# Mechanical characteristic curve of multistage gear cutting motor in shearer cutting section

The cutting motor of shearer is squirrel cage three-phase asynchronous motor. The mechanical characteristics of cutting motor refer to the relationship between output torque and motor speed

Where Tmax and SM are the maximum torque and critical slip rate of the motor respectively, which can be obtained from the data found in the motor product catalog, so the formula is called practical expression; s is slip rate, which means the difference percentage between motor running speed and synchronous speed, s = (ns-n) / NS, where ns is synchronous speed and N is motor running speed. Now we introduce the solution method of Tmax and SM as follows:

Where, KT is the overload multiple of the motor, and the overload multiple of the general asynchronous motor is 1.8 ~ 3.0, which reflects the limit of the motor not stopping due to short-term overload; TN is the rated torque of the motor, which is a required parameter of each motor; SN is the rated slip of the asynchronous motor, which can be obtained from the synchronous speed and rated speed according to SN = (NS NN) / NS, where NN is the rated speed.

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