Brushless DC electric motors ( BLDC motors , BL motors ) also known as electronically mutated motors (ECMs, motors EC)), or synchronous DC motor , is a synchronous motor powered by DC power through an inverter or switching power supply that generates AC power to drive each phase of the motor through a closed-loop controller. The controller delivers a current pulse to the motor windings that controls the speed and torque of the motor.
Construction of a brushless motor system is typically similar to a permanent magnet synchronous (PMSM) motor, but can also be a switching, switchgear, or induction motor (asynchronous).
The advantage of brushless motor over brushed motor is the high power ratio to weight, high speed, and electronic control. Brushless motors find applications in places like computer peripherals (disk drives, printers), handheld power tools, and vehicles ranging from model airplanes to cars.
Video Brushless DC electric motor
Motor Brushless vs. brushed
Brushed DC motor was created in the 19th and general century. The brushless DC motor was made possible by the development of solid state electronics in the 1960s.
An electric motor develops torque by alternating the rotating magnetic polarity attached to the rotor, the engine turning, and the stationary magnet on the stator that surrounds the rotor. One or both sets of magnets are electromagnets, made of wire coils that surround the iron core. DC runs through a winding wire creating a magnetic field, providing the power that runs the motor. However, whenever the rotor rotates 180 Â ° (half round), the position of the north and south poles on the rotor is reversed. If the magnetic field of the poles remains the same, this will cause a torque reversal on the rotor every half-turn, so that the average torque will be zero and the rotor will not change. Therefore, in DC motors, to create torque in one direction, the direction of electric current through the winding must be reversed with each 180 ° rotor rotation (or switched off during that time in the wrong direction). This reverses the direction of the magnetic field when the rotor rotates, so that the torque on the rotor is always in the same direction.
Commutator
In a brushed motor, discovered in the 19th century, this is done with a rotary switch on the motor shaft called a commutator. It consists of a spinning cylinder divided into several metal contact segments on the rotor. The segment is connected to an electromagnetic wire coil on the rotor. Two or more stationary contacts called "brushes", are made of soft conductors such as graphite which compress the commutator, making electrical contacts shift with successive segments as the rotor rotates, providing electric current to the windings. Each time the rotor rotates 180 Â °, the commutator reverses the direction of the applied electric current to the given winding, so that the magnetic field creates torque in one direction.
Lack of commutator
The commutator has many engineering losses that cause a decrease in the use of brushed motors. These losses are:
- The brush friction that shifts along the rotary commutator segment causes significant power losses in low power motors.
- Soft brush material fade due to friction, create dust, and finally brush should be replaced. This makes the motor being routed unsuitable for low or sealed particulate applications such as hard disk motors.
- The resistance of sliding brush contacts causes a decrease in voltage across motor circuits called "brush drops" that consume energy. This can amount to several volts, so in a low voltage motor this could be a significant power loss.
- A recurrent switching of current through the winding inductance causes a spark to the commutator's contact. It is a fire hazard in the explosive atmosphere, and creates an electronic sound, which can cause electromagnetic interference in nearby microelectronic circuits.
Over the past hundred years the brushed high-power DC motor, once it became the industry's mainstay, was replaced by an alternating current sync motor (AC). Currently the brushed motor is used only in low power applications where only DC is available, but the above deficiencies limit its usage even in this application. Brushless motor was created to solve this problem.
Brushless Solution
The development of semiconductor electronics in the 1970s allowed commutators and brushes to be eliminated in DC motors. In brushless DC motors, electronic servo systems replace mechanical commutator contacts. An electronic sensor detects a rotor angle, and controls a semiconductor switch such as a current-switched transistor through a roll, either reversing the direction of the current, or on some of its lethal motors, at exactly the right time of rotation of 180 ° axis so that the electromagnet creates torque in one direction. Removal of the slide contact allows the brushless motor to have less friction and longer life; their working life is limited only by their lifetime.
The brushed DC motor develops maximum torque when stationary, linearly decreases as speed increases. Some limitations of brushed motors can be overcome with brushless motors; they include higher efficiency and lower susceptibility to mechanical wear. These benefits come with potentially less costly, more complicated, and more costly control electronics.
The typical brushless motor has a permanent magnet that rotates around the fixed armature, eliminating the problems associated with connecting the current to the mobile armature. The electronic controller replaces the brush/commutator assembly of the brushed DC motor, which continuously diverts the phase to the winding to maintain motor rotation. The controller performs the same time power distribution using a solid-state circuit rather than a brush/commutator system.
Brushless motors offer several advantages over brushed DC motors, including high torque to weight ratio, more torque per watt (increased efficiency), increased reliability, noise reduction, longer lifetime (no brush erosion and commutator), spark removal ionization of the commutator, and overall reduction of electromagnetic interference (EMI). Without rolls on the rotor, they do not experience centrifugal force, and since the coils are supported by the housing, they can be cooled by conduction, requiring no airflow inside the motor for cooling. This in turn means that the internal motor can be completely covered and protected from dirt or other foreign matter.
Brushless motor shifts can be implemented in software using a microcontroller or microprocessor computer, or can be applied alternatively in analog hardware, or in digital firmware using an FPGA. Substitution with non-brush electronics enables greater flexibility and capability not available with brushed DC motors, including speed limiting, micro-stepping operations for slow and/or smooth motion control, and torque holding when stationary. Controller software can be tailored to the specific motors used in the application, resulting in greater turnover efficiency.
The maximum strength that can be applied to a brushless motor is limited almost exclusively by heat; too much heat weakens the magnet and will damage the winding insulation.
When turning electricity into engine power, a brushless motor is more efficient than a brushed motor. This increase is mostly due to the frequency at which the power is switched is determined by the position sensor feedback. An additional advantage is that there is no brush, which reduces mechanical energy loss due to friction. The largest increase in efficiency in the no-load and low-load areas of the motor performance curve. Under high mechanical loads, brushless motors and high quality brush motors are comparable in efficiency.
The environment and requirements under which manufacturers use brushless DC motors include maintenance-free, high-speed operations and operations where hazardous sparks (ie, explosive environments) or can affect electronically sensitive equipment.
The construction of a brushless motor may resemble a stepper motor. Unlike stepper, the brushless motor is usually intended to produce continuous rotation. The stepper motor generally does not include the shaft position sensor for internal feedback from the rotor position. Instead the stepper controller will depend on the sensor to detect the position of the driven device. They often stop with the rotor in the specified angle position while still generating torque. Well designed brushless motor systems can also be performed on zero rpm and limited torque.
Maps Brushless DC electric motor
Implementation controller
Since the controller implements the traditional brushes function, rotor orientation or position (relative to the stator coil) is required. It is automatic in a motor brushed due to rotor geometry and fixed rotor brush. Some designs use Hall effect sensors or rotary encoder to directly measure the rotor position. Others measure back-EMFs in undriven windings to infer rotor positions, eliminating the need for separate Hall effect sensors, and are therefore often called sensorless controllers.
The typical controller contains 3 bi-directional outputs (ie, frequency controlled three-phase output), which is controlled by a logic circuit. The simple controller uses a comparator to determine when the output phase should be increased, while the more advanced controller uses a microcontroller to manage acceleration, control speed and tuning efficiency.
Controllers that perceive rotor positions based on back-EMF have additional challenges in initiating movement since no back EMF is generated when the rotor is stationary. This is usually achieved by the initial rotation of the arbitrary phase, and then jumps to the correct phase if found wrong. This can cause the motor to run at a glance backward, adding more complexity to the startup sequence. Other sensorless controls are able to measure the saturation of the windings caused by the position of the magnet to infer the rotor position.
The two main performance parameters of brushless DC motor are motor constants K T (torque constant) and K e (constant back -EMF is also known as the constant velocity K V = 1/ K e ).
In SI units the K T and K V are the same constants:
Variasi dalam konstruksi
Brushless motors can be built in several different physical configurations: In a 'conventional' configuration (also known as inrunner ), the permanent magnet is part of the rotor. Three stator windings surround the rotor. In the sprint (or external-rotor) configuration, the radial relationship between the coil and magnet is reversed; the stator coil forms the center (core) of the motor, while the permanent magnet rotates inside the rotor jutting around the core. A flat or axial flux type, used where there is space or form of limitations, using a stator and rotor plate, is mounted face-to-face. Outrunners usually have more poles, arranged in triplets to retain three clusters of rolls, and have higher torque at lower RPM. In all brushless motors, the coil is silent.
There are two general electric winding configurations; the delta configuration connects three windings to one another (series circuit) in a circuit like a triangle, and power is applied to each connection. The Wye configuration ( Y ), sometimes called the star winding, connects all the entanglement to the center point (parallel circuit) and power is applied to the remaining end of each winding.
Motor with coil in delta configuration gives low torque at low speed, but can give top speed. The Wye configuration provides high torque at low speed, but does not have the highest speed.
Although efficiency is strongly influenced by motor construction, Wye's winding is usually more efficient. In a delta-connected reel, a half voltage is applied along the coil adjacent to the driven lead (as opposed to direct winding between the driven leads), increasing the resistive resistance. In addition, the windings can allow high-frequency parasitic electric currents to circulate entirely within the motor. Wye-connected winding does not contain a closed loop where parasitic currents can flow, preventing such losses.
From the controller's point of view, these two roll styles are treated exactly the same.
Apps
The brushless motor fulfills many of the functions originally performed by a brushed DC motor, but the complexity of charge and control prevents the brushless motor from replacing fully brushed motors in the lowest cost areas. Nevertheless, brushless motors have dominated many applications, especially devices such as computer hard drives and CD/DVD players. The small cooling fan in the electronic equipment is supported exclusively by the brushless motor. They can be found in cordless power tools where increased motor efficiency leads to longer periods of use before the battery needs to be charged. Low-speed, low power brushless motors are used in direct-drive turntables for LPs.
Transportation
Brushless motors are found in electric vehicles, hybrid vehicles and personal transporters, which are essentially synchronous AC motors with permanent magnetic rotor. Some electric bikes use a brushless motor that is sometimes built into the wheel hub itself, with the stator firmly fixed to the shaft and magnet attached and spinning with the wheels. Most electric-powered RC models use brushless motors because of their high efficiency.
Cordless tools
Brushless motors are found in many modern cordless devices, especially weed hawkers, leaf blowers, and some drill/cordless drivers.
Heating and ventilation
There is a tendency in the HVAC and refrigeration industry to use brushless motors instead of various types of AC motors. The most significant reason for switching to a brushless motor is the dramatic reduction in power required to operate it over a common AC motor. While shaded polar and permanent split capacitor motors once dominated as fan motors, many fans now run using brushless motors. Some fans use brushless motors as well to improve overall system efficiency.
In addition to the higher efficiency of the brushless motor, the HVAC system (especially featuring variable-speed and/or load modulation) uses a brushless motor because the built-in microprocessor enables programmability, airflow control, and serial communications. Some ceiling fans and portable fans also feature this motor. They advertise motors that are very energy efficient and quieter than most fans.
Industrial engineering
The adoption of a brushless DC motor in industrial engineering primarily focuses on manufacturing engineering or industrial automation design. In manufacturing, brushless motors are mainly used for motion control, positioning or actuation systems.
The brushless motor is ideal for manufacturing applications due to its high power density, good torque speed characteristics, high efficiency, wide speed range and low maintenance. The most common uses of brushless DC motors in industrial engineering are linear motors, servomotors, actuators for industrial robots, extruder drive motors and feed drives for CNC machine tools.
Motion control system
Brushless motors are generally used as pumps, fans and drive spindles in adjustable or variable speed applications as they are capable of developing high torque with good speed response. In addition, they can be easily automated for remote control. Because of their construction, they have good heat characteristics and high energy efficiency. To obtain variable speed responses, the brushless motor operates in an electromechanical system that includes an electronic motor controller and a rotor position feedback sensor.
Brushless DC motor is widely used as servomotor for servo drive machine tool. Servomotors are used for mechanical displacement, positioning or precision motion control. In the past DC stepper motors are used as servomotors; However, since they are operated with open-loop controls, they usually show a torque pulsation. The brushless DC motor is more suitable as a servomotor because its precise motion is based on a closed-loop control system that provides tightly controlled and stable operation.
Positioning and actuation system
Brushless motors are used in industrial position and actuation applications. For assembly robots, a brushless stepper or servo motor is used to position parts for assembly or tools for manufacturing processes, such as welding or painting. Brushless motors can also be used to drive linear actuators.
The motor that directly produces a linear motion is called a linear motor. The advantage of linear motors is that they can produce linear motions without the need for transmission systems, such as ballscrews, leadscrew, rack-and-pinion, cam, gears or belt, which will be required for rotary motors. The transmission system is known to introduce less response and reduce accuracy. Direct drive, linear brushless DC motor consists of a hollow stator with magnetic gear and moving actuator, which has a permanent magnet and coils roll. To obtain linear motion, motor controller excites the coil windings in the actuator causing the interaction of the magnetic field to produce linear motion. Tubular linear motors are another form of linear motor design that is operated in the same way.
Aeromodelling
The brushless motor has become a popular motor choice for model aircraft including helicopters and unmanned aircraft. Its favorable strength-to-weight ratio and available sizes ranging from less than 5 grams to well-rated large motors into the kilowatt output range, have revolutionized the market for aviation-powered models, replacing almost all brushed electric motors. They also encouraged the growth of simple and lightweight electric model aircraft, rather than previous internal combustion engines that produced larger and heavier models. An increase in the power-to-weight ratio of modern batteries and brushless motors allows the model to rise vertically, rather than step by step. The low noise and lack of mass compared to the internal combustion engines of small light fuel are another reason for their popularity.
Legal restrictions for the use of engine-driven model aircraft in some countries, most often because of the potential for noise pollution - even with mufflers designed especially for most model engines available over the past few decades - have also supported the shift to high-powered electric systems.
Radio-controlled cars
Their popularity is also increasing in the area of ​​radio-controlled cars (RCs). The brushless motor has been legal in North American RC car races in accordance with ROAR since 2006. This motor provides a large amount of power for the RC racers and, when paired with suitable gear and high Li-Po (lithium polymer) or LiFePO4 Li-ion batteries, this car can reach speeds of over 160 kilometers per hour (99 mph).
The brushless motor is capable of producing more torque and has a faster peak rotation speed compared to a nitro engine or gasoline engine. The nitro engine reaches about 46,800 r/min and 2.2 kW (~ 2.95 hp), while smaller brushless motors can reach 50,000 r/min and 3.7 kW (~ 5 hp). Larger brushless RC motors can reach over 10 kW (~ 13.4 hp) and 28,000 r/mnt for power 1 / 5 th scale model.
See also
- Squirrel-cage rotors
Literature
- Jacek F. Gieras; Mitchell Wing (2002), Permanent magnetic motor technology: design and application , CRC Press
- Krishnan Ramu (2009), Permanent Magnetic Motor Trunk and Brushless DC , Press CRC
- Howard E. Jordan (1994), Energy-saving electric motor and its application , Springer
- Bobby A. Bassham (2003), Evaluation of Electric Motors for Propulsion Ship , Navy Graduate School
References
External links
- How Motor Works (RC brushed and brushless aircraft motors)
- BLDC animation Motor in different turns (Block, Star, Sinus (sinus) & Uncensored) - compared to stepper motor. Flash
- Mystery of RC Hobby: What is a Motor Without Brush
- Electric Drives - Brushless DC/AC and Reluctance Motors with useful diagrams
- Brakeless DC motor regenerative brake for light electric vehicles
Source of the article : Wikipedia
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