Discussion on the effect of copper on improving the energy efficiency of motor

Copper has excellent electrical conductivity, which is the reason why copper is widely used in the field of power supply and use. The application of copper in the field of motor is of great significance to improve the energy efficiency of motor. As a successful case of copper in the field of high efficiency motor, cast copper rotor motor has many advantages, such as high efficiency, low material cost, light weight, small volume, long service life and so on. This paper will focus on the role of copper in improving the energy efficiency of motor, the main equipment used for electric energy.

Significance of improving motor energy efficiency

As one of the most important power equipment in production and life, motor is responsible for converting electrical energy into mechanical energy to drive mechanical equipment. According to the statistics of the U.S. Department of energy, the electric power consumption of the U.S. motor accounts for 2 / 3 of the total industrial power consumption, accounting for 1 / 2 of the total power consumption, and the energy transmitted by the motor consumes 20% of the total primary energy. Statistics of the European Union show that the total electricity consumption of the European Union in that year was 1700 billion kwh, of which the electricity consumption of electric motors was 719 billion kwh, accounting for 42% of the total electricity consumption. At the same time, the power consumption of motor accounts for about 60% of the total power consumption of our society.
It is precisely because the proportion of motor in industrial power is so large, improving the energy efficiency of motor is of great significance to promote energy conservation, environmental protection and sustainable development. According to the prediction of relevant EU experts, the power consumption of asynchronous motors in the EU’s industry and tertiary industry will reach 872 billion kwh. If the efficiency of motors with different power can be increased by 1% – 6%, about 3% of electric energy will be saved, which is worth 2.6 billion euro (10 euro / kWh).
Similarly, in the United States, a single percentage point increase in the efficiency of electric motors can save about 20 billion kwh of electricity annually, worth $1.4 billion (7 cents / kWh). In China, in order to implement the scientific concept of development, realize the coordinated and sustainable development of human and environment, it is of great significance to improve the energy efficiency level of motor. The energy-saving project of motor system has been listed in the top ten energy-saving projects implemented during the 11th Five Year Plan period, which fully reflects the importance of motor energy-saving work.

How to effectively improve the energy efficiency of motor

In order to improve the energy efficiency of the motor, it is necessary to reduce the loss of the motor. Taking the most commonly used three-phase AC asynchronous motor as an example, the loss of the motor mainly includes core loss, stator and rotor copper loss, wind friction loss and stray loss. Their proportion in the total loss of the motor and the main influencing factors are as follows:

Loss type	Proportion %	Influence factor
Core loss	15-20%	Permeability of iron core materials: air gap
Wind friction loss	5-15	Fan efficiency: Bearings: Lubricants
Stator winding (copper) loss	30-45	Stator conductor size: heat dissipation factor
Loss of rotor winding (copper or aluminum)	20-25	Rotor cage size: heat dissipation factor
Stray loss	10-15	Manufacturing industry: groove design: air gap

The proportion of motor total loss and the main influencing factors

It can be seen from the table that the copper loss of the stator and rotor accounts for a large part of the total loss of the motor, and copper can play an important role in reducing the loss of the stator and rotor of the motor. For the copper loss of stator winding, pcu1 is mainly the resistance loss of stator winding at operating temperature under full load. The calculation formula of copper loss of stator winding is as follows:

Stator copper loss accounts for a large proportion of motor loss. How to reduce the copper consumption of stator is very important to improve the efficiency of motor. To reduce the copper consumption of the stator is to reduce the resistance R1 and the current I1 of the stator. Because of the stator resistance R1 =ρL /S, to reduce the stator resistance is to shorten the coil length L, increase the cross section s of each coil and reduce the conductor resistivity ρ To achieve.
Because of the extremely low resistivity of copper, most motors use copper wire to make stator windings. For the motor with copper winding, increasing the cross section of copper wire is a key measure to develop high efficiency motor. In recent years, some high-efficiency motors have been developed firstly. Compared with traditional motors, the usage of copper windings has increased by 25-100%.
For the rotor loss, the vast majority of the motor rotor is cast aluminum rotor. If cast copper rotor is used to replace the cast aluminum rotor widely used in squirrel cage three-phase asynchronous motor, the total loss of the motor will be significantly reduced, so as to improve the overall efficiency of the motor. High efficiency and even super efficiency motors can be produced by using cast copper rotors. Under the condition of the same motor size, higher motor energy efficiency level can be achieved. For example, from eEF2 to eff1.
Or, upgrade from EPACT (federal energy efficiency regulation) for ordinary induction motors to NEMA (National Electrical Manufacturers Association) premium ultra efficiency standard. According to the characteristics of the cast copper rotor, redesigning the rotor and stator of the motor can maximize the efficiency and achieve higher or even super premium super efficiency energy efficiency standards.
Source: China Permanent Magnet Manufacturer – www.rizinia.com