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Is higher motor speed always better in terms of performance?

When selecting a motor for a given application, it is important to consider how the specific requirements in terms of power, torque, speed, load characteristics, cooling abilities, noise limitations, and other factors relate to each other.

As the core of an electric vehicle, the performance of the motor is of utmost importance, especially as the speed of the motor directly affects the output power and efficiency of the motor.

However, the size of a motor's speed is influenced by multiple factors, including the motor's model, voltage, current, and load. Currently, it is considered a bottleneck technology.

But does a higher motor speed always mean better motor performance? The answer is NO. A good motor's performance is related to the specific application needs and motor design.

Motor speed determining factors:

  1. For synchronous or asynchronous motors, the speed of the motor is related to the frequency of the power source and the number of motor poles. The higher the frequency of the power source and the fewer the number of poles, the higher the speed of the motor. For asynchronous motors, the speed is also related to the current passing through the motor coil. The larger the current, the closer the speed is to the synchronous speed. There is also a class of motors (usually AC-DC motors) whose speed is irrelevant to the frequency of the power source, only related to the size of the current passing through the coil.
  2. Generally speaking, the speed of common motors is several hundred to several thousand revolutions per minute.

Normal motor speed:

2-level motor: 3000 revolutions

4-level motor: 1500 revolutions

6-level motor: 1000 revolutions

8-level motor: 750 revolutions

10-level motor: 600 revolutions

16-level motor: 500 revolutions

  1. The speed of the motor is determined by the structure of the motor and the method of power supply. The speed of a general motor is several hundred to several thousand revolutions per minute.

The performance of the motor is affected by multiple factors, including speed, power, efficiency, and torque. Here are some considerations:

Power density: Higher speeds generally increase the power density of the motor, i.e., the power output per unit volume or weight. This may be beneficial for some applications that require high power output, such as high-speed mechanical or vehicle power systems.

Dynamic response: Higher speeds may help improve the dynamic response capability of the motor, making it faster to respond to load changes or achieve precise motion control. This is important for some applications that require fast response and high precision control.

Efficiency: The efficiency of the motor typically reaches its maximum value within a specific speed range. Within this speed range, the motor can convert the input electrical energy into mechanical energy output at a higher efficiency. However, if the speed exceeds this range, the efficiency of the motor may decrease. Therefore, selecting an appropriate speed to improve the motor's efficiency is important.

Torque output: The torque output of the motor is typically related to the speed. In some applications, such as starting or climbing, a higher torque output may be required while sacrificing some speed. Therefore, for these applications, low-speed high-torque motors may be more suitable.

Axial load and vibration: Higher speeds may increase the axial load and vibration that the motor bears, which may negatively impact the motor's lifespan and reliability. Therefore, it is necessary to consider the specific application requirements and motor design parameters to balance the relationship between speed and load.

In summary, the impact of speed on motor performance is complex, and there is no consistent rule. The best speed depends on the specific application requirements, including the required power, torque, efficiency, and response speed. Therefore, when selecting a motor, it is necessary to comprehensively consider the speed and its relationship with other performance indicators to meet the specific application's requirements.

Additional factors to consider include:

Power requirements: Specific applications may have specific power requirements. In some cases, higher speeds may provide larger power output, thus meeting the application requirements. However, this is not applicable to all situations. Sometimes, lower speeds may be required to provide the necessary power and torque.

Dynamic balance: High-speed rotating motors may require more complex balancing measures to reduce vibration and noise. This may include higher precision bearings, dynamic balancing of rotating parts, etc. Therefore, when running at high speeds, special attention must be paid to the motor's balance performance.

Axial and radial loads: Higher speeds may increase the axial and radial loads that the motor bears. Therefore, when designing and selecting motors, it is necessary to ensure that the motor can withstand these loads to prevent motor damage or premature wear.

Cooling and heat dissipation: Higher speeds generate more heat, requiring a more powerful cooling system to ensure that the motor runs within an acceptable temperature range. Therefore, high-speed motors typically require more efficient cooling and heat dissipation measures.

Noise and vibration: High-speed rotating motors may generate more noise and vibration. For some applications, this may be unacceptable, and noise and vibration control measures, such as soundproof covers and vibration isolation mounts, must be taken.

In summary, the impact of speed on motor performance is a complex issue involving multiple factors. When selecting a motor, it is necessary to comprehensively consider the application requirements, power requirements, torque requirements, balance performance, load requirements, cooling requirements, noise, and vibration control, etc., to find the most suitable speed range for a specific application.

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