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QM1SD Switch-disconnector

The QM1SD switch disconnector derive from the 3SM8N molded case circuit breaker, so they have the same overall dimensions, installation and accessories. The only difference is that 3SM8G switch disconnector is not configurated with protection trip units.


Applications and functions

The QM1SD switch disconnector can be used to make and break circuits under load condition, and as isolation parts for lines, busbuars or groups of devices in sub-switchboards.


The main function carried out by switch disconnector is isolate the circuit which they are inserted in. When their contacts are open, they are at a distance which is enable to prevent arc from striking and provide safety isolation.


Due to the absent configuration of protection trip unit inside, 3SM8G switch disconnector is with no possibility to protect against overload, short-circuit and ground fault etc.
Besides, the switch disconnector must be protected on its supply side by a coordinated device which is enable to protect it against short-circuit.

Making capacity

The making capacity Icm is a very important performance to a switch disconnector, because it must be able to withstand the dynamic, thermal and current stresses which occur during closing without being destroyed, up to the short-circuit closing conditions.


The same frame design with MCCB QM2;
Complete accessories;

Technical specifications

Standard: IEC 60947-3
Number of poles: 3-pole, 4-pole
Rated operating voltage Ue:400 V
Rated insulating voltage Ui: 500 V, 800 V
Rated frequency: 50/60 Hz
Rated impulse withstand voltage Uimp: 6 kV, 8 kV
Rated short-time withstand current at 1 s Icw: 760 A to 9600 A