Experience in the use of brushes, inductive and brushless motors

First, the principle of brush motor
To clarify the problem, you should have a rough idea of how the brush motor works. Next, a three-electrode, two-pole internal rotor brush motor is used as a demonstration.

Two, brushless motor working principle

First, the brushless motor is not a DC motor, although the model is powered by a DC battery, but after a brushless ESC, the transition is transferred to the three-phase alternating current to three polarities. As can be seen from the following figure, brushless motor is not a carbon brush, and brush the opposite, brushless motor magnet into the rotor ~

Third, the name of brushless motor

Relative brush motor, brushless motor name good understanding a lot, generally it consists of four numbers, such as 2040 brushless motor. This number represents the overall size of the motor, and 2040 indicates a motor with a diameter of 20mm and a length of 40mm. Similarly 3650 brushless motor indicates the diameter of this motor 36mm, length 50mm.

In fact, 370 brush motor size and 2530 brushless motor, 540 motor size and 3650 brushless motor.

Four, the characteristics of brushless motor

1, there is no carbon brush, theoretically the rotor does not need to have a conductor on the outside of the link.

2, in the process of operation, the speed of the brushless motor depends on the frequency of alternating current, so the higher the frequency of brushless motor can turn faster.

3, brushless motor speed is strictly set according to the KV value, 1000KV means that each Ford Motor speed 1000 rpm. So when the voltage is 5V, the 1000kv brushless motor speed 5000rpm.

4, in the operation process, the same speed motor torque is determined by the current intensity of the output of the ESC, the larger the current torque greater. (Ideally, our "smart" brushless ESC will constantly "monitor" whether our motors need more torque, but also ensure that the torque is not excessive, so as not to waste expression)

Five, external rotor and internal rotor brushless motor

The above brushless motor working principle is shown in the internal rotor brushless motor, as the name implies, the magnet inside. The outer rotor brushless motor is instead, its magnet "bag" is outside. And a, B, C electrodes in the inside. This design can make the motor more torque, but the speed is not up. In the model, the general external rotor brushless motor KV value within 2000, and the internal rotor brushless motor can be to 8000-9000kv. For this reason, general aircraft on the common external rotor brushless motor, and model cars and model ships generally use the internal rotor brushless motor.

Six, feeling brushless and no sense brushless

To illustrate this problem first of all to understand the sense of what is the sense of the feeling is not in the brush refers to the "Hall sensor", then what is "Hall" it. Hall refers to the Hall effect, which was discovered by US physicist Hall (a.h.hall,1855-1938) in 1879 when studying the conductive mechanism of metals. The Hall effect occurs when the current is perpendicular to the outer magnetic field through the conductor, and the potential difference is present between the two end faces perpendicular to the magnetic field and the current direction of the conductor. This potential difference is also called Hall potential difference.

So why are we sensing this thing? To clarify this problem, we must start with a shortcoming of the no-sense brushless. Just said that the speed of the brushless motor depends on the frequency of alternating current, then the ESC to find ways to understand the current speed of the motor and motor status. In fact, this is a normal operation of the motor is very easy, but for a just starting or running speed is very slow motor is more troublesome (it is difficult to measure the state of the motor speed accurately), so no sense brushless motor will be at low speed linear bad even may tremble, and the starting torque is also difficult to stronger than the same level brush motor.

However, it is found that no matter what the operating state of the brushless motor, its Hall effect is obvious, so through the Hall effect ESC can easily know whether high-speed or low-speed motor running state, so as to solve the problem of brushless motor. But at present, the hall sensor is not cheap goods, so the feeling of brushless motor, ESC price will be more expensive than no sense brushless.

Seven, the common model with brush, no sense brushless, inductive brushless motor comparison

Brushless motor without feeling brushless

Conversion efficiency: Low high

Motor output power: Low high

Starting torque: Good general good

Medium and High speed torque: generally good

Low-speed linearity: better general good

Medium-High speed linearity: Okay, good.

Maximum speed (general 540 motor): Common 20,000 common 50,000 common 50,000

Easy wear and tear: easy to wear and abrasion resistant

Motor Price (level 540) mid-range 100RMB min 120RMB minimum 200RMB

ESC Price (Level 540) mid-range Average 120 min. 200RMB Minimum 300RMB