refers to a brushless DC motor with a low-power electronically commutated DC motors, also known as non-brush motor, DC motor without commutator. Trans equivalent to a DC motor mounted on the structure, which is placed on the armature of the stator, the rotor is a permanent magnet. Its armature winding is a multiphase winding, three-phase in general, can be connected in a star or triangle. Each phase winding are respectively connected to the transistor switches of the electronic commutator circuit.
1. Introduction brushless DC motor
A low-power direct current motor with electronic commutation. Also known as non commutator motor, a DC motor without commutator. Usually the mechanical commutator which is substituted by a DC motor in a semiconductor inverter, not constitute a DC motor commutator. This type of motor is simple structure, reliable operation, no spark, low electromagnetic noise, widely used in modern production equipment, instrumentation, computer peripherals and advanced home appliances.
by a brushless DC motor and synchronous motor drives and is a typical mechatronic products. The stator winding is made multi-phase synchronous motor symmetrical star-connection, three-phase asynchronous motor with very similar. While the rotor is magnetized adheredA permanent magnet rotor in order to detect the polarity of the motor, the motor built in the position sensor. Constituted by the power drive electronics and integrated circuits, which is: receiving the starter motor is stopped, the brake signal to control the motor start, stop, and braking; receiving position sensor signal and reversing signal for controlling an inverse each bridge variable power-off tube, continuous torque is generated; receiving speed command and the speed feedback signal to control and adjust the speed; protection, and a display and the like.
brushless DC motor controlled by the inverter and a position detector by controlling the composition. Small thyristor inverter type motor is generally composed of a transistor; large motor inverter thyristors usually referred to as a thyristor motor.
2. Brushless DC motor controlled inverter
used in the brushless DC motor is controlled inverter. It is different from the general inverter. Its output frequency is not independently adjustable, but is controlled by the rotor position detector installed in the synchronous motor shaft. Each time the rotor is rotated a predetermined position (e.g., 120 ° or 90 ° electrical angle), corresponding to the position detector will produce signals applied to the corresponding semiconductor elements, the respective phase winding is energized, torque is generated. Each motor rotor is rotated through a pair of magnetic poles, each of the semiconductor elements alternately conducting week AC inverter output cycle changes correspondingly. Therefore, the rotational speed of the motor and the output frequency-controlled inverter is always synchronized, step phenomenon does not occur.
In a small brushless DC motor, the inverter of transistors. Since the transistor having a self turn-off capability, as long as the control signal disappears on its base, the transistor wouldSelf-off, the control is relatively simple. In the larger capacity of the brushless DC motor, a thyristor inverter. No self-turn-off thyristor ability, can not rely on it to remove the trigger signal is turned off. So when a phase current need off, so that another phase is energized, the pilot how to pass the original off thyristor, the current is transferred to a new phase of a thyristor, i.e., between the thyristor commutation problem is the key technology of the thyristor motor.
3. The brushless DC motor position detector
mounted on the motor shaft of the rotor position detector is an important component of the brushless DC motor. It determines the start timing of the armature windings of each phase energization. It acts general DC motor brushes. Changing the position of the time change detector generates a signal in the spatial position of the brush (phase), is equivalent to the DC motor, it has a great influence on the characteristics of the brushless DC motor. Many structural types of position detector, which typically includes a set of stationary detection element and the position signal is formed with a rotor rotating together. In the position detector composed of a Hall element, a Hall element is detecting element, and the rotor magnetic pole position signal itself is formed. In other configurations, the electromagnetic induction type, photoelectric type, press-type proximity switch, often using a notched disc as a position signal forming device. For example, using this gap to make the light irradiated on the photoelectric generating a signal in a photoelectric tube; electromagnetic induction by the gap opening of the magnetic circuit of the transformer changes, the detection coil generates an electromotive force and so on.
Characteristics of the brushless DC motor 4
Good external characteristics of the brushless DC motor, capable of outputting a large torque at low speed, so that it can provide a large starting torque;. Speed of the brushless DC motor wide range, can be run at full power at any speed; high efficiency brushless DC motor, overload strong, so that it has excellent performance in the drive system; good regenerative braking effect of the brushless DC motor, because of its the rotor is a permanent magnet material, may enter the motor generator during braking state; brushless DC motor of small size, high power density; brushless DC motor without mechanical commutator, a fully enclosed structure, dust can be prevented from entering the interior of the motor high reliability; brushless DC motor drive control is simpler than asynchronous motors.