Brushless Motor
Structure, brushless motor and brush motor have similarities, but also the rotor and stator, but the structure and the brush motor is the opposite; brush motor rotor is the coil winding, and the power output shaft connected to the stator is permanent magnetism Steel; brushless motor rotor is a permanent magnet magnet, together with the shell and output shaft connected to the stator is the winding coil, remove the brush motor used to alternately change the electromagnetic field of the brush, so called brushless motor ( Brushless motor), it is now a problem, there is no electromagnetic field transformation, how to brushless motor rotation?
Operating principle
In simple terms, by changing the alternating current frequency and waveform of the current wave input to the brushless motor stator coil, a magnetic field around the geometrical axis of the motor is formed around the winding coil, which rotates the permanent magnet magnet on the rotor, The motor will turn up, the performance of the motor and the number of magnetic steel, magnetic flux strength, the motor input voltage and other factors, but also with the brushless motor control performance has a great relationship, because the input is DC, the current needs of electronic The governor turns it into a 3-phase alternating current, and it also needs to receive the control signal from the remote receiver to control the speed of the motor to meet the needs of the model. In general, the structure of the brushless motor is relatively simple, and really determine its performance or brushless electronic governor, a good electronic governor requires a single-chip control program design, circuit design, complex processing technology Of the overall control, so the price is much higher than the brush motor.
Comparison
Brush motor shortcomings
1, large friction, loss of large
Old die friends in the past when playing brush motor problems are encountered, that is, after a period of time using the motor, you need to open the motor to clean the motor carbon brush, time and effort, maintenance strength as much as a family cleaning.
2, fever, short life
As the structure of the brush motor, brush and commutator contact resistance is large, resulting in a larger overall resistance of the motor, easy to heat, and permanent magnet is a thermal element, if the temperature is too high, then the magnet is demagnetized , So that motor performance, affecting the life of brush motor.
3, low efficiency, low output power
The above mentioned brush motor heating problem, largely because the current work done in the internal resistance of the motor, so the power is converted to a large degree of heat, so the brush motor output power is not large, the efficiency is not high.
Brushless motor advantages
1, no brush, low interference
Brushless motor to remove the brush, the most direct change is that there is no brush motor running when the spark, which greatly reduces the spark on the remote control radio interference.
2, low noise, smooth operation
Brushless motor without brush, running friction greatly reduced, running smoothly, the noise will be much lower, this advantage for the model running stability is a huge support.
3, long life, low maintenance costs
Less brush, brushless motor wear is mainly on the bearing, from the mechanical point of view, brushless motor is almost a maintenance-free motor, and when necessary, just do some dust maintenance can be. Up and down a comparison, you know the brushless motor relative to the advantages of brush motor where, but everything is not absolute, brush motor low-speed torque performance, torque and other performance characteristics are irreplaceable brushless motor, but With regard to the ease of use of the brushless motor, with the development trend of the brushless controller and the development of brushless technology at home and abroad with the market competition, brushless power system is in the high-speed development and popularization stage, which also greatly promoted The development of model movement.
Specific difference
1, the scope of application:
Brushless motor: usually used in the control requirements are relatively high, the speed is relatively high equipment, such as aircraft model, precision instruments and other motor speed control strictly, the speed reaches a high device.
Brush motor: usually power equipment are used brush motor, such as hair dryer, factory motor, home range hood, etc., in addition to the motor speed can reach a very high, but because of the carbon brush wear, use Life is better than brushless motor.
2, the service life:
Brushless motor: usually life in the tens of thousands of hours this order of magnitude, but because of the different brushless motor bearing life is also very different.
Brush motor: brush motor is usually a continuous working life of several hundred to one thousand hours, to reach the use of the limit you need to replace the carbon brush, or is likely to cause bearing wear.
3, the use of results:
Brushless motor: usually digital frequency control, controllable strong, from a few minutes per minute, to tens of thousands of minutes per minute can be easily achieved.
Brush motor: the old carbon brush motor after the general start of the work of constant speed, speed is not very easy, series motor can also reach 20,000 rpm,
But the service life will be shorter.
4, energy-saving aspects:
Relatively speaking, the brushless motor using frequency control technology will be much more energy than the string motor, the most typical is the inverter air conditioner and refrigerator.
5, the future maintenance, the carbon brush motor need to replace the carbon brush, if the replacement will not cause the motor damage, and brushless motor, long life, usually brush motor more than 10 times, but the need to replace the bad Motor, but routine maintenance is basically not needed.
6, noise and whether it is brush motor has nothing to do, mainly to see the bearing and the internal components of the motor with the situation.
7, the model brushless motor parameters, in addition to dimensions (diameter, length, shaft diameter, etc.), weight, voltage range, no-load current, maximum current and other parameters, but also an important indicator - KV value, this The value is a brushless motor unique performance parameters, is to judge the performance characteristics of brushless motor is an important data.
KV value definition
Brushless motor KV value is defined as speed / V, meaning the input voltage increases by 1 volt, brushless motor idling speed increases the speed value. From this definition, we can see that the brushless motor voltage input and motor idling speed is to follow a strict linear proportional relationship.
KV value of the meaning
The meaning of the brushless motor is not only that the motor speed and voltage into a strict linear proportional relationship, but also for the performance of the motor has an open expression.
Brushless motor friends have this feeling, with the level (diameter) of the brushless motor, the outer rotor and the internal rotor of the power comparison, will find the outer rotor motor torque larger, to "hard" some, Internal rotor motor torque slightly smaller, to "soft" some, a look at the motor parameters, the outer rotor motor KV value of more than 800, more than 1,000 internal rotor motor to more than 2000. Look at the speed, the speed of the inner rotor motor is significantly higher than the outer rotor motor. In fact, these characteristics are related to the KV value, in accordance with the definition of KV value to explain the brushless motor idling speed, is the KV value multiplied by the input voltage, which also explains the internal rotor motor speed is higher than the outer rotor brushless Motor.
On the torque characteristics of view, KV value of a certain sense of the performance of the motor torque performance, take the outer rotor motor, the motor no-load speed is generally like, but with the load (such as propeller), the speed dropped to no-load speed 60% -70%, but take the same level of the inner rotor motor to test, then the load speed can only be its no-load speed of 30% -40%, which clearly reflects the difference between the two motor torque characteristics, The internal rotor motor with the load capacity is relatively low, in order to meet the torque work, the internal rotor motor must be self-speed reduction, increase the current through the current constant, so the motor output power increased, the inner rotor motor This type of torque is also reflected in the specific application, before a lot of light foam fixed-wing aircraft, the initial use of the internal rotor brushless motor, but because of the torque characteristics of the reason, the aircraft propeller is not directly connected to the motor Direct drive), but to increase a reduction gear set, in order to improve the torque of the inner rotor motor performance.
The same series of brushless motor with dimensions, KV value can also distinguish the characteristics of the motor, such as B3674 rotor motor, a KV value is 1860, a KV value is 2075, that the first motor torque will be larger, the peak Work current is relatively small; the second motor technology is higher, but the torque characteristics than the first motor is worse, the peak current will be larger.
Brushless motor KV meaning, must let you benefit from
Some of the basic knowledge models of brushless motors with low brushless KV values of 1-2 thousand, high to 5-6 thousand, he represents the voltage rise of 1 volt each, the speed increase in the value of the brushless, this The value is constant
For the same size specifications of the brushless: &
Winding turns more, KV value is low, the maximum output current is small, but the torque is large
Winding turns less, KV value is high, the maximum output current, but the torque is small
Alone from the KV value, can not evaluate the motor is good or bad, because different KV values have different applications:
Low voltage environment (7.4v)
KV value is low, due to low speed, suitable for a small reduction ratio and a larger propeller, by a larger load to enhance the current, the output of higher power;
KV value is high, due to the higher speed, suitable for large reduction ratio and smaller propeller, to meet the output power conditions, to reduce the load, to avoid the current is too large;
High voltage environment (11.1v)
KV value is low, in this voltage environment can achieve a higher speed, torque is also good, more ideal. Need to match the larger reduction ratio and smaller propeller, to meet the output power conditions, to reduce the load, to avoid the current is too large;
KV value is high, the speed in the environment is too high, in order to avoid the current is too large, to minimize the load. Using its high speed, for the duct fan engine is very suitable.
7.4v and 11.v are just examples that are commonly used at a small level. Brushless voltage range is very wide, amazing performance.
working principle
Brushless DC motor is the use of semiconductor switching devices to achieve electronic commutation, that is, with electronic switching devices instead of the traditional contact commutator and brush. It has the advantages of high reliability, no change of spark, low mechanical noise, widely used in high-grade recording blocks, video recorders, electronic equipment and automated office equipment.
Brushless DC motor consists of permanent magnet rotor, multi-pole winding stator, position sensor and other components. The position sensor converts the current of the stator winding in a certain order according to the change of the position of the rotor (that is, the position of the rotor pole relative to the stator winding is detected and the position sensing signal is generated at the determined position and processed by the signal conversion circuit To control the power switch circuit, according to a certain logical relationship between the winding current switching). The operating voltage of the stator winding is provided by the electronic switch circuit controlled by the position sensor output.
Position sensors are magnetic, photoelectric and electromagnetic three types.
A brushless DC motor using a magnetically sensitive position sensor is mounted on a stator assembly using a magnetoresistive device (such as a Hall element, a magnetically susceptible diode, a magneto-sensitive transistor, a magnetoresistive resistor, a dedicated integrated circuit, etc.) To detect the permanent magnet, the rotor rotation when the magnetic field changes.
A brushless DC motor using a photoelectric position sensor is provided with a photoelectric sensor at a certain position on the stator assembly. The rotor is provided with a light shielding plate and the light source is a light emitting diode or a small light bulb. Rotor rotation, due to the role of the shading plate, the photosensitive element on the stator will be a certain frequency intermittent pulse signal. The brushless DC motor with electromagnetic position sensor is equipped with electromagnetic sensor components (such as coupling transformer, proximity switch, LC resonant circuit, etc.) on the stator assembly. When the position of the permanent magnet rotor changes, the electromagnetic effect will make the electromagnetic sensor Generates a high frequency modulated signal whose amplitude varies with the rotor position.