I. High-efficiency motor
High-efficiency motors achieve their efficiency by taking measures in design, materials, and processes, such as using reasonable stator and rotor slot numbers, fan parameters, and sinusoidal windings, to reduce losses and improve efficiency by 2%–8%, with an average increase of 4%. In 2002, China's total motor capacity was approximately 400 GW, of which nearly 80% were small and medium-sized motors, consuming 660 TWh annually. The average efficiency of small and medium-sized motors was 87%, while the international advanced level was 92%. The energy-saving potential of small and medium-sized motors in China was approximately 12 TWh.
Driven by energy conservation and environmental protection, high-efficiency electric motors are a current international trend, with the United States, Canada, and Europe successively enacting relevant regulations. Europe's CEMEP standard, based on motor operating time, classifies efficiency into three levels: eff1 (highest), eff2, and eff3 (lowest), implemented in stages between 2003 and 2006. The newly released IEC 60034-30 standard classifies motor efficiency into four levels: IE1 (corresponding to eff2), IE2 (corresponding to eff1), IE3, and IE4 (highest). my country has committed to implementing IE2 and higher standards from July 1, 2011.
With my country's accession to the WTO, the competitive pressure and challenges facing my country's motor industry in the international market have intensified. From both international and domestic development trends, promoting high-efficiency Chinese motors is essential. This is a requirement for product development, enabling Chinese motor products to keep pace with international trends, and also beneficial for advancing industry technology and facilitating product exports. Statistics show that in 2002, motors accounted for over 60% of my country's total electricity consumption, with small three-phase asynchronous motors consuming approximately 35%, making them major electricity consumers. Therefore, developing high-efficiency Chinese motors is a crucial measure to improve energy efficiency, meets my country's development needs, and is therefore essential.
Currently, industrial energy consumption accounts for approximately 70% of my country's total energy consumption, with motor energy consumption accounting for about 60% to 70% of industrial energy consumption. Including non-industrial motor energy consumption, motor energy consumption actually accounts for over 50% of total energy consumption. However, the application rate of high-efficiency energy-saving motors is currently low. According to a sample survey of 198 motors from key domestic enterprises conducted by the National Small and Medium-sized Motor Quality Supervision and Inspection Center, only 8% of these motors met or exceeded the high-efficiency energy-saving standard (Level 2). This results in a significant waste of social resources.
Some organizations have calculated that if the efficiency of all electric motors were increased by 5%, an annual electricity saving of 76.5 billion kilowatt-hours could be achieved, a figure close to the total power generation of the Three Gorges Dam in 2008. Therefore, the energy-saving motor industry has significant growth potential and strong demand. In terms of policy, the National Standardization Management Committee issued the mandatory standard GB 18613-2012, "Minimum Allowable Values of Energy Efficiency and Energy Efficiency Grades for Small and Medium-Sized Three-Phase Asynchronous Motors," in 2012.
II. Characteristics of High-Efficiency Motors
(1) High efficiency: IE2 is on average 3% more efficient than IE1, and IE3 is on average nearly 5% more efficient than IE1.
(2) More high-quality materials are required. The cost of an IE2 motor is 25% to 30% higher than that of an IE1 motor, and the cost of an IE3 motor is about 40% to 60% higher than that of an IE1 motor.
(3) Due to the lower operating temperature, the motor has a longer lifespan and can reduce maintenance costs.
(4) The starting current is relatively large under typical design conditions.
(5) The rotor inertia is large.
(6) The speed is relatively high and the slip is relatively small under rated load.
III. Energy-saving measures for high-efficiency motors
Measures to improve the efficiency of electric motors. Energy saving in electric motors is a systematic project involving the entire life cycle of the motor, from its design and manufacturing to its selection, operation, adjustment, maintenance, and disposal. The effectiveness of energy-saving measures must be considered throughout the entire life cycle of the motor. Domestically and internationally, the main considerations for improving motor efficiency are as follows.
The design of energy-saving motors refers to the use of modern design methods such as optimization design technology, new material technology, control technology, integration technology, and testing technology to reduce the power loss of motors, improve their efficiency, and design high-efficiency motors.
While converting electrical energy into mechanical energy, electric motors also lose some energy. Typical AC motor losses can be divided into three parts: fixed losses, variable losses, and stray losses. Variable losses vary with the load and include stator resistance losses (copper losses), rotor resistance losses, and brush resistance losses. Fixed losses are independent of the load and include core losses and mechanical losses. Core losses consist of hysteresis losses and eddy current losses, which are proportional to the square of the voltage, with hysteresis losses also inversely proportional to the frequency. Other stray losses include mechanical losses and other losses, such as bearing friction losses and wind resistance losses caused by the rotation of the fan and rotor.
