Who Decides On The Good Or Bad Of The Motor?

Who decides on the "good or bad" of the motor?

 

In the era of trams, how should the motor be evaluated as good or bad?

Perhaps many people will think that the type of motor determines the quality of the motor.

 

As the two most used motors at present - permanent magnet synchronous motor and AC asynchronous motor, although the outside world has its own views on the two types of motors, in fact, both have their own advantages, and can not rely solely on the type to evaluate the good or bad.

 

Some people also think that the quality of the motor should be related to its performance parameters, such as acceleration, extreme speed and power consumption, no matter what kind of motor, as long as these three parameters are higher, the better the motor.

 

But in fact, extreme speed, acceleration, and power consumption cannot determine the quality of the motor, because after them, there is a core element that limits their upper limit, resulting in the motor unable to make more extreme performance.

 

The core of truly evaluating the quality of the motor is heat dissipation. Whether it is the acceleration ability of the tram, the long-lasting extreme speed performance, or the economic power consumption level, it is inseparable from the support of heat dissipation. The heat dissipation determines both the upper and lower limits of the motor.

For example, permanent magnet synchronous motors rely particularly on heat dissipation because their rotors use permanent magnet materials, which are at risk of complete demagnetization at high temperatures and are irreversible.

 

AC asynchronous motors, on the other hand, will cause the rotor to use a traditional coil winding structure, which will cause it to dissipate greatly when running at full load  Excessive temperature will not only melt the various insulation materials inside, but even melt the windings in extreme cases.

Therefore, in order to ensure that it does not overheat, many car companies strictly limit the motor speed, which leads to many trams unable to play the ultimate acceleration, extreme speed and other performance; Only when heat dissipation is improved, the motor has the possibility of unlimiting and continuing to develop upward.

 

What should a good motor heat dissipation look like?

 

At present, many car companies are improving the technical layout of motor heat dissipation capacity, focusing on flat wire motors, lamination processes, and oil cooling systems.

 

Flat lines replace round lines

Compared with the traditional round wire motor, the flat wire motor can not only improve the work efficiency by about 10%, but also increase the heat dissipation capacity by 10%, which can be said to be an all-round improvement.

 

In the round wire motor, the stator winding is composed of many round copper wires, which has limited ability to share the current, and the space utilization is not high, which will release more heat.

Flat wire windings completely fill the slot space in a simple stacking manner by using rectangular copper strips, and the current can be distributed by the thicker diameter and larger surface area of the flat wire, thereby reducing heat generation.

 

In this regard, Tesla's Model 3 and Model Y equipped permanent magnet synchronous motors use 10 layers of flat wire winding, although the more flat wire windings are not necessarily better, but while improving heat dissipation, Tesla's low power consumption, high speed, it is difficult to say that there is no credit for these 10 layers of flat wire windings.

 

A lamination process is used

 

The motor rotor structure using the lamellar layer process looks like countless cucumber slices are put together into a whole. Car companies choose to cut the rotor into countless thin slices, reducing the volume of the rotor while reducing the generation of current loops, and the sheets are connected by welding and other processes.

But the biggest beneficiary of the lamination process is the permanent magnet embedded in it, because it is the most sensitive to high temperatures. Just the rotor

When the temperature is controlled, the pressure of the permanent magnet can be much smaller. In this regard, BYD's motors can be referenced, in addition to using the lamination process, BYD even added a small amount of silicon to the production material of the rotor sheet to change the conductivity of the rotor, thereby controlling the heat.

 

Replace water cooling with oil cooling

 

Oil cooling can penetrate deep into places that water cooling cannot reach, and it is not conductive and magnetic, and can directly penetrate into the internal area of the motor that many water-cooled pipelines cannot penetrate, which can greatly improve the heat dissipation capacity.

 

In this regard, the average peak temperature of the oil-cooled motor of the M5 can be reduced by 30°C, which can enable the motor to obtain a stronger performance ceiling and continuous ability, such as zero hundred acceleration repeated acceleration 15 times without attenuation, long-term high-speed driving is more stable, etc. Minus, long-term high-speed driving is more stable, etc.

 

Summary --

Many car companies and motor suppliers at home and abroad are actively promoting the corresponding technology and process around the heat dissipation performance, in fact, there is still a lot of room for optimization, and some have achieved good results, but because the cost cannot be reduced in a short period of time, so it cannot be mass-produced. With the gradual decline of related technical materials and process costs, the heat dissipation performance of the motor will eventually improve steadily, and after completely lifting the seal of "heat dissipation", the overall performance of the motor will really be qualitatively changed.