General selection of electric motors

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The last edit to this post was made by A pot of fragrant tea on 2012-8-30 at 09:43. When selecting a motor, it is first necessary to determine the torque at which the motor will operate, as well as the speed required of the motor at that torque level (i.e., the rated speed). Based on this, it is possible to determine what size electrical performance is required to meet this requirement. The rated speed and rated torque of the motor determine its output power. For two motors of exactly the same size, their output power differs due to different rotational speeds and thus different torques. Motors with high torque and high speed have greater output power; naturally, the current also increases. The calculation method for output power is as follows: P2 = 1.028×10^10 × T × N, with the unit being watts (W). Here, T represents the load torque, measured in grams per centimeter (g.cm), and N represents the load rotation speed, measured in revolutions per minute (rpm). For a given motor, when the torque remains constant, the motor’s rotation speed is proportional to the voltage. In other words: the higher the voltage, the higher the rotational speed. For example, a 12V motor has a load speed of 5000 rpm at its rated torque; when the voltage is increased to 24V, the load speed is approximately 10000 rpm. For the same motor, the load speed of a YB explosion-proof motor is inversely proportional to the load torque. In other words, as the load torque increases, the motor speed will decrease. For example, if a motor has a speed of 5000 rpm at a load torque of 200 g.cm, then when the load torque exceeds 200 g.cm, the motor’s speed will be lower than 5000 rpm ； And when the load torque is less than 200 g.cm, the motor speed will be higher than 5000 rpm. Generally, the load torque applied to the motor should be the same as the rated torque specified for the motor. Because, when operating at the rated torque, the motor is near its highest efficiency point. When the load torque exceeds the rated torque, the motor operates under overload conditions, which will affect its heating and service life. The torque of a motor is usually expressed in g.cm (grams per centimeter). The conversion factors to other units of torque are as follows: 1 g.cm = 0.098 mNm = 0.014 oz-in; 1 mNm = 10.2 g.cm = 0.142 oz-in; 1 oz-in = 7.056 mNm = 72.0 g.cm. The conversion factors for length units are: 1 mm = 0.039 in; 1 in = 25.4 mm. The conversion factor for weight units is: 1 g = 0.035 oz; 1 oz = 28.35 g