Generally, when selecting a fuse, consider its fusing current. For example, a 30-amp fuse means that its fusing current is 30 amps, that is, when the current in the circuit reaches 30 amps, the fuse will blow. But because the current will increase with the increase of load power. Therefore, it will also reflect its power indirectly. If estimated according to the 380V voltage squirrel cage motor, the rated current of a 50KW motor is about 50A, and the rated starting current is 50×6=300A. The calculation formula for selecting the fuse is Inf=le/ (1.8~2.5)=300/2=150A.

The fusing current of the fuse must be between the rated current and the maximum current of the device, so that the normal operation of the device can be ensured. When it is close to the maximum current, the rated current is the current of the electrical appliance working under the rated voltage. It refers to the maximum current allowed for a long time when the heating does not exceed the long-term heating permission temperature under the reference ambient temperature and rated voltage working conditions. . The maximum current refers to a limit value of the current that it can withstand without affecting the safety of the equipment. Usually it can only appear for a short time, otherwise it will cause damage to the equipment.

The maximum operating current of the motor is the operating current that the motor can operate for a long time, usually up to 1.2 times the rated current, and improper calculation of the design power will cause the motor to be selected too small, and the motor can keep working when the rated power is exceeded , The working current at this time is the maximum working current.