Why are there fuses in Model B Static Transfer Switches and not others?
Our static switches are manufactured to be rugged and our larger units don’t have internal protective fuses and or circuit breakers. The devices are purposely overrated to cope with external short circuits without failure or loss of output. For safety reasons there needs to be some protection between the source and the load. This protection is graded to limit the fault currents to below the specified fault rating (kA rating) such that the protective device opens the circuit within 10 milliseconds, (1/2 a cycle). Most circuit breakers will enable settings to be selected to easily achieve this. kA Rating of devices vary from 2kA in small Point of Distribution Rack Mounted Static Transfer Switches to 9kA, 15kA, 30kA, 36kA, 40kA and 50kA and beyond. This additional kA capacity is gained by over sizing the semiconductors used to undertake the switching process. Obviously the higher the kA rating the larger the device and the greater the cost. If you choose to low a kA rating or do not have
