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How to improve the performance of motors?

Date:2023-09-12   Author:XINDA MOTOR

In this article, we’ll take a closer look at how to improve your motor’s performance.

Traditionally, there have been two directions in motor design: copper motors and iron motors. Copper motors use electric field as the main source of motor torque, which involves the current (I) and the number of enameled coils (N) in the motor torque formula. Therefore, the design of copper motors usually requires more enameled wires, which has become the current Mainstream design trends. In comparison, iron motors use a larger silicon steel sheet area and less enameled wire, using the space size to obtain motor torque. However, due to their large size and low energy density per unit area, ferroelectric machines are not popular in the market.

1. Copper motor and iron motor

Therefore, it is not difficult for us to judge that copper motors have a higher copper loss ratio, while iron motors have a higher iron loss ratio. If we look up the commonly used magnetic conductive material "silicon steel sheet" in motors, we will find that the iron loss is marked in W/KG, which shows that the iron loss is related to the weight of the silicon steel sheet. Therefore, the iron motor uses a larger size of silicon steel sheet, which also means that the weight of the silicon steel sheet is heavier, so the iron loss is higher.

2. Replace with larger silicon steel

To reduce iron loss, the general method is to replace the silicon steel sheet; but for motor designers, the first task is to confirm the magnetic field state inside the silicon steel sheet. In the iron loss equation, we can see various forms of energy loss and find corresponding solutions.

However, there is a hidden loss that cannot be ignored and is "magnetic leakage". This magnetic leakage phenomenon will cause the motor torque to decrease and may even cause electromagnetic interference. There are two solutions to this magnetic flux leakage phenomenon. The simplest is to replace the silicon steel sheet with a larger one, so that the contact area with the magnetic lines of force is larger and the magnetic flux leakage is reduced.

3. Optimize magnetic field lines

In addition to replacing silicon steel sheets, magnetic flux leakage can also be avoided by optimizing magnetic lines of force. Looking at the picture below, we can see that a small number of magnetic field lines deviate from the normal path. This is what we generally call magnetic flux leakage. This phenomenon may cause the motor's torque to decrease and may even produce electromagnetic interference.

Figure (3)

When the magnetic flux carrying capacity of the silicon steel sheet is not enough to carry too much magnetic force, it may cause magnetic flux leakage. For this reason, we can of course increase the size of the silicon steel sheet so that it can carry more magnetic force. However, the magnetic intensity of silicon steel sheets is limited, which is the bottleneck encountered in recent motor design. As the magnetic force of magnets continues to increase, designers can easily choose magnets with high magnetic force. However, the load-bearing capacity of silicon steel sheets is not Relatively improved options.

At the same time, the theory of magnetic resistance tells us that magnetic field lines always tend to choose the path that is easiest to pass. So when a magnetic field line finds a better path than the one planned by its designers, it changes direction. For example, you can see in the picture that some of the magnetic field lines span the groove instead of going around the yoke. This is like when running on the playground, we would choose to cross the grass in the middle instead of walking in a large circle. Although sometimes this magnetic flux leakage is unavoidable, as motor designers, we should strive to reduce the occurrence of magnetic flux leakage by adjusting the motor magnetic field to optimize the magnetic lines of force.

Therefore, in addition to directly reducing iron losses, we can also improve the efficiency of the motor by properly planning the energy path within the magnetic field.

Figure (4)

Summary points:

The use of magnetic energy must comply with the principle of minimum effort. The silicon steel sheet should utilize magnetic lines of force as much as possible to avoid magnetic flux leakage.