First, there is the principle of brush motor
to clarify this issue, we should look roughly brushed motor works. Next, using a three-electrode, the two poles of the rotor as a demonstration brushed motor.
Second, the principle of the brushless motor
First, the brushless DC motor is not, although the model is a DC battery, but after passing through the brushless ESC is transformed to three-phase alternating current to the three on the polarity. It can be seen by the following diagram, the brushless motor is not carbon brush, and a brush contrary, the brushless motor rotor magnets would be ~
three, named brushless motor
relative brush motors, brushless motors named lot better understood , which generally consists of four numbers, for example 2040 brushless motor. This figure represents only the motor dimensions, 2040 represents the diameter of 20mm, a length of 40mm motor. Similarly brushless motor 3650 indicates a motor diameter 36mm, length 50mm.
In fact, the size of 370 brush motor and brushless motors as 2530, size 540 motors and brushless motors as 3650.
Fourth, the characteristics of the brushless motor
1, no carbon brushes, in theory, the rotor and the outside world without having to have a link on the conductor.
2, during operation, the rotational speed of the brushless motor is determined by the frequency of alternating current, the higher the frequency of the brushless motor can be transferred faster.
3, brushless motor speed KV is in strict accordance with the set value, 1000KV represent each Ford Motor speed 1000 rpm accelerate. The voltage is 5V, 1000kv brushless motor speed 5000rpm.
4, during operation, the same speed of the motor torque is adjusted by the strength of the electrical current output of the decision, the greater the greater the current torque. (Ideally, we "smart" Brushless ESC will continue to "monitor" whether we need greater torque of the motor, but also to ensure that no excess torque, in order to avoid waste of expression)
Fifth, the outer rotor and the inner rotor brushless motor
The above principle of the brushless motor shown in FIG inner rotor brushless motor is, as the name implies, the magnet inside. The outer rotor of the brushless motor, in contrast, the magnet "package" on the outside, and A, B, C inside the electrode, this design allows the motor torque is larger, but the speed has come up. In the model, KV value of the outer rotor brushless motor is generally less than 2000, while the inner rotor brushless motor may be to 8000-9000kv. For this reason, the general common external rotor aircraft brushless motor, while model cars and model boats normally used for inner-rotor brushless motor.
Sixth, and felt no sense of brushless brushless
To illustrate this problem we must first understand what sense is the sense of ~, felt a sense of brushless means "Hall sensor", then what is the "Hall" mean? Hall refers to the Hall effect, this phenomenon is the American physicist Hall (AHHall, 1855-1938) in 1879 found that when conducting research institutions metal. When the external magnetic field perpendicular to the current through the conductor, the conductors between the two end faces of the magnetic field perpendicular to the current direction and a potential difference occurs, the Hall effect is the phenomenon. The potential difference is also called the Hall potential difference.
So why do we sense this stuff? This problem must say clear sense of a brushless drawback of never talking about. Just said brushless motor speed is determined by the frequency of the alternating current, then ESC to find ways to understand the current motor speed and the current state of the motor. In fact, this has been very easy for the normal operation of the motor is, but for a start-up or run very slowly, it becomes more of a motor trouble (is difficult to accurately measure than the state motor speed), so no sense without brush motor will not even be linear tremble at low speeds, while the torque is also difficult to start stronger than the same grade brush motor.
But it was discovered that no matter what the operating state of the brushless motor, it's the Hall effect is obvious, so by the Hall effect power transfer can easily know whether high speed or low-speed operation of the motor, so as to solve without a sense of brushless motor problems! But for now, the Hall sensor is not a bargain, it felt brushless motor, ESC prices than no sense of brushless lot more expensive.
Seven common model with a brush, brushless no sense, felt contrast brushless motor
brush motor brushless felt no sense of brushless
Conversion efficiency: low high
motor output power: low high
starting torque: Good general good
high-speed torque: general good
low-speed linear: good general good
in high speed linear: Ok
maximum speed (usually 540 motor): Common 20,000 common 50,000 50,000 common
easy to wear: easy to wear easy to wear easy to wear
motor price (540) mid-range minimum 120RMB 100RMB 200RMB lowest
electricity price adjustment (540) mid-range average about 120 lowest minimum 200RMB 300RMB
works brushless motor detailed interpretation
Share article on the works of some of the brushless motor knowledge, to ensure that as long as there is a physical knowledge of high friends will be able to able to understand, I hope interested friends down to see the patient, learn from each other! first of all for everyone to review some of the basic set : the left-hand, right-hand rule, the right-hand screw rule. Do not ignorant force, I will explain below. Left-hand rule, which is the basis of the motor rotation stress analysis, is simply the current carrying conductor in a magnetic field, a force will be.
Let magnetic field lines pass through the front of the palm, fingers direction as the current direction, the direction of the thumb direction to generate a magnetic force, I believe that people like to play there is a certain model of the physical basis of ha ha. Right-hand rule, which is generated based on the induced electromotive force, with the left-hand opposite to the magnetic field generates an electromotive force in a conductor is pulled by the cutting force of magnetic field lines.
So that magnetic field lines pass through the palm, thumb direction is the direction of movement, the direction of the finger emf generated. Why talk about it induced electromotive force? I do not know there is no similar experience, put together a three-phase line of the motor to rotate the electrical resistance is very great opportunity to discover the hand, this is because the rotation of the motor produces induced process electromotive force, thereby generating electric current, a magnetic field will produce a current flow through the conductor and a rotational direction opposite to the force, it will feel a great resistance to rotation. I do not believe you can try.
Separate three-phase line, the motor can be easily rotated
three phase lines merge, the motor rotation resistance is extremely large right-hand screw, with a right hand holding the solenoid is energized, so that four fingers curved line with the current direction, then the meaning of that end of the thumb N-pole coil is energized.
This is the basis of a given polarity of energization of the coil is determined, the direction of the red arrow is the direction of the current. After reading the three is set, we are going to look at the basic principle of rotation of the motor. Part I: DC model of physics we find the model of a DC motor through high school, to be analyzed by a simple magnetic circuit analysis.
Current, in accordance with right-handed screw rule, will generate additional magnetic induction B (such as a thick arrow as shown) direction to right the state 1 when the two coils through, the middle rotor will try to make their own internal magnetic induction line direction consistent with magnetic induction lines outside direction to form a magnetic line closed loop shortest, so that the inner rotor will be rotated clockwise. When the rotor magnetic field direction perpendicular to the direction of the external magnetic field, the rotor rotating torque maximum suffered. Note here that the "moment" the biggest, not "force" the greatest. Indeed, when the external magnetic field is consistent with the direction of the magnetic field of the rotor, rotor magnetic suffered the maximum, but this time the rotor is horizontal, arm of 0, of course, will not be rotated. He adds that moment is the product of force and moment arm. Wherein a is zero, the product is zero. When the rotor is rotated to the horizontal position, although not subjected to rotational torque, but because of reasons of inertia, will continue to rotate clockwise, changing the current time if the two directions of the solenoid, as shown below, the rotor will continue clockwise rotation forward,
2 thus changing the state of two solenoid current direction, the rotor will turn up continuously. This action changes the direction of the current, called commutation. Added: commutation only when the position of the rotor, whereas no direct relationship with any other amount. Second part: three-phase two-pole rotor machine in general, the three-phase windings of the stator has a star connection mode and triangle mode coupling, and the "two-two-phase star-connected conduction mode" is most commonly used, it is used here the model used to make a simple analysis.
The figure shows the coupling of the stator windings (not shown rotor is a dipole magnet phantom), connected by three windings are coupled together point to the center of a "Y" fashion. Motor can lead the entire three lines A, B, C. Twenty-two therebetween when energized, 6 cases, respectively, AB, AC, BC, BA, CA, CB noted that this is in order. The first stage I see the following: AB phase energized
when the AB phase is energized, the magnetic induction coil electrode lines A generated in the direction as shown by arrow red, B pole magnetic field lines generated by the blue arrow direction as shown, then the resulting force is the green direction indicated by arrow, then it is assumed which has a two-pole magnet, according to the "intermediate rotor will try to make the direction of the magnetic induction lines consistent with their own internal outer magnetic induction line direction" is the direction of N-pole and will green coincides with direction of the arrow. As for C, being what he did not do. The second stage: AC phase on
the third stage: BC-phase power
Phase III: BA-phase power
in order to save space, we will not describe one by one CACB model, and so we can own it. The following intermediate magnet (rotor) FIG state:
every 60 degrees of rotation of the rotor
six to complete the full course of rotation, wherein the commutation Part 6: multi-phase windings of the multi-pole rotor machine we will look at a complex points, view (a) is a three-phase six-pole winding nine (three pairs of poles) of the inner rotor motor, its winding connection method shown in Figure (b). Visible, which is also connected to three-phase windings from view (b) together at an intermediate point, they are also star-connected mode. In general, the number of windings of the motor are permanent magnet poles and the number is inconsistent (for example, 6 poles with windings 9, instead of six-pole winding 6), this is to prevent the rotor magnets and stator teeth align attraction.
Its movement principle is: N pole and the conduction winding S poles of the rotor have aligned movement trend, while the S pole of the rotor and the N pole with a conduction winding alignment movement trend. S and N is the mutual attraction, attention prior to analysis with a certain distinction. Well, then still help us analyze it, the first stage: AB phase on
the second stage: AC phase on
the third stage: BC phase on
the fourth stage: BA energized
Phase V: CA energized
sixth stage: CB energized
more than six different energized state, wherein rotation of five experienced. Each process is 20 degrees.
Part IV: reading the external rotor brushless DC motor brushless DC motor rotor structure inside, we look at the outer rotor. The difference is that the original outer rotor motor in the center position of the magnet made of one piece, attached to the housing, the motor is running, the entire housing is in turn, while the middle of the stator coil does not move. Than the outer rotor brushless DC motor, the moment of inertia of the rotor is much larger (since the mass of the rotor are mainly concentrated in the shell), the motor speed is slower than the inner rotor, the KV value is typically hundreds to thousands between. HM is the main use of brushless motors winded way about it. KV brushless motor is defined as: the speed / V, meaning increased by 1 volt input voltage, increasing the idle speed of the brushless motor rotational speed value. For example, a nominal value of the outer rotor brushless motor 1000KV, at a voltage of 11 volts conditions, that is, the maximum no-load speed: 11,000 rpm (rpm meanings are: revolutions / min). Series with the same dimensions of the brushless motor, according to the number of winding turns, KV will exhibit different characteristics. Number of turns of the winding, KV value, the highest output current is small, a large torque; small number of turns, the high KV values, maximum output current, small torque. I previously tested the limits current flow through the motor 2204, the single motor can Biao 25A, 15A and 2212 series motors are not on. Brushless DC motor of the outer rotor
Analysis methods and the inner rotor motor Similarly, you can own analysis, based on the N right-handed screw Theorem determination coil / S pole, N pole and the stator windings of a permanent magnet rotor S pole with alignment (suction) is trend rotor with permanent magnets the S pole and N pole stator windings have aligned (suction) the tendency to drive the rotation of the motor. Analysis of the structure of the motor 2212 1000kv classic brushless motors.
Pictured DJI 2312S motor and motor XXD 2212 (FIG anatomy) is structured as follows: the stator winding fixed on the base, shaft and the housing together form a rotor, a stator is inserted in the middle of the bearing.
Pictured xxd2212 coil dismantling FIG
graph 12-pole winding 14 (i.e., seven pairs of poles), the motor windings shown in FIG later made about six two-phase energization case, it can be seen, although the number of windings and magnetic poles can have many variations, but the power transfer control point of view, it really energized the order is the same, that is to say, regardless of the outer rotor or inner rotor motor, follow AB-> AC-> BC-> BA-> CA-> CB the commutation sequence energized. Of course, if you want, then reversing the motor, an electronic order is pinned over power; physical methods directly swap any two lines, A and B are reversed is assumed, then the order is BA-> BC-> AC-> AB- > CB-> CA, we have not found where the order is completely upside down.
AB energized phase
AC phase energization
BC phase energization
BA phase energization
CA phase energization
CB-phase power
to explain that, since each of the lead wires simultaneously accessing two windings, so there are two routes to go current. In order to simplify this problem as much as possible, the following figures drawn only along the main current direction, there is one current, not shown, the other circuit current situation is analyzed on the back, to the commutation circuit for detecting the position of .
