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Compared with the brushed motor, the brushless motor cancels the carbon brush structure, so the brushless motor needs a component that can replace the function of the carbon brush, which is the ESC.
The full name of ESC is electronic speed controller (ESC for short), and ESC corresponds to different types of motors, which are divided into brushless ESC and brushed ESC. There is no need for ESC when the brushed motor is rotating, but if there is no ESC, the speed of the motor cannot be controlled. The brushless motor must have an ESC, otherwise it cannot rotate.
ESC function
The ESC can convert the input DC power into three-phase AC power to power the motor, and control the voltage and current of the motor according to the control signal sent by the flight controller, so as to drive the motor to achieve the required speed output. The ESC functions as a voltage changer, which converts the battery voltage for the receiver and the flight control board to work. When the motor is running, the current is very large. When the motor is working normally, if there is no ESC, the flight control board cannot bear such a large current.
ESC connection
The connection of the brushless ESC is shown in the figure below: the input line is connected to the battery, the signal line input line is connected to the receiver, and the three signal output lines (two with brushes) are connected to the motor.
The ESC generally has a power output function, that is, there is a voltage output of about 5V between the positive and negative poles of the signal line, which supplies power to the receiver through the signal line, and the receiver supplies power to the steering gear and other control equipment.
ESC parameter A
The most common parameter A of the ESC refers to the amount of current that the ESC can stably adjust the output. For example, a 30A ESC can stably output a maximum current of 30A. If it is used beyond the standard, it will cause the ESC to burn out.
Selection relationship of motor, battery and ESC
First of all, you need to know the logical relationship: determine the motor -> determine the ESC -> finally determine the battery. Don't ignore the condition of the motor, blindly choose the battery, ESC, it is easy to burn the motor.
Select instance:
For example, choose a brushless motor with a maximum power current of 30A. And the battery we can determine from the capacity and rate of the battery. For example, for a battery whose parameters are 2200mah 10C, its maximum discharge current is (2200mh=2.2A) 2.2A*10=22A, which is obviously not enough.
If it is a 2200mah 20C battery it will do. Because the maximum discharge current of the battery is 44A, and the maximum (consumption) of the motor is 30A, which is equivalent to a large horse-drawn cart, the battery discharge will be easier, and the motor can run at full power, so the power obtained will be sufficient.
Therefore, with a 2200MA 20C battery, a motor with a maximum load current of 30A, and an ESC with a maximum output of 45A is a reasonable configuration.
Note that
if we choose batteries for the four-axis, because the four-axis has four sets of ESCs, if a 20A ESC is used, then we need to use 20A X 4 = 100A batteries. We generally use 5000MA for four-axis aerial photography. A 20C battery is 5 X 20C = 100A, which has reached the optimal weight and capacity matching relationship. The four-axis has multiple motors, so a larger battery should be selected.
The difference between 3 signal wires and 2 signal wires of ESC
The three wires are with BEC output, that is to say, the ESC with three wires can
provide 5V power supply to the receiver. The two are only the signal line and GND. The three-wire
one has an extra 5-voltage output line, which means that it can be used as an output power supply, and the two-
wire one does not have it, only the ground wire and the input signal wire. One is with 5V output
and the other is without 5V output, it doesn't matter.