Three Phase Induct Motor

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FAQ

How Does a Brushless Electric Motor Work?

By: Marshall Brain

 

The armature of a typical DC motor

The article How Electric Motors Work explains how brushed motors work. In a typical DC motor, there are permanent magnets on the outside and a spinning armature on the inside. The permanent magnets are stationary, so they are called the stator. The armature rotates, so it is called the rotor.

The armature contains an electromagnet. When you run electricity into this electromagnet, it creates a magnetic field in the armature that attracts and repels the magnets in the stator. So the armature spins through 180 degrees. To keep it spinning, you have to change the poles of the electromagnet. The brushes handle this change in polarity. They make contact with two spinning electrodes attached to the armature and flip the magnetic polarity of the electromagnet as it spins.

This setup works and is simple and cheap to manufacture, but it has a lot of problems:

The brushes eventually wear out.

Because the brushes are making/breaking connections, you get sparking and electrical noi

The brushes limit the maximum speed of the motor.

Having the electromagnet in the center of the motor makes it harder to cool.

The use of brushes puts a limit on how many poles the armature can have.

With the advent of cheap computers and power transistors, it became possible to "turn the motor inside out" and eliminate the brushes. In a brushless DC motor (BLDC), you put the permanent magnets on the rotor and you move the electromagnets to the stator. Then you use a computer (connected to high-power transistors) to charge up the electromagnets as the shaft turns. This system has all sorts of advantages:

The poles on the stator of a two-phase BLDC motor used to power a computer cooling fan. The rotor has been removed.

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Because a computer controls the motor instead of mechanical brushes, it's more precise. The computer can also factor the speed of the motor into the equation. This makes brushless motors more efficient.

There is no sparking and much less electrical noise.

There are no brushes to wear out.

With the electromagnets on the stator, they are very easy to cool.

You can have a lot of electromagnets on the stator for more precise control.

The only disadvantage of a brushless motor is its higher initial cost, but you can often recover that cost through the greater efficiency over the life of the motor.

 

What requirements should the technical data of the motor products have?
1. Basic parameters: The technical data of motor products should contain basic parameters, such as rated power, rated voltage, rated frequency, rated current, speed, etc.

2. Product functional characteristics: The functional characteristics of the product should be clearly described, such as reliability, noise, protection level, environmental adaptability, etc.

3. Product specifications: Technical data should contain detailed specifications of the product size, weight, installation method, connection method, etc., so that the user can choose and use the product.

4. Product material and process: Material and process have direct influence on the performance and life of the motor, so the material and process of the product is also an important technical information content.

5. Product installation, use and maintenance instructions: The manual should introduce in detail the methods and steps of product installation, use and maintenance so that users can install and use the motor correctly and ensure its long-term stable operation.

6. Product accessories or accessories: If the product has accessories or accessories, they should also be introduced in detail in the technical data to facilitate users to understand and purchase.

 

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