Engineering Behind Tesla s Motor – Tesla Model 3
In this article we will learn About the Tesla s Motor – Tesla Model 3, So let’s Start – When developing the Tesla Model 3, engineers made a stunning design choice: they abandoned the conventionally used and well-proven induction motors in favor of a new type of motor called the IPMSynRM. These motors have a completely different design that uses both magnetic and reluctance action. The big news is that tesla motors have begun replacing induction motors in their vehicles.
How do these motors work?
What’s so special about the IPMSynRM?
Let’s look into that. To get a clear response, we must first understand the electric motor in the model s, which is an induction motor as you can see by the rotating component.
Alternating currents from the battery packs flow into the motor’s outer windings, creating a spinning magnetic field. The oscillating field interacts with the rotor bars, generating electromotive forces that cause currents to flow through them.
The interplay of these generated currents with the RMF exerts stress on the rotor bars, spinning the rotor. These motors are efficient, but not up to par. For example, long drives at cruise speed lose three to four percent of energy to generate currents in the rotor bars, which is clearly inefficient.
Despite the fact that induction motors have a higher beginning torque than IC engines, there is a motor technology based on permanent magnets that gives even higher starting torque from the same motor volume. PM motors work by attracting two magnetic fields; they give a decent starting torque when controlled by a controller, and they have no energy waste in the rotor. Wrapping permanent magnets around a solid iron cylinder produce an efficient permanent magnet rotor.
Why not replace the squirrel cage-type rotor with a permanent magnet one?
With a little understanding, the combined magnetic field of these four permanent magnets may be displayed as shown. Now we must investigate the interaction between the RMF and the combined magnetic field. For example, notice how the south and north poles interact with each other while evaluating force interaction between two magnetic fields.
Let’s hide the magnetic field produced by the permanent magnets and only show the force interactions between the north and south poles. At this angle, the RMF obviously creates a torque on the rotor.
Now spin the RMF to 45 degrees. Surprisingly, the rotor experiences maximum torque at this angle since the attracting and repulsive forces are practically tangential to the rotor and produce torques in the same direction.
The reason why tangential forces produce maximum torque is clear using this simple ball analogy, so this is the ideal angle to start your electric car. Maintaining this angle or further angle regulation is the smart controller’s job in this design because the rotor has no induced current, which reduces the input energy required and leads to higher efficiencies than induction motors. The pm motor runs at synchronous speeds as well, but the search for the ideal electric motor is far from over.
As you start the automobile or ride up a hill, a permanent magnet motor provides a lot of torque; however, when you drive down the road at high speeds, permanent magnet motors perform poorly. The back emf is the villain here; the permanent magnets’ magnetic field lines connect with the stator windings and generate an emf; this emf is known as back emf, and it is clearly a reverse voltage to the stator’s supply voltage the greater the rotor speed.
The more back emf it creates, the worse permanent motors perform in high-speed applications. Furthermore, these high-strength magnets cause magnetic eddy current losses, which raises the temperature of the machine.
How we can modify this design so that it will work efficiently even at high speeds?
to operate at a high rate Tesla engineers took advantage of iron’s reluctance property. Reluctance refers to a medium’s ability to resist magnetic fields. Due to the reluctance force, an iron nail attaches to a permanent magnet, but air does not. An interesting occurrence can be noticed when slots are cut in the iron at this rotor position when the rotor is in a high reluctance state.
The rotor always has a tendency to acquire a low reluctance state, thus if the magnetic field rotates, the rotor will rotate with it, so the rotor can always be in a low reluctant condition. The rotor’s rotation speed will be the same as the RMF speed. The torque produced by this phenomenon is known as synchronous reluctance torque, and such motors are known as synchronous reluctance motors.
In short, permanent magnet motors are good at low speeds and synrms are good for high speed operations. If we can include synrm technology into the permanent magnet motor we saw earlier, a motor that uses both reluctance and permanent magnet effects could run at any speed efficiently.
The permanent magnets can be easily integrated into the synrm motor’s slotted cuts deep within the iron core, further reducing the magnet’s effect on the stator winding and thus reducing back emf. This design is the internal permanent magnet synchronous reluctance motor, also known as the Tesla Model 3 motor.
Because the magnets’ relative permeability is nearly equal to that of air, they will resist the field’s passage through them, just as air did before, resulting in reluctance torque. To properly analyze this motor, we must first observe the resultant magnetic field produced by the permanent magnet arrangement.
The FEA software em works 2d in conjunction with SolidWorks comes to the rescue. The resultant magnetic field created by this configuration will be as illustrated. If these magnets were put far apart, each one would generate its own magnetic field, as seen in the illustration on the left.
Let’s continue our investigation. The permanent magnet and reluctance components of this motor have completely distinct behavior depending on the location of the RMF, which is an interesting feature of this design.
Permanent Magnet Torque
Let’s look at each one separately from our most recent IPMSynRM design. If the RMF is rotated by 45 degrees, a torque acts on the magnets in a clockwise direction due to the effect of the RMF at this angle, the permanent magnets will not experience torque because there is no tangential component for these four forces, and the torque the remaining forces produce cancel each other out. If the RMF is rotated by 45 degrees, a torque acts on the magnets in a clockwise direction due to the effect of the RMF at this angle Let’s see what happens.
What happens when we turn it by another 45 degrees the torque?
The torque curve of the permanent magnet can be obtained by reducing the rotor’s output to zero. In the same manner, the iron component of the rotor produces the opposite effect.
Let’s take a look: at the initial angle, the torque produced will be zero because the RMF is perfectly misaligned and symmetrical; when we slightly offset the RMF in a clockwise direction, the rotor will experience a negative and maximum torque; when the RMF reaches 45 degrees, the torque becomes zero again because the RMF is perfectly symmetrical; and as we rotate the RMF further, the reluctance torsion will
Let’s look at the motor in the Tesla Model 3 or the combined permanent magnetic and reluctance effect on the motor. The total torque graph clearly shows that if the rmf angle is around 50 degrees, we’ll get the most torque from the motor, so Tesla engineers made sure that when you start the car, the rmf angle is around 50 degrees, ensuring maximum torque generation.
We know that as the motor speed increases, the permanent magnets induce a back emf on the stator coils. To solve this problem, tesla motors devised a simple solution for turning at high speeds: they align the rmf opposite the permanent magnetic field. As you can see, the rmf weakens or almost cancels the permanent magnetic field. This way, even at high speeds, such motors will not produce m.
Model 3 has a 6-pole design, which is identical to a 4-pole design except for the increased torque. Tesla Motors isn’t the first business to develop a cutting-edge motor.
The Toyota Prius, a hybrid electric vehicle, employs comparable IPMSynRM motor technology, with two IPMSynRM machines, one for driving the vehicle and the other for generating power. The magnets in the Model 3 and Prius motor designs are a noteworthy contrast. Solid magnets are used in Prius motors, however, each magnet in model 3 motors is divided into four sections. This segmentation lowers eddy currents in the magnets, preventing them from overheating and demagnetization, as well as keeping the motor cooler.
The IPMSynRMmotor in the 2019 edition of the Model S automobiles offers efficiencies of up to 96 percent, compared to typical induction motors with efficiencies of up to 94 percent. It’s difficult to keep the rotor of an induction motor cold. IPMSynRM does not have this problem, and because of the reluctance, they have larger torque values than induction motors. IPMSynRM has unquestionably raised the bar in the EV world.
We hope you enjoyed this explanation of how clever design decisions gave birth to a promising electric motor.