Non-fused switch disconnectors are a safety device designed to power down or isolate a part of a circuit while it is being serviced or maintained. Unlike fused switch disconnectors, they do not use a fuse to break the circuit, instead using either a rotary or knife-blade disconnect. Rotary switches break the circuit by rotation of a lever, while knife-blade switches use a hinge to lift a lever off its slot.
Non-fused switch disconnectors are used to isolate circuit breakers, transmission lines and transformers as part of their maintenance process. They are a safety measure and are not intended for use as a regular part of the circuit.
Non-fused switch disconnectors vary in the method of disconnecting that they use, whether rotary or knife-blade. Beyond that, they have differing power, voltage and switch ratings, as well as different maximum current capabilities, which will determine which non-fused switch disconnector you choose.