What is the Outer Rotor Motor?

In the outer rotor bldc motor, the rotor is placed on the outside of the stator, hence the name "outer rotor". Its structure and working principle are very simple. It is composed of rotating part (rotor), static part (stator), end cover and bearing. When the alternating current passes through the stator winding, a rotating magnetic field is generated in the stator winding. The permanent magnet in the rotor induces the rotational speed of the stator rotating magnetic field, and then begins to rotate. In rotation, the air gap between the rotor and the stator produces an electromagnetic induction effect, which produces an electric torque that causes the rotor to continuously rotate continuously. It is not only simple in structure, but also has obvious advantages. The characteristics of small starting current, large torque and good stability make it widely used in home appliances, electric tools, automobiles and other fields. In addition, it also has a small shape, easy to install, smooth operation, low failure rate characteristics. In the industrial automation and other fields, the external rotor motor is one of the indispensable power.

Because of its compact structure, high speed, high efficiency, low noise characteristics, it is widely used in various fields.automotive filed, Used as components such as car electric turbochargers, car brakes and electric motors, Its high efficiency and high speed to ensure the performance and reliability of the automobile power system; Aerospace field, Used in aerospace electric engines, hydraulic pumps, air conditioning and other fields, Its brushless structure and high performance to ensure the stability and reliability of the system; Industrial production field, Is used as various industrial production equipment, Such as CNC machine tool, laser cutting machine, injection molding machine, Its high speed and fast response characteristics improve the production efficiency and quality stability; Smart home sector and home appliances sector, Being used in smart homes and home appliances, Such as intelligent vacuum cleaner, intelligent boiler, intelligent dehumidifier, etc., Its high efficiency and low noise characteristics to ensure the product performance and user experience; Medical device field, Are being used as various medical devices, Such as surgical instruments, ventilators, centrifuges, Its high reliability and high efficiency ensure the life safety and medical effect of patients.

KV Value

The KV value of the motor is the speed constant of each voltage unit, and it is usually used to describe the characteristics of the brushless motor. The higher the KV value, the faster the motor turns. For example, a motor with a KV value of 3,000 can reach 36,000 rpm at a voltage of 12V. The KV value is an important parameter that can help us to select motors suitable for different needs. For example, for high acceleration and response applications such as aircraft, motors with high KV values can be selected. For uses requiring long operation and high durability requirements, the motor with low KV value can be selected. It is worth noting that the higher the KV value is not the better. When the motor consumes electricity, the higher the KV, the greater the current of the motor, resulting in shorter battery life. Therefore, we need to make choices based on the specific situation. A brush DC motor is according to the rated working voltage to mark the rated speed, the brushless motor introduced the concept of KV value, so that the user can intuitively know the specific speed of the brushless motor at the specific working voltage. Actual speed =KV value * working voltage, which is the practical significance of KV, which is the speed per minute at 1V working voltage. The speed of the brushless DC motor is directly proportional to the voltage, and the speed of the motor will rise linearly with the voltage rise.

Rated Voltage

That is, the power supply voltage where the motor can work normally. In practical applications, the supply voltage is usually determined according to the characteristics of the selected brushless motor and the required workload. Generally speaking, the rated voltage of brushless motor is usually between 6 V and 36 V, with different types of electrical opportunities. In order to ensure the normal operation of the brushless motor, it is necessary to pay attention to the following points: select the appropriate power supply voltage, not exceeding the rated voltage range of the motor; ensure the stability of the power supply voltage, avoid the influence of excessive or small voltage fluctuations in the motor, and try to ensure the life and performance of the motor.

Torque

It refers to the amount of the moment it can produce, that is, the amount of force it generates when running. The torque size depends on the magnetic field strength and the current size of the motor, so the torque of the brushless motor can be controlled by adjusting the current size of the motor. The driving torque generated by the rotor in the motor that can be used to drive the mechanical load can understand the power of the motor.

Speed

The rotational speed per minute of the motor is generally expressed by the RPM. Do not need a traditional brush to transfer electricity to the rotor, but use electronic components to complete electromagnetic induction. As a result, the brushless motor will have higher speeds and the rotor is more stable, thus improving the efficiency and reliability. The brushless motors also have lower noise and less electromagnetic interference than conventional brushed motors. The speed is affected by a variety of factors, such as voltage, current, motor quality, quality of magnet and so on. In the normal operating range, the speed of the brushless motor is usually between thousands to a hundred thousand revolutions. For some high-end brushless motors, they can even exceed hundreds of thousands of RPM, providing strong support for some high-speed applications.

Maximum Current

The maximum current that the motor can withstand at the specified voltage. Because the brushless motor has the characteristics of high efficiency and high power, its maximum current is generally large, usually about 10A~50A, some high power brushless motor can reach more than 100A. However, it should be noted that the maximum current is only the limit value that the motor can withstand, not the value that must be reached. In actual use, reasonable current control should be carried out according to the specific motor type and use conditions to ensure the normal operation and long-term use of the motor. In addition, attention should be paid to the selection of batteries and other supporting equipment to ensure that they can adapt to the selected motor.

Maximum Power

The maximum power that the motor can withstand and work safely is power = voltage * current, determined by the internal components and design of the motor. Usually, the maximum power of a brushless motor can reach several kilowatts or even more.

Brushless motor power and efficiency

We can simply understand that the motor output power = speed * torque, under the same power, the torque and speed is a relationship between the other, that is, the higher the speed of the same motor, the lower the torque, on the contrary, it is still. Power refers to the energy output by a brushless motor, which is usually expressed in physics by the work done per unit of time. Generally speaking, the greater the power of a brushless motor is, the stronger its output capacity is, and the greater it can bear the workload in actual use. Efficiency refers to the ratio of the energy consumed by the brushless motor to the output, that is, the energy conversion efficiency of the motor. Brushless motor has the advantages of high efficiency, which can convert most of the energy into mechanical energy, resulting in higher energy efficiency, less energy loss.

About the magnets for the brushless motor

It refers to a permanent magnet used to produce a magnetic field. Its main function is to interact with the coils in the brushless motor to realize power transfer and conversion. Compared with the traditional brushed motor, the brushless motor uses the permanent magnet as the magnetic field source, which makes the movement of the brushless motor more stable, and does not need to replace the brush frequently, which reduces the maintenance cost and maintenance complexity. Brushless motor magnet usually uses high-performance rare earth magnetic materials, such as NdFeB magnet, because of its high magnetic energy product, high temperature stability, corrosion resistance and other advantages, NdFeB magnet is 3 times that of the common black ferrite magnet in our life, and the price is more than 10 times that of ferrite magnet. Brushless motor ultimately belongs to the permanent magnet motor, and the power, characteristics and other characteristics of the permanent magnet motor depend on the magnet.

The above are some professional knowledges on outer rotor brushless dc motor by VSD Motors. For more relevant information, please contact us.