The maximum torque is one of the most important power parameters of the motor, also called the stall torque. Under the rated voltage and frequency, gradually increase the load until the motor speed drops suddenly, the shaft end torque of the motor corresponding to the maximum load is the maximum torque, which is the limit capacity of the motor. When loading a load that exceeds the limit capacity of the motor, the balance between the output torque of the motor and the applied torque will be broken, so it is described in Chinese as stall torque or limit torque.

Different operating conditions have different requirements for the maximum torque of the motor. In general, the maximum torque is more than twice the rated torque. The minimum value is 1.6 to 2.5 times the rated torque, and it can also be designed to be 2.8 to 3.0 times when there are special requirements.

The maximum torque is an important technical index to measure the short-term overload capacity of the motor. The greater the maximum torque, the stronger the motor's ability to withstand mechanical loads.

The motor may be temporarily overloaded during load operation. When the maximum torque of the motor is less than the resistance torque of the load, the motor will stop, and the windings of the motor will burn out due to the increase in current. For the working condition where the actual operating load is less than the rated load, the requirement for the maximum torque is relatively small, otherwise, it must be designed and controlled according to the demand.

During the test, the direction of rotation of the load motor and the motor under test should be the same. Adjust the power supply voltage of the load motor, gradually increase the load of the motor under test until the dynamometer current reaches the maximum value, read this value, the terminal voltage of the motor under test, and the speed of the unit. During the test, the motor under test should be prevented from overheating, and the load should not be adjusted too fast to avoid impact.

The maximum torque of an asynchronous motor is the maximum electromagnetic torque that the motor can produce at rated voltage and rated frequency. The size of the torque reflects the overload capacity of the motor. The correct measurement of this torque not only brings convenience to the user to select the motor, but also provides an important basis for ensuring the reliable operation of the motor.

When the voltage is applied to the AC asynchronous motor in the stopped state, the torque generated by the AC asynchronous motor is called the starting torque. The starting torque is proportional to the square of the voltage, related to the leakage reactance of the motor, and increases with the increase of the rotor resistance.

Torque is the basic load form of transmission shafts of various working machines. It is closely related to factors such as working capacity, energy consumption, efficiency, operating life and safety performance of power machinery. The strength design of the working parts of the system and the selection of the prime mover capacity are of great significance.