Brushless DC Motor Fundamentals Application Note

Transcription

1 A047 Brushless DC otor Fundmentls Brushless DC otor Fundmentls Applition ote Prepred y Jin Zho/Yngwei Yu July 2011 A047 Rev /7/2014 P Proprietry Informtion. Ptent Proteted. nuthorized Photoopy nd Duplition Prohiited P. All Rights Reserved.

2 A047 Brushless DC otor Fundmentls ABTRACT This pplition note provides generl overview of BLDC motors, inluding their dvntges ginst other ommonly-used motors, struture, eletromgneti priniples, nd mode of opertion. This doument lso exmines ontrol priniples using Hll sensors for oth single-phse nd three-phse BLDC motors, nd rief introdution to sensorless ontrol methods using BEF for three-phse BLDC motor. A047 Rev /7/2014 P Proprietry Informtion. Ptent Proteted. nuthorized Photoopy nd Duplition Prohiited P. All Rights Reserved.

3 A047 BRHLE DC OTOR FDAETAL IDEX ABTRACT ITRODCTIO OTOR FDAETAL COCEPT Generl priniple of motor gneti fore Left-hnd rule Right-hnd rule... 6 d. Right-hnd srew rule ttor Rotor Opertion theory of motor ARIO OTOR TYPE rious types of motor introdution Brushed DC motor Brushless DC (BLDC) motor AC indution motor (ACI) d. Permnent mgnet synhronous motor (P) e. tepper motor & withed relutne (R) motor Comprison for vrious motor types BRHLE DC OTOR COTROL with onfigurtion nd P Eletronis ommuttion priniple ingle-phse BLDC motor Three-phse BLDC motor ensorless ontrol of BLDC motor ARY REFERECE: A047 Rev /7/2014 P Proprietry Informtion. Ptent Proteted. nuthorized Photoopy nd Duplition Prohiited P. All Rights Reserved.

4 A047 BRHLE DC OTOR FDAETAL 1. ITRODCTIO The BLDC motor is widely used in pplitions inluding pplines, utomotive, erospe, onsumer, medil, utomted industril equipment nd instrumenttion. The BLDC motor is eletrilly ommutted y power swithes insted of rushes. Compred with rushed DC motor or n indution motor, the BLDC motor hs mny dvntges: [1] Higher effiieny nd reliility Lower ousti noise mller nd lighter Greter dynmi response Better speed versus torque hrteristis Higher speed rnge Longer life This doument initilly provides generl overview to fmilirize the reder with motor ontrol fundmentls, terms nd onepts, nd pplitions. The ltter portion of this doument provides detiled desriptions of motor struture, working priniple, hrteristis nd ontrol methods. 2. OTOR FDAETAL COCEPT 2.1 Generl otor Priniples otors onvert eletril energy into mehnil energy using eletromgneti priniples. The energy onversion method is fundmentlly the sme in ll eletri motors. This doument strts with generl overview of si eletromgneti physis efore entering disussing the detils of motor opertion.. gneti Fore gneti poles generte invisile lines of mgneti fore flowing from the north pole to the south pole s shown in Figure 1. hen mgneti poles of opposite polrity fe eh other, they generte n ttrtive fore, while like poles generte repulsive fore. ) nlike-pole ttrtion () Like-pole repulsion Figure 1 gneti Fore. Left-Hnd Rule Current in ondutor genertes mgneti field. Pling ondutor in the viinity of seprte mgneti n generte fore tht rehes its pex when the ondutor is t 90 to the externl field. The left-hnd rule n help the user determine the diretion of the fore, s shown in Figure 2(). A047 Rev /7/2014 P Proprietry Informtion. Ptent Proteted. nuthorized Photoopy nd Duplition Prohiited P. All Rights Reserved.

5 A047 BRHLE DC OTOR FDAETAL Left-Hnd Rule: Extend the left hnd with the thum nd four fingers on the sme plne with the thum pointing out. Fe the plm towrds the north pole of the externl mgneti field nd the four fingers in the diretion of the urrent; the thum points in the diretion of the fore. F - + i e B B v () Left-Hnd Rule () Right-Hnd Rule Figure 2 Left-Hnd Rule nd Right-Hnd Rule The mgnitude of the fore n e lulted from the eqution elow: F = BIL sinθ (1) here F is the eletromgneti fore, B is the mgneti field density, I is the ondutor urrent, L is the length of the ondutor, nd θ is the ngulr differene etween B nd I. Given tht oil usully hs two effetive ondutors: - nd -d shown in Figure 3(), these two ondutors indue two fores of opposite diretion when urrent psses through in the mgneti field. L F i d O F OO r L v e d O e O F B r F O? r v B () () () Figure 3 Coil in gneti Field The torque is the produt of the tngentil fore ting t rdius with units of fore multiplied y length. If there re ontinuous oil turns, nd sed on the prmeters in Figure 3(), the generted torque equls: here: TD 2rF 2rBIL KTI = = = (2) T D is the eletromgneti torque ( m) r is the distne etween xis OO nd the ondutor (m) is the numer of winding turns K T =2rBL is the torque onstnt ( m/a). A047 Rev /7/2014 P Proprietry Informtion. Ptent Proteted. nuthorized Photoopy nd Duplition Prohiited P. All Rights Reserved.

6 A047 BRHLE DC OTOR FDAETAL. Right-Hnd Rule The movement of the ondutor in the mgneti field indues n eletromotive fore known s the BEF. The right-hnd rule n determine the diretion of the fore s shown in Figure 2(). The Right-Hnd Rule: treth out the right hnd with the four fingers nd the thum on the sme plne,the plm fing the north pole of the externl mgneti field, nd the thum pointing in the diretion of the veloity of v. The four fingers point in the diretion of the indued eletromotive fore. The mgnitude of the indued eletromotive fore n e lulted s: E = BLv sinθ (3) here: E is the indued eletromgneti fore (). v is the veloity of the ondutor (m/s). θ is the ngulr differene etween B nd L (rd). hen the motor rottes t n ngulr veloity of ω (rd/s) nd there re oil turns, the totl eletromotive fore is: E = 2BLv = 2BLω r = KEω (4) here: ω is the ngulr veloity (rd/s). r is the internl rdius of the motor (m). K E =2rBL is the eletromotive fore onstnt ( s/rd). Bsed on the prmeters from Figure 3() d. Right-Hnd Corksrew Rule Given tht n eletril urrent flowing in stright line genertes mgneti field s shown in Figure 4() oiling the ondutor would therefore generte ler mgneti poles s shown in Figure 4(), with the diretion of the mgneti fields determined y the right-hnd orksrew rule. Right-Hnd Corksrew Rule: For urrent flowing in stright line s shown in Figure 4(), the thum points in the diretion of the urrent I, nd the fingers url in the diretion of the mgneti field B. For oiled urrent s shown in Figure 4(), the fingers url in the diretion of the urrent I, nd then the thum points in the diretion of the mgneti field B through the enter of the loop. i i () tright line () Loop Figure 4 Right-Hnd Corksrew Rule A047 Rev /7/2014 P Proprietry Informtion. Ptent Proteted. nuthorized Photoopy nd Duplition Prohiited P. All Rights Reserved.

7 A047 BRHLE DC OTOR FDAETAL 2.2 ttor There re three lssifitions of the BLDC motor: single-phse, two-phse nd three-phse. This disussion ssumes tht the sttor for eh type hs the sme numer of windings. The single-phse nd three-phse motors re the most widely used. Figure 5 shows the simplified ross setion of single-phse nd three-phse BLDC motor. The rotor hs permnent mgnets to form 2 mgneti pole pirs, nd surrounds the sttor, whih hs the windings. ttor ttor Rotor Rotor A B Air gp A B C Air gp Permnent mgnets Permne nt mgnet () ingle-phse () Three-phse Figure 5 implified BLDC otor Digrms A single-phse motor hs one sttor winding wound either lokwise or ounter-lokwise long eh rm of the sttor to produe four mgneti poles s shown in Figure 5(). By omprison, threephse motor hs three windings s shown in Figure 5(). Eh phse turns on sequentilly to mke the rotor revolve. There re two types of sttor windings: trpezoidl nd sinusoidl, whih refers to the shpe of the k eletromotive fore (BEF) signl. The shpe of the BEF is determined y different oil interonnetions nd the distne of the ir gp. In ddition to the BEF, the phse urrent lso follows trpezoidl nd sinusoidl shpe. A sinusoidl motor produes smoother eletromgneti torque thn trpezoidl motor, though t higher ost due to their use of extr opper windings. A BLDC motor uses simplified struture with trpezoidl sttor windings. 2.3 Rotor A rotor onsists of shft nd hu with permnent mgnets rrnged to form etween two to eight pole pirs tht lternte etween north nd south poles. Figure 6 shows ross setions of three kinds of mgnets rrngements in rotor. There re multiple mgnet mterils, suh s ferrous mixtures nd rre-erth lloys. Ferrite mgnets re trditionl nd reltively inexpensive, though rre-erth lloy mgnets re eoming inresingly populr euse of their high mgneti density. The higher density helps to shrink rotors while mintining high reltive torque when ompred to similr ferrite mgnets. A047 Rev /7/2014 P Proprietry Informtion. Ptent Proteted. nuthorized Photoopy nd Duplition Prohiited P. All Rights Reserved.

8 A047 BRHLE DC OTOR FDAETAL Hu hft Permnent mgnets () urfe-ounted () Emedded () Inserted Figure 6 Rotor gnets Cross-etions 2.4 Opertionl otor Theory otor opertion is sed on the ttrtion or repulsion etween mgneti poles. sing the three-phse motor shown in Figure 7, the proess strts when urrent flows through one of the three sttor windings nd genertes mgneti pole tht ttrts the losest permnent mgnet of the opposite pole. The rotor will move if the urrent shifts to n djent winding. equentilly hrging eh winding will use the rotor to follow in rotting field. The torque in this exmple depends on the urrent mplitude nd the numer of turns on the sttor windings, the strength nd the size of the permnent mgnets, the ir gp etween the rotor nd the windings, nd the length of the rotting rm. A1 gnet r A1 A1 B2 C1 C2 Rotting mgneti field B1 B2 C1 C2 B1 B2 C1 C2 B1 A2 A2 A2 Figure 7 otor Rottion 3. OTOR ARIETIE There re multiple vrieties of eletri motor differentited y struture nd signl type, ut re generlly sed on the sme priniple s the three-phse motor previously disussed. Figure 8 [2] digrms the different motors orgnized y lssifying fetures. A047 Rev /7/2014 P Proprietry Informtion. Ptent Proteted. nuthorized Photoopy nd Duplition Prohiited P. All Rights Reserved.

9 A047 BRHLE DC OTOR FDAETAL eries Compound hunt ound Field P Homopolr Commuttor DC Eletri otors AC Asynhronous ynhronous Indution inusoidl Brushless DC tepper Hysteresis Relutne Polyphse ingle Phse Figure 8 otor Clssifition The primry differene etween AC nd DC motors is the power type pplied to the rmture. From this vntge, BLDC motor tully is n AC motor. The differene etween n synhronous nd synhronous motor is whether or not the rotor runs t the sme frequeny s the sttor. Eh motor fvors speifi pplitions. Figure 9 illustrtes some of the more populr motor designs. 3.1 Introdution to rious otor Types. Brushed DC otor A rushed DC motor onsists of ommuttor nd rushes tht onvert DC urrent in n rmture oil to n AC urrent, s shown in Figure 9(). As urrent flows through the ommuttor through the rmture windings, the eletromgneti field repels the nery mgnets with the sme polrity, nd uses the winging to turn to the ttrting mgnets of opposite polrity. As the rmture turns, the ommuttor reverses the urrent in the rmture oil to repel the nery mgnets, thus using the motor to ontinuously turn. The ft tht this motor n e driven y DC voltges nd urrents mkes it very ttrtive for low ost pplitions. However, the ring produed y the rmture oils on the rush-ommuttor surfe genertes het, wer, nd EI, nd is mjor drwk.. Brushless DC (BLDC) otor A BLDC motor omplishes ommuttion eletronilly using rotor position feedk to determine when to swith the urrent. The struture is shown in Figure 9(). Feedk usully entils n tthed Hll sensor or rotry enoder. The sttor windings work in onjuntion with permnent mgnets on the rotor to generte nerly uniform flux density in the ir gp. This permits the sttor oils to e driven y onstnt DC voltge (hene the nme rushless DC), whih simply swithes from one sttor oil to the next to generte n AC voltge wveform with trpezoidl shpe. A047 Rev /7/2014 P Proprietry Informtion. Ptent Proteted. nuthorized Photoopy nd Duplition Prohiited P. All Rights Reserved.

10 A047 BRHLE DC OTOR FDAETAL. AC Indution otor (ACI) A sinusoidl AC urrent runs through the sttor to rete rotting vrile mgneti field tht indues urrent in the rotor (typilly mde of non-ferrous mterils). This indued urrent irultes in the rs of the rotor to generte mgneti field. These two mgneti fields run t different frequenies (usully ω -s >ω -r for the motor) nd to generte torque. Figure 9() shows the motor struture. d. Permnent gnet ynhronous otor (P) The P motor shres some similrities with the BLDC motor, ut is driven y sinusoidl signl to hieve lower torque ripple. The sinusoidl distriution of the multi-phse sttor windings genertes sinusoidl flux density in the ir gp tht is different from BLDC motor s trpezoidl flux density. However, newer designs n hieve this sinusoidl flux density with onentrted sttor windings nd modified rotor struture. Rotor mgnet position n signifintly lter the eletril properties of P; ounting the rotor mgnets on the surfe s shown in Figure 6() results in lower torque ripple, while urying the mgnets inside the rotor struture s shown in Figure 6() inreses slieny, whih inreses the relutne torque of the motor. The struture of P is shown in Figure 9(d). e. tepper otor & withed Relutne (R) otor Both stepper motors nd R motors hve similr physil strutures; The sttor onsists of onentrted winding oils while the rotor is mde of soft iron lmintes without oils. It hs douly slient struture (teeth on oth the rotor nd sttor) s shown in Figure 9(e). tepper motors re designed to reple more expensive servo motors. hen the urrent swithes from one set of sttor oils to the next, the mgneti ttrtion etween rotor nd sttor teeth indues enough torque to rotte the rotor to the next stle position, or "step." The rottion speed is determined y the frequeny of the urrent pulse, nd the rottionl distne is determined y the numer of pulses. ine eh step results in smll displement, stepper motor is typilly limited to low-speed position-ontrol pplitions. There is no retive torque (mgnet to mgnet) in n R motor euse the rotor nnot generte its own mgneti field. Insted, oth rotor nd sttor poles hve protrusions so tht the flux length is funtion of ngulr position, whih gives rise to slieny torque. This is the only torque-produing mehnism in n R motor, whih tends to result in high torque ripple. However, due to their simple design, R motor is very eonomil to uild, nd is perhps the most roust motor ville. A047 Rev /7/2014 P Proprietry Informtion. Ptent Proteted. nuthorized Photoopy nd Duplition Prohiited P. All Rights Reserved.

11 A047 BRHLE DC OTOR FDAETAL 1 3 Brushes OT1 OT2 Commuttor 2 4 () Brushed DC motor () Brushless DC (BLDC) motor? -s? -r lip AC Three phse AC power AC Three phse AC power () AC indution motor (ACI) (d) Permnent mgnet synhronous motor (P) tepper motor ontrol Lminted rotor R motor ontrol Phse winding (e) tepper motor & withed relutne (R) motor Figure 9 trutures of Different Types of otors A047 Rev /7/2014 P Proprietry Informtion. Ptent Proteted. nuthorized Photoopy nd Duplition Prohiited P. All Rights Reserved.

12 A047 BRHLE DC OTOR FDAETAL 3.2 Comprison of rious otor Types The BLDC motor hs severl dvntges over other motors. Tle 1 nd Tle 2 summrize the dvntges of the BLDC motor when ompred ginst rushed DC motor nd n AC indution motor. [1][3] Tle 1 Comprison etween BLDC motor nd rushed DC motor Feture BLDC otor Brushed DC otor Atul Advntge Commuttion Eletroni ommuttion sed on rotor position informtion ehnil rushes nd ommuttor Eletroni swithes reple the mehnil devies Effiieny High oderte oltge drop on eletroni devie is smller thn tht on rushes intenne Little/one Periodi o rushes/ommuttor mintenne. Therml performne Output Power/ Frme ize (Rtio) peed/torque Chrteristis Dynmi Response Better High Poor oderte/low Only the rmture windings generte het, whih is the sttor nd is onneted to the outside se of the BLDC.;The se dissiptes het etter thn rotor loted inside of rushed DC motor. odern permnent mgnet nd no rotor losses. Flt odertely flt o rush frition to redue useful torque. Fst low peed Rnge High Low Eletri oise Low High Lower rotor inerti euse of permnent mgnets. o mehnil limittion imposed y rushes or ommuttor o rs from rushes to generte noise, using EI prolems. Lifetime Long hort o rushes nd ommuttor Tle 2 Comprison etween BLDC otor nd AC Indution otor Feture BLDC motor AC indution motor Atul Advntge peed/torque Chrteristis Output Power/ Frme ize (Rtio) Flt High onliner lower torque t lower speeds oderte Dynmi Response Fst Low lip Between ttor And Rotor Frequeny o Yes; rotor runs t lower frequeny thn sttor y slip frequeny nd slip inreses with lod on the motor Permnent mgnet design with rotor position feedk gives BLDC higher strting nd low-speed torque Both sttor nd rotor hve windings for indution motor Lower rotor inerti euse of permnent mgnet BLDC is synhronous motor, indution motor is n synhronous motor A047 Rev /7/2014 P Proprietry Informtion. Ptent Proteted. nuthorized Photoopy nd Duplition Prohiited P. All Rights Reserved.

13 A047 BRHLE DC OTOR FDAETAL The primry disdvntge of BLDC is ost, though this is no inherent reson due to the motor itself; the onstrution of BLDC motor is tully simpler thn tht of rushed DC motor or AC indution motor. The higher ost of BLDC motor is used y the dditionl driver iruit for BLDC motor. However if the pplition requires djustle speed, urte position ontrol, or requires driver iruit, then BLDC motor is not only dvntgeous ut lso less expensive overll. 4. BRHLE DC OTOR COTROL 4.1 with Configurtion nd P Brushless DC motors use eletri swithes to relize urrent ommuttion, nd thus ontinuously rotte the motor. These eletri swithes re usully onneted in n H-ridge struture for single-phse BLDC motor, nd three-phse ridge struture for three-phse BLDC motor shown in Figure 10. sully the high-side swithes re ontrolled using pulse-width modultion (P), whih onverts DC voltge into modulted voltge, whih esily nd effiiently limits the strtup urrent, ontrol speed nd torque. Generlly, rising the swithing frequeny inreses P losses, though lowering the swithing frequeny limits the system s ndwidth nd n rise the ripple urrent pulses to the points where they eome destrutive or shut down the BLDC motor driver. [4] ingle-phse 1 3 Brushless DC otor OT1 OT Three-phse Brushless DC otor () H-ridge () Three-phse ridge Figure 10 Eletri driver iruit 4.2 Eletronis Commuttion Priniple. ingle-phse BLDC otor BLDC ommuttion relies on feedk on the rotor position to deide when to energize the orresponding swithes to generte the iggest torque. The esiest wy to urtely detet position is to use position sensor. The most populr position sensor devie is Hll sensor. ost BLDC motors hve Hll sensors emedded into the sttor on the non-driving end of the motor. Figure 11 shows the ommuttion sequene of single-phse BLDC motor driver iruit. The permnent mgnets form the rotor nd re loted inside the sttor. A Hll position sensor ( ) is mounted to the outside sttor, whih indues n output voltge proportionl to the mgneti intensity (ssume the sensor goes HIGH when the rotor s orth Pole psses y, nd goes LO when the rotor s outh Pole psses y). 1 nd 4 turn on when Hll sensor output is HIGH, s shown in Figure 11() nd (). At this stge, rmture urrent flows through the sttor windings from OT1 to OT2 nd indues the lternte sttor eletromgneti poles ordingly. The mgneti fore generted y rotor mgneti field nd sttor eletromgneti field uses the rotor to rotte. After the rotor signl rehes 180, the Hll output voltge reverses due to its proximity to outh Pole. 2 nd 3 then turn on with urrent reversing from OT2 to OT1, s shown in Figure 11() nd (d). The opposite sttor mgneti poles indue the rotor to ontinue rotting in the sme diretion. A047 Rev /7/2014 P Proprietry Informtion. Ptent Proteted. nuthorized Photoopy nd Duplition Prohiited P. All Rights Reserved.

14 A047 BRHLE DC OTOR FDAETAL Figure 12 shows n exmple of Hll sensor signls with respet to swith drive signls nd rmture urrent. [5] The rmture urrent exhiits sw tooth wveform due to P ontrol. The pplied voltge, swithing frequeny, nd the P duty yle re three key prmeters to determine the speed nd the torque of the motor. ttor OT1 Rotor OT1 1 i 3 1 i 3 OT1 OT2 OT1 OT2 OT2 2 4 OT2 2 4 () Hll sensor vlue: =1 () Hll sensor vlue: =1 (from 0) OT1 OT1 1 i 3 1 i 3 OT1 OT2 OT1 OT2 OT2 2 4 OT2 2 4 ()Hll sensor vlue: =0 (from 1) (d) Hll sensor vlue: =0 Figure 11 ingle-phse BLDC otor Commuttion equene A047 Rev /7/2014 P Proprietry Informtion. Ptent Proteted. nuthorized Photoopy nd Duplition Prohiited P. All Rights Reserved.

15 A047 BRHLE DC OTOR FDAETAL Hll I OT1-2 0 Figure 12 ingle-phse BLDC otor ensor versus Drive Timing. Three-Phse BLDC otor A three-phse BLDC motor requires three Hll sensors to detet the rotor s position. Bsed on the physil position of the Hll sensors, there re two types of output: 60 phse shift nd 120 phse shift. Comining these three Hll sensor signls n determine the ext ommuntion sequene. Figure 13 shows the ommuttion sequene of three-phse BLDC motor driver iruit for ounterlokwise rottion. Three Hll sensors,, nd re mounted on the sttor t 120 intervls, while the three phse windings re in str formtion. For every 60 rottion, one of the Hll sensors hnges its stte; it tkes six steps to omplete whole eletril yle. In synhronous mode, the phse urrent swithing updtes every 60. For eh step, there is one motor terminl driven high, nother motor terminl driven low, with the third one left floting. Individul drive ontrols for the high nd low drivers permit high drive, low drive, nd floting drive t eh motor terminl. However, one signl yle my not orrespond to omplete mehnil revolution. The numer of signl yles to omplete mehnil rottion is determined y the numer of rotor pole pirs. Every rotor pole pir requires one signl yle in one mehnil rottion. o, the numer of signl yles is equl to the rotor pole pirs. A047 Rev /7/2014 P Proprietry Informtion. Ptent Proteted. nuthorized Photoopy nd Duplition Prohiited P. All Rights Reserved.

16 A047 BRHLE DC OTOR FDAETAL Hll sensor vlue: =001 Hll sensor vlue: = Hll sensor vlue: =101 Hll sensor vlue: = Hll sensor vlue: =100 Hll sensor vlue: =110 Figure 13 Three-Phse BLDC otor Commuttion equene Figure 14 shows the timing digrms where the phse windings,, nd re either energized or floted sed on the Hll sensor signls,, nd. This is n exmple of Hll sensor signl hving 120 phse shift with respet to eh other, where the motor rottes ounter-lokwise. Produing Hll signl with 60 phse shift or rotting the motor lokwise requires different timing sequene. To vry the rottion speed, use pulse width modultion signls on the swithes t muh higher frequeny thn the motor rottion frequeny. Generlly, the P frequeny should e t lest 10 times higher thn the mximum motor rottion frequeny. Another dvntge of P is tht if the DC us voltge is muh higher thn the motor-rted voltge, so limiting the duty yle of P to meet the motor rted voltge ontrols the motor. A047 Rev /7/2014 P Proprietry Informtion. Ptent Proteted. nuthorized Photoopy nd Duplition Prohiited P. All Rights Reserved.

17 A047 BRHLE DC OTOR FDAETAL Hll ensor Code Eletril yle Eletril yle One mehnil rottion 001 High Flot Low High Flot Low High Flot Low Figure 14 Three-phse BLDC motor sensor versus drive timing. ensorless BLDC otor Control However, sensors nnot e used in pplitions where the rotor is in losed housing nd requires miniml eletril entries, suh s ompressor or pplitions where the motor is immersed in liquid. Therefore, the BLDC sensorless driver monitors the BEF signls insted of the position deteted y Hll sensors to ommutte the signl. The reltionship etween the sensors output nd the BEF is shown in Figure 15. The sensor signl hnges stte when the voltge polrity of the BEF rosses from positive to negtive or from negtive to positive. The BEF zero-rossings provides preise position dt for ommuttion. [6] However, s BEF is proportionl to the speed of rottion, this implies tht the motor requires minimum speed for preise feedk. o under very low speed onditions suh s strt-up dditionl detetors suh s open loop or BEF mplifiers re required to ontrol the motor (This is eyond the sope of this pplition note). The sensorless ommuttion n simplify the motor struture nd lower the motor ost. Applitions in dusty or oily environments tht require only osionl lening, or where the motor is generlly inessile, enefit from sensorless ommuntion. A047 Rev /7/2014 P Proprietry Informtion. Ptent Proteted. nuthorized Photoopy nd Duplition Prohiited P. All Rights Reserved.

18 A047 BRHLE DC OTOR FDAETAL BEF Hll ensor Code Eletril yle Eletril yle One mehnil rottion Figure 15 Hll ensor versus BEF 5. ARY This pplition note introdues the motor fundmentls, with speil ttention to BLDC motors.. As desried in this doument, BLDC motor hs mny dvntges over rushed DC motor nd n AC indution motor: It is esily ontrolled with position feedk sensors nd generlly performs well, espeilly in speed/torque. ith these dvntges, BLDC motor will spred to more pplitions. oreover, with the development of sensorless tehnology, BLDC motor will eome onvenient or indispensle in pplitions with environmentl limittions. A047 Rev /7/2014 P Proprietry Informtion. Ptent Proteted. nuthorized Photoopy nd Duplition Prohiited P. All Rights Reserved.

19 A047 BRHLE DC OTOR FDAETAL REFERECE: [1]. uhmmd ueen, Brushless DC otor Primer, otion Teh Trends, July, [2]. Derek Liu, Brushless DC otors de Esy, Freesle, [3]. Pdmrj Yedmle, Hnds-on orkshop: otor Control Prt 4 -Brushless DC (BLDC) otor Fundmentls, irohip A885, [4]. m Roinson, Drive nd Control Eletronis Enhne the Brushless otor s Advntges, Apex, [5]. Domenio Arrigo, L6234 Three Phse otor Driver, T A1088, [6]. ensorless BLDC otor Control nd BEF mpling ethods with T7C, T A1946, July, OTICE: The informtion in this doument is sujet to hnge without notie. sers should wrrnt nd gurntee tht third prty Intelletul Property rights re not infringed upon when integrting P produts into ny pplition. P will not ssume ny legl responsiility for ny sid pplitions. A047 Rev /7/2014 P Proprietry Informtion. Ptent Proteted. nuthorized Photoopy nd Duplition Prohiited P. All Rights Reserved.