SynRM | A new giant in the electrical world

Did you know that synchronous reluctance motors that were invented in the late 20th century are now considered superior to induction motors? These motors have advanced electronic controls that make their efficiency and torque output far superior to any other motor in many industries and even in the company named after the inventor. of the induction motor tesla has started switching to syn rm motors tesla uses an advanced version of the synarm motor let's look at the physics and design features of this new

giant

in the

electrical

world

the physics of this motor is quite simple, there may be observed this interesting phenomenon when a magnet is within the range of iron nails, the nails are attracted towards it to understand the reason behind this response, we have to understand two things first, the magnetic field chooses the path with the least resistance and second, the structure of iron, let's explore the resistance. the magnetic field has to deal more specifically with this resistance is called reluctance.

Magnetic flux always has a tendency to flow through the path of least reluctance. The maximum magnetic flux passes through iron instead of air because the reluctance value of iron is much less than the reluctance value of Air Now, let's learn about the structure of iron. Iron has a domain-based structure. Domains are small areas with individual magnetic poles. However, as you can see, these poles are naturally arranged in a random direction, so if you add up the total magnetic field, it cancels out a The typical domain area is the result of atoms with unpaired electrons spinning in the same direction, As shown in this image, as the magnetic flux of the permanent magnet flows through the iron nail, its domains align in a single direction, once that alignment occurs, the entire iron nail will have a resulting magnetic field and It acts like another permanent magnet, therefore an attractive force is generated between the nail and the permanent magnet.

However, for the domain to be aligned, the existence of an external magnetic field is mandatory, so it is more accurate to call the iron nail a temporary magnet let's do an experiment and generate a torque using the concept of reluctance force that we just learned a solid iron bar that can rotate freely is positioned as shown now let's keep an electromagnetic displaced with respect to the iron bar the iron bar It will definitely be attracted to the electromagnet due to the reluctance force and will rotate; However, after aligning with the magnetic field, the torque on the iron bar becomes zero.

This is a crucial concept to keep in mind when the iron bar and the magnetic field are perfectly aligned the torque on the rotor will be zero now let's design a simple synchronization using the fundamentals we have developed so far here a three phase coil arrangement replaces the electromagnet when a three phase alternating current passes through this coil it will produce a magnetic field which is rotating can you say what will happen to the iron rod under the influence of this rotating magnetic field? A simple answer is that the rotor will align with the magnetic field as we learned in the previous experiment and spin at the same speed as the magnetic field. field, this answer seems quite logical, however, when you apply a rotating magnetic field to a stationary rotor, the results may surprise you, the rotor actually resists rotation.

Let's learn why as the final pole approaches above the rotor, the domains of the iron bars begin to align as shown and the opposite poles will have an attractive force between them then the rotor must rotate, the rotor rotates but the villain here is the inertia of the rotor which causes it to reach a very low speed compared to the rmf, at which point the next s pole will meet the rotor causing a repulsive action, well you might think that because there are no permanent magnets the induced poles in the rotor can change as the rmf changes, however they do not, here is the capture of the magnetic domains we learned earlier, they actually take time to rotate this .

It is a well-known phenomenon called hysteresis, therefore, when the south pole approaches, the rotor poles cannot change quickly, resulting in a repulsive force due to the inertia of the rotor and hysteresis, a still rotor is subject to alternating attractive and repulsive forces. This is why sin RMS is not inherently self-starting, therefore, the most adopted way to make this motor start automatically is to reduce the rmf speed during starting and then gradually accelerate it. Let's try this method. We can easily control the rmf speed by varying the input frequency. Initially, the rmf velocity is almost zero. A magnetic pole of opposite polarity is induced in the rotor and is attracted by the rmf and starts slowly.

The controller device detects the position of the rotor depending on this position. The controller adjusts the rmf speed so that there will always be an attractive force between the rotor and the rmf as the rotor accelerates, the controller also increases the speed of the rmf, so the rotor runs in sync, in addition to starting the motor, the controller plays a crucial role in the normal functioning of the system and in the We have seen that if the iron bar is aligned with a magnetic field, the torque produced will be zero. Here is a hypothetical job with zero load on the rotor.

By adding a load to the motor, the rotor rotates behind the field at an easterly angle. The angle is known as the load angle. Now suppose the load on the motor were to increase abruptly, obviously the load angle will also increase; However, if the load angle crosses a critical limit, the rotor will go out of sync and stop. The controller reaches the stopping point. Rescue in such situations Continuously measures the position of the rotor Efficiently adjusts the angle and magnitude of the alternating current and ensures that the charging angle is always below the critical limit Clearly synchronized They are software driven by just adding an iron bar More perpendicularly we can produce double the amount of torque.

Keep in mind that such a rotor has to use a 4-pole rotating magnetic field. Now let's look at another crucial concept related to timing. You can see that the interaction between the magnetic field and the rotor area is high at this angle and low. at this angle, the difference in flux interactions results in the production of reluctance torque, which means that to further increase the reluctance torque, a maximum flux interaction is necessary in the left side alignment with a flux interaction very low in right side alignment. a perfectly round rotor design will result in maximum magnetic flux interaction;

However, such a design does not have a minimum flow interaction position, the flow is constant at all angles to understand how to produce a minimum flow interaction design, let's use fea simulation, fea em software. solidworks works 2d accurately simulates the shape of the rotating magnetic field. Now let's place alternating layers of a ferromagnetic material and a non-magnetic material along the magnetic field lines. This design will obviously produce a high flow interaction at this angle. What is interesting is that when the rotor is offset by 45 degrees, the flux interaction becomes extremely low due to the non-magnetic barriers, the rotor experiences greater reluctance in this position.

This is a perfect design from an

electrical

engineering perspective; However, when engineers tested this design they observed that the rotor failed. mechanically at higher speeds, since the bond between different layers does not provide the necessary centripetal force, in addition, the manufacture of such radially stacked rotors is quite rigorous, for this reason modern synthetic systems use a slightly different design, a rotor design Based on thin laminations, the fabrication of this design is quite easy while maintaining the same good electrical qualities. Here curved cavities are drilled into the thin laminations. Additionally, the natural air between these cavities acts as a magnetic insulating material.

Synrms has begun to replace induction motors in most industries due to its A notable performance in induction motors is torque produced due to the interaction between the rmf and the current flowing through the rotor bars. This current flow results in considerable amounts of i-squared r losses in the form of heat, which is why induction motors have a lower efficiency compared to syn rms due to the absence of r i-squared loss and

synrm

s. They run cooler for the same current input. Synrms are capable of producing 10 to 15 percent more torque than induction motors. Finally, the most obvious advantage is that

synrm

s always work.

At synchronous speed, the rmf speed in an induction motor, the rotor speed will be slightly less than the synchronous speed and this speed varies depending on the load. We hope you now have a good understanding of how synchronous reluctance motors work the next time you attach a magnet to your refrigerator you will know that it attracts due to the same reluctance force. We thank the workers for their support in this video. Don't forget to press the support button. Thank you.