Ada dua kondisi ekstrim:
a. mereka yang memiliki kesempatan/kemampuan memilih
b. Mereka yang tidak punya pilihan.
Aku bersyukur karena termasuk golongan a. memiliki kesempatan memilih: diantaranya : memilih memperbudak materai dari pada diperbudak materi.
Menurut pak Wardi Utama, teman ronda ku di Mesan, setiap manusia pasti diberi kesempatan oleh Tuhan untuk memilih, sebagai contoh, pak Wardi mengidap asam urat, banyak pantangannya, sehingga “terpaksa memilih” tidak makan yang menyebabkan penyakitnya kambuh dari merasakan sakit akibat melanggar pantangannya.
Menurut aku kondisi pak Wardi dapat digolongkan b. Tidak punya pilihan, walau dia merasa punya pilihan, namun atas dasar “keterpaksaan”, bukan atas keinginannya.
Pak Wardi menyangkal dan menyatakan bahwa tidak makan pantangan, tidak menyebabkan kematian, sebab masih tersedia makanan lainnya.
Aku memberi contoh konkrit: Rakyat yang teramat miskin, juga tidak akan mati kelaparan kalau mereka mau makanan sisa atau mencari makanan dalam keranjang sampah.
Padahal ada kesempatan mencuri, tetapi karena”tak berani menanggung risikonya” , mereka terpaksa memilih mengorek sampah sekedar tetap bertahan hidup dari pada harus menanggung risiko mencuri. Aku menggolongkan rakyat yang sedemikian miskin sebagai golongan b. tidak memiliki pilihan.
Belakangan aku dihadapkan pada “menghilangnya’ bahan bakar minyak”. Kendaraan bermotor ku tidak dapat berjalan, sebab kehabisan bahan bakar, akan membeli tak ada yang menjual , walau sebenarnya aku punya uang untuk membeli dengan harga lebih mahal, misalnya membeli premium tak bersepsidi atau pertamak, baik di SPBU atau penjual eceran.
Apakah aku menjadi golongan b. yang tidak memiliki kesempatan memilih? Sekali lagi aku bersyukur karena tidak “konyol” akibat menghilangnya bahan bakar minyak.
Jika tanpa bahan bakar minyak aku konyol , berarti aku diperbudak oleh bahan bakar minyak. Aku bersyukur karena sanggup membeli sepeda ontel dengan memperbudak uang, sebab terbukti ada yang menjual sepeda ontel.
Mereka yang tidak mampu membeli sepeda ontel punya pilihan untuk meminjam atau mencuri sepeda orang lain. Mereka juga punya pilihan: jalan kaki sebab tak punya uang untuk membeli sepeda ontel bahkan tidak memiliki uang untuk naik ojek atau kendaraan umum. Dengan jalan kaki mereka juga dapat sampai ke tujuan, dari pada meminta sedekah dengan mengorbankan martabatnya.
Kesempatan memilih memang selalu tersedia, sebab Tuhan YME menyediakan segalanya, namun Tuhan YME juga memberikan kesadaran untuk mengurusi diri sendiri, jenis dan lingkungannya.
Berdasar kesadaran itu masing-masing akan memilih yang diinginkan dan “menisbikan” yang tidak diinginkan. Bagi golongan a. memiliki kesempatan untuk memilih apa yang diinginkan sedangkan golongan b. terpaksa memilih apa yang sebenarnya tidak diinginkan.
Dengan bersepeda ontel aku tidak lagi bergantung pada bahan bakar minyak. Kelangkaan bahan bakar minyak ternyata menyebabkan jalan tidak seramai biasanya sehingga aku merasa nyaman bersepeda ontel.
Jika kondisi jalan sedang ramai mungkin berjalan kaki dapat lebih dulu sampai ke tujuan dari pada menggunakan kendaraan roda dua apalgi roda ampat.
Saat tersedia lagi bahan bakar minyak, jalan kembali ramai, bahkan semakin padat. Aku tetap menggunakan sepeda ontel, karena antrean panjang bbm masih panjang. Bersepeda kurasa masih tetap “nyaman”, namun “keselamatan” ku tidak terjamin.
Diana Wyn Som, menantukan, memperingatkanku agar tidak menggunakan sepeda ontel sebab tidak tersdia jalur khusus bersepeda.
Aku berniat membeli sepeda listrik, sebab tidak perlu mengontel yang menyebabkan kondisi kurang stabil, Kelengkapa sepeda listrik mendekati sepeda motor mesin, misalnya kaca spion, klakson, lampu penunjuk arah, lampu rem dsb.
Oerip, adik iparku, memberitahu toko yang menjual sepeda listrik, harganya sekitar Rp 5.500.000,- di Jalan Magelang.
Kubaca folder, di dalamnya tidak tercantum tulisan “brushless motor” sehingga aku bertanya pada pencaga dagangan tsb.
“Apa itu brushless motor?” tanya mbak-mbak penjaga dengan polos.
“Motor listrik yang tidak menggunakan sikat arang atau borstel.”
“Apa itu sikat arang?”
“Maaf mbak, saya ini mantan guru listrik STM Pembangunan Mrican merasa punya kewajiban mengorbitkan penggunaan sepeda listrik. Agar dagangan laku, mbak sebaiknya dapat menjelaskan kelebihan sepeda motor listrik dibanding sepeda motor mesin pembakaran dalam.” .
“Saya lulusan SMK jurusan mesin,tetapi kurang faham mengenai motor listrik. Bolehkah saya berguru pada bapak perihal motor listrik agar dapat menjelaskan kepada calon pembeli?
“Ini telpon saya: 0274. 716.7878.”
Mbak-mbak itu datang ke rumah kami dan berkenalan dengan Endang, namun karena Endang akan segera memberi kuliah di AMY kami titinggalkan berduaan.
Aku sudah menyediakan denah dan penjelasan perihal “brusles electric motor” yang kudapat dari mesin pencari google.
Kuberi photo copy mengenai “brusless electric motor” untuk dipelajari atau diberikan kepada majikannya untuk memberi motivasi kepada calon pembeli.
Inilah yang sangat dibutuhkan oleh para calon pengguna sepeda listrik:
Brushless DC electric motor
Brushless DC electric motor (BLDC motors, BL motors) also known aselectronically commutated motors (ECMs, EC motors) are synchronous motorsthat are powered by a DC electric source via an integrated inverter/switching power supply, which produces an AC electric signal to drive the motor. In this context, AC, alternating current, does not imply a sinusoidal waveform, but rather a bi-directional current with no restriction on waveform. Additional sensors and electronics control the inverter output amplitude and waveform (and therefore percent of DC bus usage/efficiency) and frequency (i.e. rotor speed).
Brushless motors may be described as stepper motors; however, the term stepper motor tends to be used for motors that are designed specifically to be operated in a mode where they are frequently stopped with the rotor in a defined angular position. This page describes more general brushless motor principles, though there is overlap.
Two key performance parameters of brushless DC motors are the motor constants Kv and Km.
- 1 Brushless vs. brushed motors
- 2 Controller implementations
- 3 Variations in construction
- 4 Applications
- 5 See also
- 6 References
- 7 External links
Brushless vs. brushed motors
Brushed DC motors develop a maximum torque when stationary, linearly decreasing as velocity increases. Some limitations of brushed motors can be overcome by brushless motors; they include higher efficiency and a lower susceptibility to mechanical wear. These benefits come at the cost of potentially less rugged, more complex, and more expensive control electronics.
A typical brushless motor has permanent magnets which rotate around a fixed armature, eliminating problems associated with connecting current to the moving armature. An electronic controller replaces the brush/commutator assembly of the brushed DC motor, which continually switches the phase to the windings to keep the motor turning. The controller performs similar timed power distribution by using a solid-state circuit rather than the brush/commutator system.
Brushless motors offer several advantages over brushed DC motors, including more torque per weight, more torque per watt(increased efficiency), increased reliability, reduced noise, longer lifetime (no brush and commutator erosion), elimination of ionizing sparks from the commutator, and overall reduction of electromagnetic interference (EMI). With no windings on the rotor, they are not subjected to centrifugal forces, and because the windings 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 motor’s internals can be entirely enclosed and protected from dirt or other foreign matter.
Brushless motor commutation can be implemented in software using a microcontroller or microprocessor computer, or may alternatively be implemented in analogue hardware, or in digital firmware using an FPGA. Commutation with electronics instead of brushes allows for greater flexibility and capabilities not available with brushed DC motors, including speed limiting, “micro stepped” operation for slow and/or fine motion control, and a holding torque when stationary.
When converting electricity into mechanical power, brushless motors are more efficient than brushed motors. This improvement is largely due to the brushless motor’s velocity being determined by the frequency at which the electricity is switched, not the voltage. Additional gains are due to the absence of brushes, which reduces mechanical energy loss due to friction. The enhanced efficiency is greatest in the no-load and low-load region of the motor’s performance curve. Under high mechanical loads, brushless motors and high-quality brushed motors are comparable in efficiency.[disputed ]
Environments and requirements in which manufacturers use brushless-type DC motors include maintenance-free operation, high speeds, and operation where sparking is hazardous (i.e. explosive environments) or could affect electronically sensitive equipment.
Because the controller must direct the rotor rotation, the controller requires some means of determining the rotor’s orientation/position (relative to the stator coils.) Some designs use Hall effect sensors or a rotary encoder to directly measure the rotor’s position. Others measure the back EMF in the undriven coils to infer the rotor position, eliminating the need for separate Hall effect sensors, and therefore are often called sensorless controllers.
A typical controller contains 3 bi-directional outputs (i.e. frequency controlled three phase output), which are controlled by a logic circuit. Simple controllers employ comparators to determine when the output phase should be advanced, while more advanced controllers employ a microcontroller to manage acceleration, control speed and fine-tune efficiency.
Controllers that sense rotor position based on back-EMF have extra challenges in initiating motion because no back-EMF is produced when the rotor is stationary. This is usually accomplished by beginning rotation from an arbitrary phase, and then skipping to the correct phase if it is found to be wrong. This can cause the motor to run briefly backwards, adding even more complexity to the startup sequence. Other sensorless controllers are capable of measuring winding saturation caused by the position of the magnets to infer the rotor position.
Variations in construction
Brushless motors can be constructed in several different physical configurations: In the ‘conventional’ (also known as inrunner) configuration, the permanent magnets are part of the rotor. Three stator windings surround the rotor. In the outrunner (or external-rotor) configuration, the radial-relationship between the coils and magnets is reversed; the stator coils form the center (core) of the motor, while the permanent magnets spin within an overhanging rotor which surrounds the core. The flat or axial flux type, used where there are space or shape limitations, uses stator and rotor plates, mounted face to face. Outrunners typically have more poles, set up in triplets to maintain the three groups of windings, and have a higher torque at low RPMs. In all brushless motors, the coils are stationary.
There are two common electrical winding configurations; the delta configuration connects three windings to each other (series circuits) in a triangle-like circuit, and power is applied at each of the connections. The Wye (Y-shaped) configuration, sometimes called a star winding, connects all of the windings to a central point (parallel circuits) and power is applied to the remaining end of each winding.
A motor with windings in delta configuration gives low torque at low speed, but can give higher top speed. Wye configuration gives high torque at low speed, but not as high top speed.
Although efficiency is greatly affected by the motor’s construction, the Wye winding is normally more efficient. In delta-connected windings, half voltage is applied across the windings adjacent to the driven lead (compared to the winding directly between the driven leads), increasing resistive losses. In addition, windings can allow high-frequency parasitic electrical currents to circulate entirely within the motor. A Wye-connected winding does not contain a closed loop in which parasitic currents can flow, preventing such losses.
From a controller standpoint, the two styles of windings are treated exactly the same.
Brushless motors fulfill many functions originally performed by brushed DC motors, but cost and control complexity prevents brushless motors from replacing brushed motors completely in the lowest-cost areas. Nevertheless, brushless motors have come to dominate many applications particularly devices such as computer hard drives and CD/DVD players. Small cooling fans in electronic equipment are powered exclusively by brushless motors. They can be found in cordless power tools where the increased efficiency of the motor leads to longer periods of use before the battery needs to be charged. Low speed, low power brushless motors are used indirect-drive turntables for gramophone records.
A number of electric bicycles use brushless motors that are sometimes built into the wheel hub itself, with the stator fixed solidly to the axle and the magnets attached to and rotating with the wheel.
Heating and ventilations
There is a trend in the HVAC and refrigeration industries to use brushless motors instead of various types of AC motors. The most significant reason to switch to a brushless motor is the dramatic reduction in power required to operate them versus a typical AC motor. While shaded-pole and permanent split capacitor motors once dominated as the fan motor of choice, many fans are now run using a brushless motor.[when?] Some fans use brushless motors also in order to increase overall system efficiency.
In addition to the brushless motor’s higher efficiency, certain HVAC systems (especially those featuring variable-speed and/or load modulation) use brushless motors because the built-in microprocessor allows for programmability, better control over airflow, and serial communication.
The application of brushless DC motors within industrial engineering primarily focuses on manufacturing engineering orindustrial automation design. In manufacturing, brushless motors are primarily used for motion control, positioning oractuation systems.
Brushless motors are ideally suited for manufacturing applications because of their high power density, good speed-torque characteristics, high efficiency and wide speed ranges 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 systems
Brushless motors are commonly used as pump, fan and spindle drives in adjustable or variable speed applications. They can develop high torque with good speed response. In addition, they can be easily automated for remote control. Due to their construction, they have good thermal characteristics and high energy efficiency. To obtain a variable speed response, brushless motors operate in an electromechanical system that includes an electronic motor controller and a rotor position feedback sensor.
Brushless dc motors are widely used as servomotors for machine tool servo drives. Servomotors are used for mechanical displacement, positioning or precision motion control. In the past DC stepper motors were used as servomotors; however, since they are operated with open loop control, they typically exhibit torque pulsations. Brushless dc motors are more suitable as servomotors since their precise motion is based upon a closed loop control system that provides tightly controlled and stable operation.
Positioning and actuation systems
Brushless motors are used in industrial positioning and actuation applications. For assembly robots, brushless stepperor servo motors are used to position a part for assembly or a tool for a manufacturing process, such as welding or painting. Brushless motors can also be used to drive linear actuators
Actuator that produce linear motion is called linear motors. The advantage of linear motors is that they can produce linear motion without the need of a transmission system, such as a ball-and-lead screw, rack-and-pinion, cam, gears or belts, that would be necessary for rotary motors. Transmission systems are known to introduce less responsiveness and reduced accuracy. Direct drive, brushless DC linear motors consist of a slotted stator with magnetic teeth and a moving actuator, which has permanent magnets and coil windings. To obtain linear motion, a motor controller excites the coil windings in the actuator causing an interaction of the magnetic fields resulting in linear motion.
Brushless motors are a popular motor choice for model aircraft including helicopters. Their favorable power-to-weight ratios and large range of available sizes, from under 5 gram to large motors rated at well into the kilowatt output range, have revolutionized the market for electric-powered model flight, displacing virtually all brushed electric motors. They have also encouraged a growth of simple, lightweight electric model aircraft, rather than the previous internal combustion enginespowering larger and heavier models. The large power-to-weight ratio of modern batteries and brushless motors allows models to ascend vertically, rather than climb gradually. The low noise and lack of mess compared to small glow fuel internal combustion engines is another reason for their popularity.
Legal restrictions for the use of combustion engine driven model aircraft in some countries[clarification needed] have also supported the shift to high-power electric systems.
Radio controlled cars
Their popularity has also risen in the radio controlled car area. Brushless motors have been legal in North American RC car racing in accordance to ROAR since 2006. These motors provide a great amount of power to RC racers and, if paired with appropriate gearing and high-discharge Li-Po (lithium polymer) or considerably safer LiFePO4 batteries, these cars can achieve speeds over 161 kilometres per hour (100 mph).
Brushless motors are capable of producing more torque and have a larger peak RPM compared to nitro or gasoline powered engines. Nitro engines peak at around 26,000 RPM and 1.25HP, while a smaller brushless motor can reach 50,000 RPM and 5HP.
- Frank Julian Sprague#Joining the emerging electrical industry
- Electric motor#The first electric motors
- T.G. Wilson, P.H. Trickey, “D.C. Machine. With Solid State Commutation”, AIEE paper I. CP62-1372, October 7, 1962
- M. Gopal. Control systems: principles and design. 2nd ed. Tata McGraw-Hill, 2002. Page 165.
- Curie temperature
- PatentStorm’s time has ended
- ECMs and HVAC Systems
- Ohio Electric Motors. Brushless DC Motors Used in Industrial Applications. Ohio Electric Motors. 2012. Archived 12 October 2012 at WebCite
- Ohio Electric Motors. DC Motor Protection. Ohio Electric Motors. 2011. Archived 7 July 2011 at WebCite
- Sabrie Soloman. Sensors handbook. 3rd ed. McGraw-Hill, 1999. Page 5-6.
- Pter Campbel. Permanent Magnet Materials and their Application. Cambridge University Press, 1996. Page 172.
- M. Gopal. Control systems: principles and design. 2nd ed. Tata McGraw-Hill, 2002. Page 159.
- Shimon Y. Nof, Wilbert E. Wilhelm and Hans-Jürgen Warnecke. Industrial assembly. Springer, 1997. Page 174.
- Peng Zhang. Industrial Control Technology: A Handbook for Engineers and Researchers. William Andrew, Inc., 2008. Page 91.
- Ohio Electric Motors. Brushless DC Motors Used in Industrial Applications. Ohio Electric Motors. 2012. 1Archived 12 October 2012 at WebCite
|Wikimedia Commons has media related to Brushless DC electric motors.|
- How Motors Work (brushed and brushless RC airplane motors)
- Animation of BLDC Motor in different commutation (Block, Star, Sinus (sine) & Sensorless) – compared to stepper motors. Flash
- RC Hobby Mysteries: What is Brushless Motor
- Electric Drives – Brushless DC / AC and Reluctance Motors with useful diagrams