Motor torque, in simple terms, refers to the magnitude of the rotational force. However, the torque of the motor is proportional to the strength of the rotating magnetic field and the current in the rotor bars, and is proportional to the square of the power supply voltage. Therefore, the torque is determined by the factors of current and voltage. The "torque" of the motor is in N·m (Nm）Calculation formulaIt is T=9550*P/n. P is the rated (output) of the motorPower Unityeskilowatt(KW)DenominatoryesRated speedThe unit of n is revolutions per minute (r/min)P and n can be obtained from the motorNameplateBecause P and n are both motorRating, so T is the rated torque of the motor. The output torque of the motor in normal operation varies with the load, but in general, the output torque of the motor refers to the rated output torque M at rated power and rated speed, M=9550N/n. The motor power is constant, the speed is constant, and the torque is constant. The motor output torque is constant under rated conditions, but the starting torque is a multiple of the rated torque. For general three-phase asynchronous motors, such as Y and Y2 series motors, the relevant data can be found in the motor sample, which represents the starting ability of the motor under load. For example, the starting multiple of special high slip motors is much higher. For example, the winding motor: such as the YR series, it is even higher. You can check the relevant samples. Rated torque: The electromagnetic torque generated on the motor shaft under rated voltage and rated load is called the rated torque of the motor. Starting torque: When voltage is applied to an asynchronous motor in a stopped state, the torque generated by the asynchronous motor is called starting torque. Starting torque characterizes the starting ability of the motor, which is related to the starting method (such as star-delta starting, variable frequency speed control starting, etc.). Direct starting squirrel cage type is generally 0.8 to 2.2 times the rated torque. Usually the starting torque is more than 125% of the rated torque. The corresponding current is called starting current, which is usually about 6 times the rated current. For DC motors, the starting torque is very large, so the starting current is also very large, so they cannot be started directly. Of course, this is for large DC motors, and small DC motors including permanent magnets are exceptions. For AC motors, the torque is not very large, so the current is not very large, and they can be started directly. Of course, AC motors have a small starting torque, so they cannot be started with load.Maximum torque: The point where the motor torque enters the unstable zone from the stable zone. In other words, if the load torque is greater than the maximum torque of the motor, the motor's output torque will decrease and enter a stalled state. Stall torque: After entering the stall state, the speed is zero, and the torque that the motor can output is the stall torque. Static torque: The torque when the stator locks the rotor when the motor is powered but not rotating. The maximum torque multiple and the stall torque multiple are indeed two important performance indicators to measure the motor performance, but the bigger the better is not necessarily true. The larger the maximum torque multiple, the more capable the motor is of overloading, but at the same time, it is also a very important assessment of the size and materials of the motor. It is good to have a larger stall torque multiple, especially for large motors, which generally have a larger moment of inertia. If the stall torque multiple is larger, the motor will start faster and rotate more freely. However, the larger the stall torque multiple, the better. The larger the torque multiple is, the greater the starting current of the motor will be, and the greater the impact on the power grid will be. Therefore, when choosing a motor, you should choose a suitable value according to the actual working conditions and keep a certain margin. In general, the stall torque multiple is 1.8-2.2. The maximum torque multiple is 2.0-2.8. The starting torque is a torque that is 1.7 to 2.2 times greater than the rated torque generated at startup. The starting torque can overcome the static friction of the rotor and the resistance generated by the load driven by the motor.The torque of the motor is divided into starting torque, maximum torque and rated torque.
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