What is the difference between permanent magnet synchronous motor and induction asynchronous motor?
In this era when new energy vehicles are gradually emerging, the driving motor is as important to new energy vehicles as the engine is to fuel vehicles, because it not only determines the speed of vehicle startup, but also determines the acceleration performance of the vehicle. Because of this, many car manufacturers now pay great attention to the research and development of motors, which is the new favorite of the majority of car companies.
At present, there are mainly two types of vehicle motors that can be promoted and used in the field of new energy, and they are permanent magnet synchronous motors and AC asynchronous motors. Among them, the former is quite popular with domestic new energy car companies and has been widely used, while the latter is not so lucky. Not to mention domestic, there are only a handful of users worldwide.
So, why can the permanent magnet synchronous motor win the favor of so many new energy and traditional car companies? What is the difference between permanent magnet synchronous motor and AC motor? Why don’t Tesla and Weilai use permanent magnet synchronous motors? Let’s listen to the professor’s next words!
What is the difference between permanent magnet synchronous motor and AC asynchronous motor?
1. Different structure settings
From a structural point of view, the structure of the permanent magnet synchronous motor is more complicated than that of the AC asynchronous motor, and the cost output is relatively high, but the permanent magnet synchronous motor is relatively small in size and light in weight.
Permanent magnet synchronous motor is mainly composed of rotor, end cover and stator. Its stator structure is very similar to that of ordinary induction motor. However, its rotor structure design is very unique. High-quality permanent magnet poles are placed on the rotor. A rotating magnetic field can be generated.
As for the structure of the asynchronous motor, it can be divided into two parts: the stator and the rotor. Of course, in addition to these, there are also auxiliary parts such as end covers and fans. It is worth noting that since the stator of the asynchronous motor generates an exciting rotating magnetic field and absorbs electric energy from the power supply at the same time, its stator is an armature.
2. The working principle is different
At the level of working principle, the permanent magnet synchronous motor is excited by the permanent magnet to generate a synchronous rotating magnetic field. The three-phase stator winding reacts through the armature under the action of the rotating magnetic field to induce a three-phase symmetrical current. At this time, the kinetic energy of the rotor is converted into electrical energy, and the permanent magnet synchronous The motor is used as a generator;
Conversely, when the three-phase symmetrical current is passed into the stator side, since the three-phase stators are 120 degrees apart in space, the three-phase stator current generates a rotating magnetic field in space, and the rotating magnetic field of the rotor moves under the influence of electromagnetic force, converting electrical energy into kinetic energy of the rotor , The permanent magnet synchronous motor is used as a motor.
AC asynchronous motor is to pass symmetrical alternating current to the three-phase stator winding to generate a rotating magnetic field to cut the rotor winding, thereby generating an induced current in the rotor winding, and the current-carrying rotor conductor generates an electromagnetic force under the action of the stator rotating magnetic field to act on the motor shaft to form an electromagnetic force. The torque drives the motor to rotate in the direction of the rotating magnetic field.
It is worth noting that when the conductor cuts the magnetic field lines in the magnetic field, an induced current will be generated inside the conductor, and then work hand in hand with the induced magnetic field to apply a driving force to the rotor of the motor to push the rotor to move.
What is the difference between permanent magnet synchronous motor and induction asynchronous motor
Why are permanent magnet synchronous motors more popular than AC asynchronous motors?
According to the characteristics of permanent magnet synchronous motors and AC asynchronous motors, permanent magnet synchronous motors are more suitable for frequent start and stop conditions, while AC asynchronous motors (induction motors) are more suitable for high-performance and high-speed working conditions, which is why The reason why high-performance electric vehicles such as Tesla and Weilai all use AC asynchronous motors.
Judging from the characteristics listed in the table, the reason why the permanent magnet synchronous motor can be favored by most car companies seems to be very simple. It is better than the AC asynchronous motor, which is of great benefit to improving the energy efficiency of the vehicle and extending the cruising range.
But then again, although the AC asynchronous motor does not have an advantage in terms of weight and volume, it has a wide speed range, low manufacturing cost, and simple process. It is not easy to cause the motor to lose its magnetism during operation. It is a bright spot that permanent magnet synchronous motors do not have.
On the other hand, the permanent magnet synchronous motor can still guarantee an energy conversion efficiency of about 95% in the instantaneous state, and because the motor is small in size, light in weight and does not require an efficient and complex cooling system, it can effectively and maximize the use of the vehicle The spatial layout plays a very important role in the design and manufacture of the vehicle.
Secondly, because the core technology of electric motors is basically monopolized now, the electric motors used by many domestic car companies are provided by suppliers, and the only car companies that can independently own the independent property rights of electric motors are BYD, Roewe, Weilai, and Tesla. These few, this number is not an exaggeration even if it is described as few stars.
Of course, in addition to technical characteristics and market reasons, the raw materials used in the two motors cannot be ignored. It should be known that permanent magnet materials such as NdFeB used in permanent magnet synchronous motors are important rare earth resources, but rare earth resources in Europe and the United States are very scarce; in contrast, my country has 70% of the world’s rare earth resources, and the NdFeB magnetic materials The total output accounts for 80% of the world’s total, so it’s up to you to decide which one is stronger and which one is weaker.
The book returns to the main story, as the two most popular drive motors used by current car companies, there is no difference between permanent magnet synchronous motors and AC asynchronous motors, but they are different in what they are good at. For car companies, they often consider different things, and naturally choose different motor objects.
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