Motopreserve
Drone Enthusiast
Quick Back-story: I was in the planning stages of my last build - a hexa mid-lifter, and had settled on the SunnySky 3508-20 580kv motor, coupled with some RTF tweaked SimonK flashed Ice-Blue series 2-6S Opto ESCs with the filtering removed for "pancake" motors. I had a panic moment after seeing mention of SimonK not working well with "high-Pole count" or pancake motors. Since the SS motors were listed on several sites as having 28 poles, I scrambled to find an appropriate ESC that would work well with the motors. Turned out that the SS motors were mislabeled, and all my worry and extra expenditure was for naught. The 3508-20 were in fact 14 pole, and this misinformation had been provided by the manufacturer....
Frustrated with the lack of information, and worse, MIS-information, I decided to clear a few things up in my own mind, and hopefully help a few of you who have had similar questions. No better people to ask than the folks over at KDE Direct, and Chris was kind enough to answer the questions I had. The following is the list of questions I sent him, and if we are lucky, we can continue this 'line of questioning' in the future...
Chris' answers begin below:
Let’s start off with the differences between a “High-Pole” to “Low-Pole” count motor. The industry has loosely created a standard of 8 to 14 magnet-poles being the traditional design of magnets in a motor. Now, with motors being produced with more than 14 magnets, the industry is calling these “High-Pole” count motors. Remember this is a loose “Hobby Standard”, as there is no real industry standard that would define this.
Let’s go over the motor to be more clear about pole counts. There is usually only one type of pole count that a manufacturer is listing for a motor. This is the number of magnets in a motor, and they are permanently bonded to the internal perimeter of the magnet bell. An example would be the KDE4014XF-380 motor, it’s a 18S24P motor as stated here under the general information about the motor: http://kdedirect.com/<wbr>KDE4014XF380.html. In this regard, the motor has 18 stator-slots with 24 magnet-poles. Compare this to the KDEXF2814-775 motor with 12S14P, equaling 12 stator-slots and 14 magnet-poles. The stator “slots” or “teeth” are NOT considered a pole. The industry has been making the 12 stator-slot, 14 magnet-pole motor as more of a standard for a years, and are common in the RC Airplane and Helicopter arena as well. This has been the basis for what is considered low-pole and high-pole count motors. This does not mean it’s a standard, it’s just the way the hobby industry has taken it. To figure out the pole-count, you simply count the magnets.
The industry is evolving in a way that higher pole-count motors are becoming more common. ESC manufacturers have traditionally been designing their firmware to run the current industry “standard” for pole-counts. This “Hobby Standard” has been based around 14 pole-count motors and the ability to drive motors with higher Kv ratings (up to the limit of electrical-RPM). As the magnet-pole counts increase, it’s harder for an ESC processor to drive or keep the motor synchronous. You need a processor that is capable of handling the higher pole motors, to keep them performing and respond near-instantaneous to the flight-controller demands. (My next question will be what does the ESC need to "handle the higher pole motors?").
Pancake motors are just a version of a basic motor. They have been around for many years in other types of industries, the hobby industry has just started labeling the flatter motors “Pancake motors”. This really has to do with a motor width being larger then it’s height, making it look like a "pancake." There are advantages to “Pancake Motors”, both in efficiency, torque-generation, and cooling. It’s much easier to blow air through an open Pancake motor then a more traditional-style motor.
This is an evolution of components, as all new technology goes through this. We have seen this on the RC helicopter side for the last 10 years. All the power systems were small and designed around lower-voltage batteries and power-systems. If you have been involved in the electric RC helicopters world, you have seen the batteries changing in size/voltage for a long time. The general progression has been for the system continually going up in voltage for efficiency, while keeping all electronics running at lower temperatures and capability of generating greater power. This is now carrying over to the multi-rotor side of the industry and there are advantages to be had with the additional options for motor design. The key difference in multi-rotors is the motors are not coupled to a transmission, they are direct drive - changing the way they’re designed for performance and allowing for different electromagnetic designs to be used to push the limits of efficiency and thrust.
I will be following up with some additional question and clarifications, and if Chris is patient enough - it looks like we could have a really informative thread on our hands. I would like to thank Chris (and the rest of the folks at KDE) for taking the time to answer my basic questions...
Frustrated with the lack of information, and worse, MIS-information, I decided to clear a few things up in my own mind, and hopefully help a few of you who have had similar questions. No better people to ask than the folks over at KDE Direct, and Chris was kind enough to answer the questions I had. The following is the list of questions I sent him, and if we are lucky, we can continue this 'line of questioning' in the future...
- What is considered high-pole count? What is considered low-pole count (or traditional) for brushless motors?
- When people talk about pole count, are they talking about stator poles or magnet poles?
- When trying to count poles, what are stator poles and what are magnet poles (or magnet pairs)? Does this design aspect vary by manufacturer?
Chris' answers begin below:
Let’s start off with the differences between a “High-Pole” to “Low-Pole” count motor. The industry has loosely created a standard of 8 to 14 magnet-poles being the traditional design of magnets in a motor. Now, with motors being produced with more than 14 magnets, the industry is calling these “High-Pole” count motors. Remember this is a loose “Hobby Standard”, as there is no real industry standard that would define this.
Let’s go over the motor to be more clear about pole counts. There is usually only one type of pole count that a manufacturer is listing for a motor. This is the number of magnets in a motor, and they are permanently bonded to the internal perimeter of the magnet bell. An example would be the KDE4014XF-380 motor, it’s a 18S24P motor as stated here under the general information about the motor: http://kdedirect.com/<wbr>KDE4014XF380.html. In this regard, the motor has 18 stator-slots with 24 magnet-poles. Compare this to the KDEXF2814-775 motor with 12S14P, equaling 12 stator-slots and 14 magnet-poles. The stator “slots” or “teeth” are NOT considered a pole. The industry has been making the 12 stator-slot, 14 magnet-pole motor as more of a standard for a years, and are common in the RC Airplane and Helicopter arena as well. This has been the basis for what is considered low-pole and high-pole count motors. This does not mean it’s a standard, it’s just the way the hobby industry has taken it. To figure out the pole-count, you simply count the magnets.
The industry is evolving in a way that higher pole-count motors are becoming more common. ESC manufacturers have traditionally been designing their firmware to run the current industry “standard” for pole-counts. This “Hobby Standard” has been based around 14 pole-count motors and the ability to drive motors with higher Kv ratings (up to the limit of electrical-RPM). As the magnet-pole counts increase, it’s harder for an ESC processor to drive or keep the motor synchronous. You need a processor that is capable of handling the higher pole motors, to keep them performing and respond near-instantaneous to the flight-controller demands. (My next question will be what does the ESC need to "handle the higher pole motors?").
Pancake motors are just a version of a basic motor. They have been around for many years in other types of industries, the hobby industry has just started labeling the flatter motors “Pancake motors”. This really has to do with a motor width being larger then it’s height, making it look like a "pancake." There are advantages to “Pancake Motors”, both in efficiency, torque-generation, and cooling. It’s much easier to blow air through an open Pancake motor then a more traditional-style motor.
This is an evolution of components, as all new technology goes through this. We have seen this on the RC helicopter side for the last 10 years. All the power systems were small and designed around lower-voltage batteries and power-systems. If you have been involved in the electric RC helicopters world, you have seen the batteries changing in size/voltage for a long time. The general progression has been for the system continually going up in voltage for efficiency, while keeping all electronics running at lower temperatures and capability of generating greater power. This is now carrying over to the multi-rotor side of the industry and there are advantages to be had with the additional options for motor design. The key difference in multi-rotors is the motors are not coupled to a transmission, they are direct drive - changing the way they’re designed for performance and allowing for different electromagnetic designs to be used to push the limits of efficiency and thrust.
I will be following up with some additional question and clarifications, and if Chris is patient enough - it looks like we could have a really informative thread on our hands. I would like to thank Chris (and the rest of the folks at KDE) for taking the time to answer my basic questions...