Rated Speed Of The Motor
May 12, 2025
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The rated speed of a motor refers to the speed at rated operating mode.
Xi'an Simo motors and the working machines driven by them have their own rated speeds. When choosing the speed of the motor, it should be noted that the speed should not be too low, because the lower the rated speed of the motor, the more stages it has, the larger the volume, and the higher the price; at the same time, the speed of the motor should not be too high, because this will make the transmission mechanism too complicated and difficult to maintain.
In addition, when the power is constant, the motor torque is inversely proportional to the speed.
Therefore, those with low requirements for starting and braking can make a comprehensive comparison of several different rated speeds from the aspects of initial equipment investment, floor space and maintenance costs, and finally determine the rated speed; while those with frequent starting, braking and reversing, but the duration of the transition process has little effect on productivity, in addition to considering the initial investment, mainly select the speed ratio and motor rated speed based on the condition of minimizing the loss during the transition process. For example, the hoist motor needs to frequently rotate forward and reverse and has a large torque, so the speed is very low, the motor is bulky and expensive.
When the motor speed is high, the critical rated speed of the motor must also be considered. The motor rotor will vibrate during operation, and the amplitude of the rotor increases with the speed. At a certain speed, the amplitude reaches the maximum value (which is usually called resonance). After exceeding this speed, the amplitude gradually decreases with the speed increase and stabilizes within a certain range. The speed at which the rotor amplitude is the largest is called the critical speed of the rotor.
This speed is equal to the natural frequency of the rotor. When the rated speed continues to increase and approaches 2 times the natural frequency, the amplitude will increase again. When the speed is equal to 2 times the natural frequency, it is called the second-order critical speed. By analogy, there are third-order and fourth-order critical speeds. If the rotor runs at the critical speed, it will vibrate violently, and the curvature of the shaft will increase significantly. Long-term operation will also cause serious bending and deformation of the shaft, or even breakage.
The first-order critical speed of Xi'an Simo motor is generally above 1500 rpm, so the influence of critical speed is generally not considered for conventional low-speed motors. On the contrary, for 2-pole high-speed motors, the rated speed is close to 3000 rpm, and this influence needs to be considered, and the motor should be avoided from being used in the critical speed range for a long time.
Generally speaking, the motor can be roughly determined by providing the driven load type, rated power, rated voltage, and rated speed of the motor. However, if you want to optimize the load requirements, these basic parameters are far from enough. Other parameters that need to be provided include: frequency, working system, overload requirements, insulation level, protection level, moment of inertia, load resistance torque curve, installation method, ambient temperature, altitude, outdoor requirements, etc., which should be provided according to the specific situation.
CHOOSE SIMO, CHOOSE QUALITY!
