In electrical engineering, motor speed and torque are very important parameters. In practical applications, the calculation formulas for motor speed and torque are also used very frequently. This article introduces torque calculation formula and speed calculation formula in detail.According to the definition of torque in "GB/T 2900.61-2008 Electrical Terminology Physics and Chemistry" : Torque refers to the sum of the moments of a group of forces whose resultant force is zero .Torque is the basic load form of the transmission shafts of various working machinery and is closely related to factors such as the working capacity , energy consumption, efficiency, operating life and safety performance of the power machinery. In electrical machinery, torque, torque and torque are the same. Under the condition of fixed power, the torque is inversely proportional to the engine speed. The faster the speed, the smaller the torque, and vice versa. In motors, it refers to the driving "torque" generated by the rotor winding in the motor that can be used to drive the mechanical load. The so-called "moment" refers to the product of the force and the distance perpendicular to the direction of the force from the fulcrum. The international unit is Newton-meter Nm. Definition of speed "GB/T 2900.36-2003 Electrical Terminology Electric Traction" defines speed: the speed at which the motor rotates. Represented by the symbol "n"; its international standard unit is rps (revolution/second) or rpm (revolution/minute). When the unit is r/S, it is numerically equivalent to frequency, that is, n=f=1/T, T is the period of circular motion. The linear velocity corresponding to a certain point on the circle is: v=2π*R*n, where R is the rotation radius corresponding to the point.
2. Motor speed and torque calculation formulas
Motor speed formula: n=60f/P n=speed, f=power frequency, P=number of magnetic pole pairs Motor torque formula: T=9550P/n T is torque, unit is N·m P is output power, unit is KW n is motor speed, unit is r/min For the specific derivation process, please refer to: Derivation and memory method of calculation formulas for torque and power The meaning of the two parameters: 1kg=9.8N: The attraction force of a 1kg object on the earth is 9.8 Newtons. 9.8N·m: The force acting vertically at the thrust point 1 meter away from the center of the grinding disc is 9.8N.
3. How to reasonably select a motor through motor power and torque calculation formulas
We know that whether the motor is too large or too small, abnormalities will occur. If the power of the motor is too small, a "small horse pulls a big cart" phenomenon will occur, causing the motor to be overloaded for a long time, causing its insulation to be damaged due to heat, or even the motor to be burned. If the power of the motor is too large, the "big horse and small cart" phenomenon will occur. Its output mechanical power cannot be fully utilized, and the power factor and efficiency are not high. This is not only detrimental to users and the power grid, but also causes a waste of electrical energy. Therefore, the selection of motor power should be based on the power required by the production machinery, and try to make the motor run under the rated load. To correctly select the power of the motor, the following calculations or comparisons must be made. For, calculate the power required by the motor according to the following formula: P=F*V/1000 P=calculated power KW, F=required pulling force N, working machine linear speed M/S For constant load continuous operation, the required motor power can be calculated as follows: P=P/n1n2 In the formula, n1 is the efficiency of the production machinery; n2 is the efficiency of the electric motor, that is, the transmission efficiency. When selecting a motor, the rated power of the selected motor should be equal to or slightly greater than the calculated power.
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