How to select reasonable rated current of fuse

　　Since all kinds of electrical equipment have certain overload capacity, it is allowed to run for a long time under certain conditions, and when the load exceeds the allowable value, it is required to fuse the protective melt in a certain time. There are also some equipment starting current is very large, but starting time is very short, so the protection characteristics of these equipment need to adapt to the needs of the operation of the equipment, the fuse is required to start when the motor is not fused, in the short-circuit current under the action and more than the allowable overload current, can be reliable fuse, play a protective role. The melt rated current selection is on the high side, the load can not be timely fused when short-circuit or long-term overload; if the selection is too small, it may be fused under the action of normal load current, affecting normal operation, in order to ensure the normal operation of the equipment, the rated current of melt must be selected reasonably according to the nature of load.
　　1. Lighting Circuit, melt rated current ≥ the sum of the working current of all lighting appliances on the protected circuit.
　　2、Motor:
　　①Single Direct Start Motor, melt rated current = 1.5 ~ 2.5 motor rated current.
　　2 Multiple Direct Start Motors, total protective melt rated current = 1.5 ~ 2.5 sum of motor current.
　　 3 step-down starting motor, melt rated current = 1.5 ~ 2 motor rated current.
　　4 Wound Motor, melt rated current = 1.2 ~ 1.5 motor rated current. 3. Distribution Transformer low-voltage side, melt rated current = 1.0 ~ 1.5 transformer low-voltage side rated current.
　　4. shunt capacitor banks, rated current of melt = 1.43 ~ 1.55 rated current of capacitor banks.
　　Welding machine, melt rated current = 1.5 ~ 2.5 load current.
　　 6. Electronic rectifier, melt rated current ≥1.57.