The application range of electric motor

Among various types of electric motors, the most widely used is the AC asynchronous motor (also known as the induction motor). It is convenient to operate, reliable in performance, cost-effective, and structurally robust, but it has a relatively low power factor and difficult speed regulation. For high-capacity, low-speed power applications, synchronous motors (see synchronous motor) are commonly employed. Synchronous motors not only boast a high power factor but also maintain a speed independent of load magnitude, determined solely by the grid frequency. They operate with greater stability. In scenarios requiring wide-range speed control, DC motors are frequently utilized. However, they feature commutators, complex structures, high costs, and maintenance challenges, making them unsuitable for harsh environments. Since the 1970s, advancements in power electronics have matured AC motor speed regulation technology, driving down equipment costs and enabling its widespread adoption. The rated power of a motor refers to the maximum mechanical output it can sustain under specified duty cycles (continuous, short-time, or intermittent periodic operation) without overheating, and operational parameters must adhere to nameplate specifications. During operation, it is essential to match the load characteristics with the motor's performance to prevent runaway or stalling. Electric motors span an extensive power range, from milliwatts to megawatts. Their operation and control are highly convenient, featuring self-starting, acceleration, braking, reversal, and holding capabilities. Typically, motor output power varies with rotational speed during speed regulation.

High-efficiency motors can replace the JO2 series motors with Y series AC asynchronous motors without being significantly constrained by motor types. Therefore, all applications involving AC asynchronous motors can be substituted with Y series motors. The market potential of the Yx series motors is limited by their capacity. In principle, AC asynchronous motors below 90kW can be replaced by high-efficiency Yx series motors. The installed capacity of AC asynchronous motors below 90kW accounts for approximately 30% of the total AC asynchronous motor capacity.

Over the past decade, the Chinese government has been committed to promoting motor speed regulation technology, which has been adopted to varying degrees across various industries. According to sample surveys conducted by sectors such as petroleum, power, building materials, steel, nonferrous metals, coal, chemicals, papermaking, and textiles, the petroleum, building materials, and chemical industries have achieved relatively better applications of motor speed regulation. Among the 400 million kW of motor loads, approximately 50% experience load fluctuations, with 30% of these fluctuations being addressable through motor speed regulation. Therefore, considering market capacity alone, there is a potential market for about 60 million kW of speed-regulated motors. China's total installed capacity of various motors has exceeded 400 million kW, with asynchronous motors accounting for about 90%, small and medium-sized motors making up approximately 80%, and motors driving fans, pumps, compressors, and similar machinery totaling around 130 million kW. Small and medium-sized motors now encompass over 152 series, 842 types, and more than 4,000 specifications. In recent years, relevant departments such as the machinery industry have vigorously promoted motor energy conservation efforts, organizing research institutes and enterprises to design and develop various energy-saving motors. Regulatory measures have been issued to phase out 63 high-energy-consuming motor models and promote 24 energy-saving motor models, achieving certain results. These energy-saving products are primarily divided into two categories: one is high-efficiency motors designed to improve motor efficiency, and the other is speed-regulated motors.

The brushless DC motor consists of the motor body and the drive unit, making it a typical electromechanical integrated product. The stator windings of the motor are mostly connected in a three-phase symmetrical star configuration, which is very similar to that of a three-phase asynchronous motor. The rotor of the motor is equipped with permanently magnetized magnets. To detect the polarity of the motor rotor, a position sensor is installed inside the motor. The drive unit is composed of power electronic devices and integrated circuits, among others, and its functions include: receiving start, stop, and brake signals from the motor to control its operation; accepting position sensor signals and forward/reverse signals to regulate the switching of the power tubes in the inverter bridge, thereby generating continuous torque; receiving speed command and feedback signals to control and adjust the rotational speed; and providing protection and display functions, among others.

Since brushless DC motors operate in self-controlled mode, they do not require additional starting windings on the rotor like synchronous motors under variable frequency speed regulation, nor do they experience oscillations or stepping during load changes. For medium and small-capacity brushless DC motors, permanent magnets are typically made from high-magnetic-energy rare-earth neodymium iron boron (Nd-Fe-B) materials. As a result, rare-earth permanent magnet brushless motors are one frame size smaller than three-phase asynchronous motors of the same capacity. Over the past three decades, research on variable frequency speed regulation for asynchronous motors has essentially focused on finding ways to control their torque. Rare-earth permanent magnet brushless DC motors will undoubtedly demonstrate advantages in speed regulation due to their wide speed range, compact size, high efficiency, and minimal steady-state speed error. Brushless DC motors, inheriting the characteristics of brushed DC motors while also functioning as frequency conversion devices, are also known as DC frequency converters, with the internationally recognized term being BLDC. In terms of operational efficiency, low-speed torque, and speed accuracy, brushless DC motors outperform any frequency converter with control technology, making them worthy of industry attention. The product has already been manufactured with capacities exceeding 55kW and can be designed up to 400kW, addressing the industrial needs for energy savings and high-performance drive solutions.