Motor technology upgrade direction
By studying the technological evolution of motors over the past 20 years, we have found that there is still a large room for further improvement in motor technology. First look at the thickness of the steel for the movement. For the stator and rotor, it is mainly composed of a thin layer of electromagnetic steel. In 1997, the first generation of Toyota Prius used a 0.35mm steel layer, which was subsequently reduced to 0.3mm, and recently dropped to 0.25mm in 2016. In general, an increase in the number of layers of thin steel can increase the efficiency of the motor and also help control the temperature of the motor.
At present, manufacturing thin steel is a major technical problem in the industry. The main difficulty lies in controlling the rebound in the die casting and the consistency of the steel sheet material. From the current situation, the rotary forging technology will become more and more the mainstream manufacturing method in the industry due to its advantages in cost and production efficiency.
Secondly, in terms of winding density, the amount of winding in the stator as a whole is an important factor determining the power of the motor. The number of windings is determined by the number of turns that the copper wire can wrap around the movement in a limited space. In terms of technology, the use of the inserter is suitable for high-power stator processing and has become a trend in the industry.
In terms of coil type, there are mainly square and round. At present, mainstream manufacturers use circular, but square technology is gradually replacing circular as the industry has a high space utilization rate, while Toyota and Honda are currently Square winding technology has been adopted in batches. Other manufacturers here, Yaskawa Electric has begun to develop electronic winding technology, the purpose is to improve control and efficiency (Mazda has begun trial).
Finally, in terms of the cooling system, the split motor and the inverter are two parts: the motor. Since the magnetic force of the permanent magnet motor is weakened as the motor temperature increases, the efficiency of the cooling system is critical for the high-power operation of the motor.
From the trend of technology evolution, the mainstream cooling technology has evolved from air-cooled and water-cooled to the current stage of oil cooling. The main technical means is to immerse the motor in the oil cooling chamber to achieve the purpose of cooling. Although some experts believe that friction with oil will reduce the efficiency of the motor, but in all aspects, oil cooling is still the most effective cooling mode under current technical conditions.
In terms of inverters, the cooling system is also important for the performance of the inverter. Nissan recently claimed to increase the output power of the motor from 80kw to 110kw in the new 2017 model of the wind, by increasing the inverter cooling system. Some are the same as the previous generation.
This reflects the importance of the inverter cooling system. Although the use of silicon carbide will increase the heat resistance and pressure resistance of the motor, its high cost, the time of its large-scale application may be difficult to come in the short term.
