switch has no interrupting or load-carrying capability. It serves only to
provide isolation of the circuit or load by manual means after the power fl ow
is cut off by the circuit protective device.
The safety switch is a load-break switch having a quick-make and quick-break
contact mechanism. Safety switches are used in small power systems with
limited short-circuit capacity. The safety switch may be fused or unfused.
The interrupter switch is of quick-make, quick-break type and is capable of
interrupting at least 12 times its continuous current rating. They are assigned
horsepower rating. These switches are available in continuous rating from
30 to 1200 A and can be installed in switchboards, panelboards, and grouped
motor control centers. The interrupter switch may be utilized with or without
fuses depending upon the application.
Some light industrial systems or commercial buildings will use switchgear
or switchboards with a high pressure or bolted pressure, three-pole switch
acting as incoming service main disconnects. The principal feature of these
switches is their continuous current capacities of up to 3000 or 4000 A. At these
currents, very high contact pressure is required on the conducting surfaces in
order to hold temperature rises to reasonable levels. The switches themselves
carry an interrupting rating similar to those for three-pole interrupter
switches but not as high as that for power circuit breakers. Interrupting capability
for short circuits is almost always handled by current-limiting fuses,
switch has no interrupting or load-carrying capability