Types of motors?
There are two types of motors / motors in multi-rotor machines:
- Brushed (other names: DC) / Coreless.
- Brushless.
Their main difference is that in a collector motor the windings are located on the rotor (rotating part), and in a brushless motor - on the stator. Without going into details, let's say that a brushless motor is preferable to a brushed one because it most satisfies the requirements set before it. Therefore, this article will focus on just this type of motors. More details about the difference between brushless and brushed motors can be found in of this article
Despite the fact that BK motors began to be used relatively recently, the very idea of their device appeared quite a long time ago. However, it was the advent of transistor switches and powerful neodymium magnets that made their commercial use possible.
The device of the BC - motors
The design of the brushless motor consists of a rotor on which magnets are fixed and a stator on which the windings are located. Just by the relative position of these components, BC engines are divided into inrunner and outrunner.
In multi-rotor systems, the Outrunner scheme is more often used, since it allows the highest torque to be obtained.
Pros and cons of BC - engines
Pros:
- Simplified design of the motor due to the exclusion of the collector from it.
- Higher efficiency.
- Good cooling.
- BK engines can run in water! However, do not forget that due to water, rust can form on the mechanical parts of the engine and it will break after some time. To avoid such situations, it is recommended to apply a water-repellent lubricant to the motors.
- Lowest RFI.
Cons:
The only disadvantage is the impossibility of using these motors without ESC (speed controllers). This somewhat complicates the design and makes BC motors more expensive than collector motors. However, if the complexity of the design is a priority parameter, then there are BC motors with built-in speed controllers.
How do I choose motors for my drone?
When choosing brushless motors, first of all, you should pay attention to the following characteristics:
- Maximum current - this characteristic shows what maximum current the motor winding can withstand in a short period of time. If this time is exceeded, then engine failure is inevitable. This parameter also affects the choice of ESC.
- Maximum voltage - as well as maximum current, indicates how much voltage can be applied to the winding for a short period of time.
- KV is the number of engine revolutions per volt. Since this indicator directly depends on the load on the motor shaft, it is indicated for the case when there is no load.
- Resistance - The motor efficiency depends on the resistance. Therefore, the lower the resistance, the better.
