indicator, provided that it can only indicate the open position in the "released" position when all movable
contacts are in place the "open" position.
A disconnector must be able to open and close a circuit only when either a current of negligible magnitude is turned
off or on, or when there is no appreciable voltage difference between the two terminals of each current path. Devices
fulfilling the “disconnecting function” Are marked in the front with the following symbol: