Under normal circumstances, according to the type of working power supply: can be divided into DC motor and AC motor. Dc motors can be divided into brushless dc electric motor and brush DC motors according to their structure and working principle. In a narrow sense: brushless motor refers to a motor without brush and commutator (or collector ring), also known as a commutator motor. In a broad sense: all brushless motors are brushless motors.
As early as the birth of the motor in the 19th century, the practical motor produced is a brushless form, that is, the AC squirrel cage asynchronous motor, which has been widely used. However, asynchronous motors have many insurmountable defects, so that the development of motor technology is slow. The transistor was born in the middle of last century, so the brushless DC motor using transistor commutator circuit instead of brush and commutator came into being. This new brushless motor is called electronically commutated DC motor, which overcomes the shortcomings of the first generation of brushless motors.
Brushless DC motor: Read many articles and classification introductions, brushless DC motor and brushless DC motor in most cases refer to the same term. Included in many articles brushless DC motor and DC brushless motor is also very serious confusion, almost the same existence. Therefore, in a broad sense, brushless DC motor, brushless DC motor, referred to as BLDCM. But from a narrow point of view, brushless DC motor or brushless DC motor refers to a small power direct current motor with electronic commutation, also known as commutator motor, commutator free direct current motor. It is equivalent to a reverse mounted DC motor in structure, its armature is placed on the stator, and the rotor is a permanent magnet. Its armature winding is polyphase winding, generally three-phase, can be connected into a star or triangle. Each phase winding is separately connected with a transistor switch in the electronic commutator circuit.
Abbreviated (BLDCM) - a type of synchronous motor. (BLDCM) is developed on the basis of brushed DC motor, but its driving current is unmitigated AC; Brushless DC motor can be divided into brushless speed motor and brushless torque motor. In general, the brushless motor (in principle, it is divided into DC brushless motor and AC brushless motor) has two kinds of driving current, one is trapezoidal wave (generally "square wave"), and the other is sine wave. Sometimes the former is called DC brushless motor (in principle, the trapezoidal wave voltage is also an AC voltage, but the square wave is more like "direct current", so it is called DC brushless motor.) The latter is called AC servo motor (to be exact, it is a kind of AC servo motor.)
In order to reduce the moment of inertia, brushless DC motors usually adopt a "slender" structure. The brushless DC motor is much smaller in weight and volume than the brushless DC motor, and the corresponding moment of inertia can be reduced by about 40%-50%. Due to the processing problems of permanent magnet materials, brushless DC motors are generally below 100kW brushless DC motors.
This motor has good linearity of mechanical characteristics and adjustment characteristics, wide speed range, long life, easy maintenance and low noise, and there is no series of problems caused by brushes, so this motor has great application potential in control systems.
The stator winding of the motor is mostly made of three-phase symmetrical star connection, which is very similar to the three-phase asynchronous motor (you can see the connection, also known as induction motor). A magnetized permanent magnet is attached to the rotor of the motor, and a position sensor is installed in the motor to detect the polarity of the rotor. The driver is composed of power electronic devices and integrated circuits, etc. Its function is: to accept the start, stop and brake signals of the motor to control the start, stop and brake of the motor; The position sensor signal and positive and negative turning signal are accepted to control the on-off of each power tube of the inverter bridge to generate continuous torque; Receive speed instructions and speed feedback signals to control and adjust the speed; Provide protection and display and more.
Because the brushless DC motor is operated by automatic control, it will not be like the synchronous motor that starts under the frequency conversion speed regulation, the rotor of the synchronous motor uses DC excitation, and can not start by itself, mostly using two methods of synchronous start and asynchronous start. Synchronous start is to drag the synchronous motor to the synchronous speed by another auxiliary motor, connect the power supply at the same time for excitation, and pull in the synchronous by the fixed rotor magnetic field. This starting method is too complicated and rarely used in practice. Asynchronous start is to short-circuit the motor rotor excitation winding through a resistor, when the speed is close to the synchronous speed, remove the resistance and add the excitation power at the same time, and then pull the fixed rotor magnetic field into the synchronous. Because of the number of turns of the excitation winding, the excitation winding cuts the rotating magnetic field and produces high voltage when the heavy load is started, which is easy to break down the winding and cause personal electric shock. In this way, the additional starting winding on the rotor will not cause oscillation and out-of-step when the load changes.
Because the brushless DC motor has the characteristics of DC brushed motor, it is also a frequency change device, so it is also known as DC frequency conversion, and the international common term is BLDC. The operation efficiency, low speed torque, speed accuracy and so on of brushless DC motor are better than any inverter control technology, so it is worth the attention of the industry. This product has produced 250w bldc motors to 20kw bldc motors, which can solve the needs of power saving and high-performance drive in the industry.
Post time: 2024-02-03 14:54:13
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