Outer Rotor BLDC Motor Design: Your Easy Guide to Electric Motor Modeling

An outer-rotor brushless DC motor is a strong kind of electric motor. In this design, the magnets on the rotor spin on the outside of the stator windings. This gives them special abilities, like high torque. This article is for you. It will help you learn how to design a better outer-rotor brushless DC motor. We will show you how computer modeling can make your motor design steps easier and help you succeed. You will learn the main steps to improve your BLDC electric motor so it works its best.

What Is an Outer Rotor BLDC Motor?

A brushless direct current motor (BLDC motor) is a common kind of electric motor. People like it because it works well and you can count on it. Most motors you see have the rotor spin inside the stator. This is called an inner-rotor design.

An outer-rotor brushless DC motor is different. The rotor has permanent magnets and it is on the outside. The stator and its winding coils are on the inside. This motor design means the rotor is wider. This change is a big plus for the outer rotor BLDC motor. It gives it high torque. The magnetic force pushes from farther away from the middle. This makes the turning force, called torque, much stronger. This makes this bldc motor great for things like drones, electric bikes, and fans.

Why is Good Modeling the First Step for Your Motor Design?

You need a plan before you build a real BLDC motor. In motor design, this plan is a computer model. Modeling means you make a copy of your brushless DC motor on the computer. This is a very big step.

Good modeling helps you save a lot of time and money. You do not have to build many real test motors. Instead, you can try out hundreds of design ideas on the computer. This modeling lets you see how your BLDC motor will work before you even make one. You can see how strong it is, find its weak spots, and make its good parts even better. A good motor model is the starting point for a great motor design. Without good modeling, you are just taking a guess. With good modeling, you can be sure your design and performance will meet your targets. This is why all new electric machines are made using this kind of smart modeling.

What Main Parts Should You Model?

When you start modeling your BLDC motor, you need to set up its main parts. We call these parts design parameters. Each parameter changes the motor’s final torque and how well it works. It is very important to get these parameters right for a good motor design.

Here are some of the most important design parameters you need to put in your modeling:

Your motor design needs to find a good mix of these design variables. For example, a bigger magnet thickness can give you more torque, but it might make the bldc motor too heavy. Modeling helps you find the optimal design for what you need.

How Does Finite Element Method (FEM) Modeling Work?

How can a computer understand a BLDC motor that has so many parts? The answer is the Finite Element Method (FEM). This is a strong modeling tool. FEM cuts the motor design into thousands of small bits. These bits are called “finite elements.” It then uses math to figure out how the magnetic fields act in each small bit.

By figuring this out for all the bits, the FEM software can make a very clear picture of the whole bldc motor. It can show you the magnetic flux density in every area of the stator and rotor. The finite element method is the best way to see just how your brushless DC motor will work. This deep check is much better than simple math rules. This is because it can understand complex shapes and how materials act. Using FEM is a big step to optimize your motor design.

Can You Use Ansys for Your BLDC Motor Modeling?

Yes, you can. Ansys is a very common and strong software tool for FEM modeling. Many engineers use Ansys to design and test electric machines. This includes the outer-rotor brushless DC motor. Ansys lets you build a full computer model of your BLDC motor. You can set every parameter, from the magnet type to the details of the winding.

After your motor model is built in Ansys, you can run tests on the computer. These tests are like a test on the computer. The software will show you how much torque the bldc motor makes, its output power, and how well it works. The simulation results from Ansys are results you can trust. They help you make smart choices to make your motor design better. Ansys is a great tool for any serious motor for electric vehicles or other uses. The FEM modeling power of Ansys is top-notch.

How Do You Pick the Right Materials in Your Modeling?

The materials you pick for your BLDC motor are a big deal. The right materials lead to high efficiency and better motor performance. Your FEM modeling must have information about these materials. The most important thing about a material for a BLDC motor is its magnetic behavior, or how it acts with magnets.

For the rotor, you will use permanent magnets. The magnet type, like Neodymium (NdFeB), makes a big difference. For the stator, you will use a special steel. The way this steel acts is shown by something called a B-H curve. The B-H curve tells the modeling software how the material acts in a magnetic field. It is important that the magnets are magnetized to the saturation point. A B-H curve shows this point in a closed circuit. This detailed modeling helps you guess the iron losses. It also makes sure your bldc motor works the way you think it will. Using the correct B-H curve in your FEM modeling is very, very important for getting true simulation results.

How Can You Improve Your Design for the Most Torque?

One of the best reasons to use an outer-rotor brushless DC motor is to get high torque. So, a common goal is to get the maximum torque you can from your motor design. Modeling is how you do this. To get the maximum torque, you need to test different design variables.

Using your FEM modeling software, you can run tests. These tests show how changing each parameter changes the torque.

• What if you make the magnet thickness bigger? Your modeling might show a 10% jump in torque.
• What if you make the air gap smaller? Your FEM check will show a stronger magnetic pull and more torque.
• What if you change the number of poles? The simulation results will tell you the new torque at a different rated speed.

You can run hundreds of these tests on the computer. This process of trying and changing things is called design optimization. It helps you find the best mix of design parameters to get the maximum torque from your BLDC motor. This is very needed for things like electric vehicles where a lot of torque is needed.

What is the Goal of Design Optimization for High Efficiency?

Getting maximum torque is great. But it is not the only goal. You also want your brushless direct current motor to have high efficiency. A motor with high efficiency uses electric power well. It turns it into useful output power. It wastes less power as heat. This is a very big deal for things that use batteries, like drones or electric cars.

To get higher efficiency, you need to lower the losses in the bldc motor. The two main kinds of losses are copper losses (in the winding) and iron losses (in the stator). Your FEM modeling can guess both of these. The design optimization for efficiency might mean you do these things:

• Change the winding to use a thicker wire, which lowers copper loss.
• Pick a better kind of steel with a better B-H curve to lower iron losses.
• Find the optimal design that gives a good amount of torque and also has high efficiency.

Sometimes, trying to get the most torque can lead to lower efficiency. This is where multi-objective optimization can help. This smart modeling tool helps you find a motor design that has both great torque and works very well. It finds the optimal values for what you need.

How Do You Study the Test Results from Your Modeling?

After your FEM modeling software runs a test, it gives you a lot of data. These are your simulation results. It is very important to know how to read these results to make your motor design better. The analysis results often show up as graphs and color maps.

For example, a color map of your BLDC motor can show the magnetic flux density. You can look for spots where the magnetic field is too weak or too strong. A graph might show the torque of the motor while it spins. You can check if the torque is steady or if it goes up and down. By looking at these analysis results, you can find problems. Maybe the shape of the stator is causing extra iron losses. Or maybe the magnet thickness is not enough to make the rated speed and torque. The simulation results show you what to do next to optimize the bldc motor. Remember, like it says in papers like the proceedings of the 2019 international conference on electrical machines and systems, the opinions and data contained in all publications are often just from that one writer. This means you must be able to understand the FEM modeling data yourself.

What Are the Last Steps in the Design and Work Check?

You have built a model. You have run tests on the computer. You have looked at the results and made changes. Your modeling now shows you have a great motor design with high output power. What is next? The last step is to check how the motor works in total. This is the motor performance. You should have a final motor design that meets all your targets.

This is where you do a last check of your optimal design. The modeling should make sure that you have reached your goal for maximum efficiency and torque. It is also a good idea to check how the bldc electric motor will work in other situations. What happens if it gets warm? Your modeling can help guess this. Many papers, like the proceedings of the 2018 international conference on electrical machines and systems, show different design ideas. It is important to know that data contained in all publications are just from those researchers. Your own FEM modeling and study are what really prove your design is good and ready. This last check using modeling makes sure the performance of BLDC motors will be great when you finally build a real, working motor.

Cose fondamentali da ricordare

• An outer-rotor BLDC motor design gives you high torque because the rotor is on the outside.
• Modeling is the first big step. It saves time and money because you can test your bldc motor on a computer first.
• The Finite Element Method (FEM) is a strong modeling tool that gives very true results about the magnetic fields in your bldc motor.
• Software like Ansys helps you build a motor model and run tests to check motor performance.
• Design optimization is how you change design parameters (like magnet thickness or air gap) to make the bldc motor better.
• Your main goals are usually to get maximum torque and high efficiency by cutting down on losses.
• Looking at simulation results from your modeling shows you how to make your motor design better to create the best brushless DC motor.