The safe operation of electric motors plays a crucial role in ensuring the normal operation of power systems and the quality of power. Furthermore, electric motors are themselves very expensive electrical components. Therefore, they should be equipped with sophisticated relay protection devices to withstand various faults and abnormal operating conditions. Let's learn some basic knowledge about electric motors!
What is an electric motor?
An electric motor is a component that converts electrical energy from a battery into mechanical energy to drive the wheels of an electric vehicle to rotate.
How can we distinguish between high-speed and low-speed motors based on their type?
A brushed geared hub motor and a brushless geared hub motor are both high-speed motors.
B. Brushed gearless hub motors and brushless gearless hub motors are low-speed motors.
How is the power of an electric motor defined?
The power of an electric motor refers to the ratio of the mechanical energy output by the motor to the electrical energy supplied by the power source.
Why choose the motor's power? What is the significance of choosing the motor's power?
Choosing the rated power of a motor is a crucial and complex issue. Under load, if the motor's rated power is too high, it will frequently operate under light load, failing to fully utilize its capacity – a case of "overpowered motor pulling a small cart." This also leads to low efficiency, poor performance, and increased operating costs. Conversely, if the rated power is too low, it's like "underpowered motor pulling a large cart," causing the motor current to exceed its rated current. This increases internal losses, resulting in lower efficiency, but more importantly, it shortens the motor's lifespan. Even minor overloads can significantly reduce lifespan; severe overloads can damage the insulation material or even burn it out. Of course, an underpowered motor may not be able to drive the load at all, causing it to overheat and be damaged due to prolonged starting. Therefore, the motor's rated power should be strictly selected based on the electric vehicle's operating conditions.
How to identify whether a motor is good or bad? What are the key parameters to look at?
The main factors to consider are the magnitude of the no-load current and the riding current, their comparison with normal values, the efficiency and torque of the motor, and the noise, vibration, and heat generation of the motor. The best method is to use a dynamometer to test the efficiency curve.
What are the differences between 180W and 250W motors? What are the requirements for the controller?
The 250W riding current is large, which places high demands on the power margin and reliability of the controller.
Why does the riding current of an electric vehicle vary depending on the motor's rating under standard conditions?
As is well known, under standard conditions, with a rated load of 160W, the riding current of a 250W DC motor is approximately 4-5A, while the riding current of a 350W DC motor is slightly higher. For example, if the battery voltage is 48V, and both 250W and 350W motors have a rated efficiency of 80%, then the rated operating current of the 250W motor is approximately 6.5A, while the rated operating current of the 350W motor is approximately 9A. Generally, the efficiency of a motor decreases as the operating current deviates from the rated operating current. Under a 4-5A load, with a 250W motor efficiency of 70% and a 350W motor efficiency of 60%, under a 5A load, the output power of the 250W motor is 48V * 5A * 70% = 168W, and the output power of the 350W motor is 48V * 5A * 60% = 144W.
In order for a 350W motor to achieve an output power of 168W (approximately the rated load) to meet the riding requirements, the power supply must be increased to raise the efficiency point.
