Brushless Motors: How They Work

Let's take a look inside this beast motor to find out how it functions. The rotor consists of four permanent magnets with alternating opposing polarities and 12 coils that utilize the metal case as a heat sink to improve the lifespan.

For simplicity, let's use one magnet with six coils. The three coil pairs which are also connected in series and with a reverse winding direction are bonded together through a star connection, which is not a surprise, given that the label of my motor already said so.

Now, we need to energize two coil pairs one after the other in these six steps to create a complete rotation of the rotor. While the DC motor uses the mechanical principle of a commutator to create rotating fields, the brushless motor uses an electrical one, also called the ESC (Electronic Speed Controller).

You can get different variations with, for example, software to program them and all kinds of different features. But in the end, they all do the same thing - by applying a control voltage to the input, aka the yellow wire, I can set two reference points which are basically just different lengths of a voltage burst in order to adjust the frequency in which the motor rotates.

In these six steps for one complete rotation, repeats obviously a higher frequency means less time for one rotation and thus a higher RPM. The three states of the outputs are high, low, and floating, which is realized through an array of P-channel and N-channel MOSFETs. The number of parallel MOSFETs for one output in this case six of them directly determines how much current your driver can handle - more of them means more current and thus your motor can be more powerful.

But the price also increases, and the overall current draw is also determined by the load which is attached to the shaft. The amount of voltage applied to the ESC and also regulated by a controller with modulation of the different output states.

Getting back to the practical example, if I set a constant frequency of around 65 Hertz, I can use my tachometer to measure an RPM of around 1,740. If I divide that by 60, I get a frequency of only half the original one - why? The reason is the double number of coils and especially the permanent magnets which cause a lower RPM but on the other hand, a bigger torque.

This is also the reason why OutRunner brushless motors are preferred when high torsional moments are necessary. Due to more space on the outside, they simply can accommodate a higher amount of magnets and thus like I already said, they can achieve a lower RPM and a higher torque at the same frequency.

Finally, let's talk about the KV rating which stands for RPM per volt applied. Let's use a 7.4 and 11.1 volt battery as an example with the 520 KV motor. I reached a maximum RPM of 3,750 and 5,644 while with the 920 KV1 I reached a maximum of 6,780 and 10,500 - so it is true that with a higher KV rating you get more RPM and by calculating with the ratings we get values which are definitely close enough to reality.

But in the end, it's not mainly about the voltage which determines the rotation speed - it's about a higher frequency of the ESC that can be achieved with a higher voltage and depends on the characteristic properties of the motor.

WEBVTTKind: captionsLanguage: enin a previous project I showed you how to build your own electric longboard the heart of the system consists of a so-called brushless DC motor and an ESC AKA in electric speed controller such setups can also be found when you want to build a Quadro copter or for example inside your DVD drive or your hard disk so in this video let's find out how those Motors and ECS work together and what you should be aware of if you want to with the project around them let's get started first of all let's have a look at a similar motor type to get a basic understanding of what is going on DC motors like the name implies use direct current in either polarity to create a rotary remve m m but since looking at them from the outside pretty much explains nothing I used my rotary tool with a cutting wheel to firstly open up the back and afterwards remove the front gear in order to take the whole construction apart inside the metal case we can see two permanent magnets with opposing polarity also known as the STA because they stay in place the rotating parts that are removed is called a rotor and consist in this case of five coils that are connected to a commutator which is divided in five equal parts to keep it a bit simpler though I reduced the number of coils and commutator parts to only two in this diagram the last remaining components of this motor are two carbon brushes which connect our DC voltage to the commutator and thus the coils now if I apply a voltage current starts flowing through them which creates an opposing magnetic fields since they're connected in serious and have a reverse winding Direction the results are then obvious the same magnetic polarity creates a force that push the coils away while the other side of the ster attracts them but just before reaching their final position the carbon brushes reach the other half of the commutator and reverse the magnetic polarity of the coils which get pushed away again and then again and so on and just like that the rotation is created brushless motors use a similar principle but on the other hand change a couple of things around to make it more appealing for certain applications again let's firstly have a look inside this Beast motor in order to find out how it functions this time the rotor consists of four permanent magnets with alternating opposing polarities and this data consist of 12 coils which utilize the metal case as a heat sink to improve the lifespan but to keep it simple once again let's use one magnet with six coils coils in this diagram the three coil pairs which are also connected in serious and with a reverse winding direction are bond together through a star connection which is not a surprise because the label of my motor already said so now we need to energize two coil pairs one after the other in these six steps to create a complete rotation of the rotor while the DC motor used the mechanical principle of a commutator to create rotating Fields the brushless motor uses an electrical one also called the ESC you can get different variations with for example software to program them and all kinds of different features but in the end they all do the same minimum by applying a control voltage to the input aka the yellow wire I can set two reference points which are basically just different length of a voltage burst in order to adjust the frequency in which is six steps for one complete rotation repeats obviously a higher frequency means less time for one rotation and thus a higher RPM the three states of the outputs are high low and floating which is realized through an array of P Channel and N Channel Mass fets the number of parallel mass fets for one outputs in this case six of them directly determines how much current your driver can handle more of them means more current and thus your motor can be more powerful but the price also increases and the overall current draw is also determined by the load which is attached to the shaft the amount of voltage applied to the es and also regulated by a pools with modulation of the different output States okay getting back to the Practical example if I set a constant frequency of around 65 Hertz I can use my tachometer to measure an RPM of around 1,740 if I divide that by 60 I get a frequency of only half the original one but why the reason is the double number of coils and especially the permanent magnets which cause a lower RPM but on the other hand a bigger torque that is also the reason why OutRunner brushless motors are preferred when high torsional moments are necessary due to more space on the outside they simply can accommodate a higher amount of magnets and thus like I already said they can achieve a lower RPM and a higher toque at the same frequency at the end let's talk about the KV rating which stands for RPM per volt applied let's use a 7.4 and 11.1 volt battery as an example with the 520 KV motor I reached a maximum RPM of 3,750 and 5,644 while with the 920 kv1 I reached a maximum of 6,780 and 10,500 so it is true that with a higher KV rating you get more RPM and by calculating with the ratings we get values which are definitely close enough to reality but in the end it's not mainly about the voltage which determines the rotation speed it's about a higher frequency of the ESC that can be achieved with a higher voltage and depends on the characteristic properties of the motor and with that being said you already know quite a bit about brushless motors and the ESC if you like this video don't forget to give it a thumbs up consider supporting me through my patreon campaign in order to keep such videos coming stay creative and I will see you next timein a previous project I showed you how to build your own electric longboard the heart of the system consists of a so-called brushless DC motor and an ESC AKA in electric speed controller such setups can also be found when you want to build a Quadro copter or for example inside your DVD drive or your hard disk so in this video let's find out how those Motors and ECS work together and what you should be aware of if you want to with the project around them let's get started first of all let's have a look at a similar motor type to get a basic understanding of what is going on DC motors like the name implies use direct current in either polarity to create a rotary remve m m but since looking at them from the outside pretty much explains nothing I used my rotary tool with a cutting wheel to firstly open up the back and afterwards remove the front gear in order to take the whole construction apart inside the metal case we can see two permanent magnets with opposing polarity also known as the STA because they stay in place the rotating parts that are removed is called a rotor and consist in this case of five coils that are connected to a commutator which is divided in five equal parts to keep it a bit simpler though I reduced the number of coils and commutator parts to only two in this diagram the last remaining components of this motor are two carbon brushes which connect our DC voltage to the commutator and thus the coils now if I apply a voltage current starts flowing through them which creates an opposing magnetic fields since they're connected in serious and have a reverse winding Direction the results are then obvious the same magnetic polarity creates a force that push the coils away while the other side of the ster attracts them but just before reaching their final position the carbon brushes reach the other half of the commutator and reverse the magnetic polarity of the coils which get pushed away again and then again and so on and just like that the rotation is created brushless motors use a similar principle but on the other hand change a couple of things around to make it more appealing for certain applications again let's firstly have a look inside this Beast motor in order to find out how it functions this time the rotor consists of four permanent magnets with alternating opposing polarities and this data consist of 12 coils which utilize the metal case as a heat sink to improve the lifespan but to keep it simple once again let's use one magnet with six coils coils in this diagram the three coil pairs which are also connected in serious and with a reverse winding direction are bond together through a star connection which is not a surprise because the label of my motor already said so now we need to energize two coil pairs one after the other in these six steps to create a complete rotation of the rotor while the DC motor used the mechanical principle of a commutator to create rotating Fields the brushless motor uses an electrical one also called the ESC you can get different variations with for example software to program them and all kinds of different features but in the end they all do the same minimum by applying a control voltage to the input aka the yellow wire I can set two reference points which are basically just different length of a voltage burst in order to adjust the frequency in which is six steps for one complete rotation repeats obviously a higher frequency means less time for one rotation and thus a higher RPM the three states of the outputs are high low and floating which is realized through an array of P Channel and N Channel Mass fets the number of parallel mass fets for one outputs in this case six of them directly determines how much current your driver can handle more of them means more current and thus your motor can be more powerful but the price also increases and the overall current draw is also determined by the load which is attached to the shaft the amount of voltage applied to the es and also regulated by a pools with modulation of the different output States okay getting back to the Practical example if I set a constant frequency of around 65 Hertz I can use my tachometer to measure an RPM of around 1,740 if I divide that by 60 I get a frequency of only half the original one but why the reason is the double number of coils and especially the permanent magnets which cause a lower RPM but on the other hand a bigger torque that is also the reason why OutRunner brushless motors are preferred when high torsional moments are necessary due to more space on the outside they simply can accommodate a higher amount of magnets and thus like I already said they can achieve a lower RPM and a higher toque at the same frequency at the end let's talk about the KV rating which stands for RPM per volt applied let's use a 7.4 and 11.1 volt battery as an example with the 520 KV motor I reached a maximum RPM of 3,750 and 5,644 while with the 920 kv1 I reached a maximum of 6,780 and 10,500 so it is true that with a higher KV rating you get more RPM and by calculating with the ratings we get values which are definitely close enough to reality but in the end it's not mainly about the voltage which determines the rotation speed it's about a higher frequency of the ESC that can be achieved with a higher voltage and depends on the characteristic properties of the motor and with that being said you already know quite a bit about brushless motors and the ESC if you like this video don't forget to give it a thumbs up consider supporting me through my patreon campaign in order to keep such videos coming stay creative and I will see you next time