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Brushless DC motor: specifics, advantages, device device

June 6, 2020

A direct current motor is called an electric motor, which is powered by direct current. If necessary, get a high-torque engine with relatively low revolutions. Structurally, Inrunners are simpler because of that, that a stationary stator can serve as a housing. Fasteners can be mounted to it. In the case of Outrunners, the entire exterior rotates. The motor is mounted on a stationary axis or stator parts. In the case of a motor-wheel, the fastening is carried out by the stationary axis of the stator, the wires are wound to the stator through a hollow shaft of fewer 0,5 mm.

Types of electric motors

There are following types of DC motors:

  • with disturbance by means of permanent magnets;
  • with a series connection of the armature and excitation windings;
  • with a parallel connection of the armature and excitation windings;
  • with a mixed connection of the armature and excitation windings;
  • valve engine (brushless direct current motor), made using a closed system; this type of motor uses an inverter (power semiconductor converter), coordinate converter and DPR (rotor position sensor).

An alternating current motor is called an electric motor, which is powered by alternating current. There are the following types of AC motors:

  • hysteresis motor;
  • valve jet engine;
  • asynchronous electric motor with a frequency of rotation of the rotor, which differs from the rotation frequency is created by the magnetic field voltage;
  • synchronous electric motor with the frequency of rotation of the rotor, coinciding with the rotation frequency is created by the magnetic field voltage.

There is also UKD (universal collector engine) with the function of the operating mode as on the variable, as well as on direct current.

Another type of motor is a stepper motor with a finite number of rotor positions. A certain specified position of the rotor is fixed by applying power to the necessary corresponding windings. When the supply voltage is removed from one winding and its transfer to others, the process of transition to another position occurs.

An AC motor when powered by an industrial network usually does not allow to reach a rotation frequency of more than three thousand revolutions per minute. For this reason, if it is necessary to obtain higher frequencies, a collector motor is used, the additional advantages of which are lightness and compactness while maintaining the necessary power.

Sometimes a special transmission mechanism called a multiplier is also used, which changes the kinematic parameters of the device to the required technical indicators. Manifold assemblies sometimes occupy up to half of the engine space, therefore, AC motors are reduced in size and made lighter in weight by using a frequency converter, and sometimes due to the presence of a network with an increased frequency to 400 Hz.

The resource of any AC asynchronous motor is significantly higher than that of a collector. It is determined by the state of insulation of windings and bearings. A synchronous motor when using an inverter and a rotor position sensor is considered an electronic analogue of a classic collector motor, which supports operation with direct current.

Brushless direct current electric motor. General information and device device

A brushless DC motor is also called a three-phase valve motor. It is a synchronous device, the principle of operation of which is based on self-synchronized frequency regulation, thanks to which vector control takes place (pushing off from the position of the rotor) magnetic field of the stator.

Electric motor controllers of this type are often powered by constant voltage, from which they got their name. In the English-language technical literature, the valve electric motor is called PMSM or BLDC.

The brushless motor was created primarily to optimize any DC motor as a whole. To the executive mechanism of such a device (especially to a high-speed micro-drive with precise positioning) very high demands were made.

It, apparently, and led to the use of such specific direct current devices, brushless three-phase motors, also called BDPT. By their design, they are almost identical to AC synchronous motors, where the rotation of the magnetic rotor occurs in a conventional charged stator in the presence of three-phase windings, and the number of revolutions depends on the voltage and loads of the stator. Based on the determined coordinates of the rotor, different stator windings are switched.

Brushless DC motors can exist without any separate sensors, however, sometimes they are present on the rotor, example, Hall Sensor. If the device works without an additional sensor, then the stator windings perform the function of a fixing element. Then the current arises due to the rotation of the magnet, when the rotor induces emf in the stator winding.

If one of the windings is turned off, then that signal will be measured and further processed, which was given, however, such a working principle is impossible without a professor of signal processing. But for reversing or braking such an electric motor, a bridge circuit is not required - it will be enough to apply control pulses to the stator windings in the reverse sequence.

VD (valve engine) the inductor in the form of a permanent magnet is located on the rotor, and the armature winding is on the stator. Based on the position of the rotor, the supply voltage of all windings of the electric motor is formed. When used in such collector designs, its function will be performed by a semiconductor switch in the valve engine.

The main difference between synchronous and valve motors is self-synchronization of the latter with the help of DPR, which determines the proportional frequency of rotation of the rotor and the field.

Most often, the DC motor without a collector is used in such areas:

  • freezing or refrigerating equipment (compressors);
  • electric drive;
  • air heating systems, its air conditioning or ventilation.

Stator

This device has a classic design and resembles the same device of an asynchronous machine. The composition includes a core made of copper winding (placed along the perimeter in grooves), which determines the number of phases, and body. Usually, sine and cosine phases are sufficient for rotation and self-starting, however, often, a valve engine is made three-phase and even four-phase.

Electric motors with reverse electromotive force are divided into two types according to the type of arrangement of turns on the stator winding:

  • sinusoidal shape;
  • trapezoidal shape.

In the corresponding types of the motor, the electric phase current also changes according to the sinusoidal or trapezoidal feeding method.

Rotor

Usually, the rotor is made of permanent magnets with the number of pairs of poles from two to eight, which, in turn, alternate from north to south or vice versa.

Ferrite magnets are considered the most common and cheapest for making a rotor, but their disadvantage is a low level of magnetic induction, therefore, devices are now coming to replace such material, created from alloys of various rare earth elements, because they can provide a high level of magnetic induction, what, in turn, allows to reduce the size of the rotor.

DPR

A rotor position sensor provides feedback. According to the principle of operation, the device is divided into the following subspecies:

  • inductive;
  • photoelectric;
  • hall effect sensor.

The last type gained the most popularity due to its almost absolute inertialess properties and the ability to get rid of the delay in the feedback channels depending on the position of the rotor.

Management system

The control system consists of power keys, sometimes also from thyristors or power transistors, which include an isolated shutter, leading to the collection of current inverter or voltage inverter. The process of managing these keys is implemented most often by using a microcontroller, which requires a huge number of computational operations to control the engine.