Development of Brushless DC Motor with low cogging torque for Ceiling Fan

Transcription

1 PEDS29 Developmen of Brushless DC Moor wih low cogging orque for Ceiling Fan Chuan-Sheng Liu Member, IEEE Naional Formosa Universiy Dep. of Aeronauical Engineering 632 Yunlin, Taiwan Absrac -- The improvemens of he new srucure of a brushless DC (BLDC moor wih he low cogging orque for he ceiling fan is presened. The new ype ceiling fan is designed by using BLDC moor heory and he six-sep wave form for he purpose of he manufacure cos reducion. The energy also can be saved a leas 5% when he new ype moor is compared o he convenional fan based on he inducion moor. The cogging orque also can be improvemen by using he sin back EMF volage wih he sine wave form currens. The new BLDC moor is required o mee boh of he basic ceiling fan conrol and he cos reducion. Index Terms-- ceiling fan, brushless DC (BLDC moor, speed conroller, hall sensor, cogging orque. I. INTRODUCTION The convenional ceiling fan based on he inducion moor is popular. Those spli-phase inducion moor are exernal roor machines wih large diameer and large size. They are usually low-cos machines and operaed a high slip, herefore, he ceiling fan have poor performance. The performance of he exernal-roor spli-phase inducion moor has been improved by using he 2-D finie elemen analysis []. However, he pulsaing orque and efficien of he fan is sill a problem. For he energy conservaion reason, he developmen and commercializaion of high efficiency elecric moor is required for he ceiling fan. The high efficiency elecric moor drivers sysem can replace he ceiling fan which is base on he inducion moor. In order o reduce he consumpion of he elecric energy, he brushless dc (BLDC moor wih high efficiency can be a good moor for he ceiling fan [2]. The BLDC moor also has many advanages like high efficiency, compac volume and less noise. In his paper, he new ype ceiling fan is firs designed by using he BLDC moor heory [3-6] and he six-sep wave form for he purpose of he manufacure cos reducion. The energy will be saved when he new ype moor is compared o he convenional inducion moor fan. However, he roaion noise of he BLDC moor is limied when he ceiling fan is operaing in he house. The new BLDC moor wih he low cogging orque is also required o mee boh of he basic ceiling fan conrol and he cos reducion. II. Jonq-Chin Hwang Naional Taiwan Universiy of Science and Technology Dep. of elecrical engineering jchwang@mouse.ee.nus.edu.w THE MOTOR DESIGN AND DRIVERS SYSTEM A. he moor design The basic requiremen of he BLDC moor of he ceiling fan is limied under he commercializaion. The operaing condiion of he BLDC moor is lised as follow: inpu power : AC source V or 22V speed range : 9 rpm o 2 rpm speed change: a leas 3 sep( rpm for low speed. 6rmp for mid speed, and 2 rpm for hi speed The new BLDC moor and he flux analysis is designed as an exernal-roor moor wih 8 poles and 2 slos shown as in fig.. There are 2 single layer coils on he 2 slos for he reducion of he assembly line. The inverer will provide he 3 phase curren on hose coils, hen he fan moor has he roaing orque. Fig.. moor cross secion (8 poles, 2slos, he saor is inernal o roor and each slo will conain single layer winding. The roor conains he number of 8 poles. B. he drivers sysems The new srucure of he drivers sysems for he speed conroller of he ceiling fan is shown in fig.2. According o he roor posiion deeced by hall sensors, he conroller cener, Digial Signal Processor (DSP, will give he speed command o he DC-AC inverer, hen hree phase volage supplied by he inverer will applied o hree phase coils and be obained he hree currens. 778

2 PEDS29 Fig.2. he drivers sysem of ceiling fan The DC elecric power, 24 DC volages, is obained hrough he AC-DC converer from he V or he 22V inpu AC power. The fly-back converer wih he advanages such as cos effecive, isolaion, and small size is seleced. The speed conrol loop of he closed loop is shown in fig.3. Fig.4. he 3 phase power circuis of he moor and drivers sysem The 3 phase volages are: d v = Rsi + Ls i + e d ( Fig.3. Speed conrol loops of he closed loop The new BLDC moor is required o mee boh of he basic ceiling fan conrol and he cos reducion. The orque of he fan moor is consan as he fan is running in fixed speed. The BLDC moor can be allowed o operae in he open-loop conrol for saving he cos of he curren sensor. The accuracy of he fan speed is no asked o be accurae, hen he BLDC moor can be used he six-sep square wave conroller or he sensor-less commuaion mehods [3-5]. The propery of he new BLDC fan moor and he drivers sysem fis he commercializaion, he cos effec, he consumpion of he elecric energy, he small size, he less noise, and easy he assembly line. III. THE BLDC SERVO MOTOR THEORY AND THE CONTROLLER The new BLDC fan moor is design an exernal roor moor wih 8 poles and 2 slos. The 3 phase currens in he 2 coils, assumed o be balance, provide he orque of he fan moor. Assuming ha he damping winding effec and he sauraion is negleced, he 3 phase power circuis of he moor and drivers sysem is shown in fig.4. Where v = i = i R s = diag L s = diag e = e [ v v v ] a b [ i i ] a b c [ RsRsRs [ Ls Ls Ls ] ] [ e e ] a b c c The roor posiion deeced by 3 hall sensors is divided ino he six seps in each cycle of he line volages. Fig.5. shows ha he relaionship beween he hall sensor and he line volages. (a 3ω r 3ω r (b (c (d H a H b H c e ab ebc eca F F 2 F 3 F 4 F 5 F6 Fig.5. he hall sensor posiion and he line volages According o each sep, 6 elecrical degree, he DSP conroller will give he commuaion command o he swich such as Ta +, Tb +, Tc +, Ta -, Tb -,and Tc -. The ideal phase 779

3 PEDS29 currens in he 3 phase coils are shown in fig.6 and provide he orque. 3ω r e ab ebc eca (a 3ω r i a (b (c (d i b i c F F 2 F 3 F 4 F 5 F6 Fig.6. The ideal phase currens and he line volages Assuming ha he inducance in he coils is consan, he average orque is lised as N p T ~ e 2 λ mi pm 2 (2 Where is he flux linkage. N p is he number of poles. I pm is he phase curren. IV. TEST RESULTS A. The convenional ceiling fan The convenional ceiling fan based on spli-phase inducion moor is lised under he single phase power supply V or 22V. The consumpion of he elecric power corresponding o 3 seps speed conrol is lised in he able. Fig.7. he inpu volage (golden line:v/div and inpu curren (Blue line:.2a/div operaing in hi-speed conrol B. The new BLDC fan moor The new BLDC fan moor is design an exernal roor moor. The picure of he moor wih he driver circui is shown in fig.8. Fig.8. The picure of he moor wih he driver circui The consumpion of he elecric power is concerned. The roaion speed of he BLDC moor is adjused o be hose of he convenional ceiling fan. The able 2 shows he inpu power corresponding o he 3 fixed roaion speeds. The able 3 and he fig.9. shows he compare of he inpu power beween wo moors. During any of he operaion speed, he energy saving of he new BLDC moor is abou 5%. However, he power facor correcion is also required o improve he power facor. Table :The es resul of he convenional ceiling fan speed Speed (rpm Power (W PF ( cos θ Vol (V Curren (A Low Mid Hi Table 2: The es resuls of he BLDC moor speed Speed (rpm Power (W PF (cosθ Vol (V Curren (A Low mid hi During he hi-speed operaion, he consumpion power wih he uni power facor (PF is abou 65W show as in fig.7. When he fan operaes in mid-speed, he curren is leading he inpu volage 3 degree. This shows ha he good produc of he convenion ceiling fan has a good power facor. Fig.9. he energy saving of he new BLDC moor is abou 5%. 78

4 PEDS29 The orque of he ceiling fan is almos consan, when he fan is operaing in fixed speed. Operaing in he hi-speed, he currens, shown in fig.., are similar o hose ideal currens. Fig.2. Three Phase Volages for he BLDC moor Fig.. currens wave form (ia, ib, ic (A/div and line volage Vab (4V/div of he moor, operaing in he hi-speed. Fig.3. Three Phase Volages for he new BLDC moor Fig.. he phase curren ia(blue:2a/div and hose conrol signals such as Ha (green:5v/div Vgs (pink: 2V/div Vds (golden: 2V/div. Fig. shows ha he relaion ship beween he conrol signals such as he hall sensor (Ha, Vgs of he MOSFET, Vds of he MOSFET, and phase currens ( i a. The above wave form of currens fis o hose in he heory. The cogging orque also can be improvemen by using he sin back EMF volage wih he sine wave form currens [6-9]. Fig. 2 and Fig.3 show he hree Phase Volages for he wo ypes of BLDC moors. The former shows he phase volage wih 3 rd harmonics which will lead o he noise of he roaion, and he laer shows he improvemen model wih he sin wave phase volage and he noise reducion by working wih he sin wave curren. Fig.4 shows ha he moor s cogging orque hen can be improvemen and he noise also be reduced. The moor have anoher benefi wih he lower harmonics of he inpu curren. Fig.4. he cogging orque of BLDC ceiling fan (a and he new BLDC (b is improvemen V. CONCLUSIONS For he energy conservaion, he new BLDC moor is designed as an exernal-roor moor wih 8 poles and 2 slos for he ceiling fan. The energy can be saved a leas 5%, when he new ype moor is compared o he convenional fan based on he inducion moor. The cogging orque also can be improvemen by using he sin back EMF volage wih he sine wave form currens. The new BLDC moor mees boh of he basic requiremen of he fan speed conrol and he cos reducion. The price of he new fan, abou 5 us dollars, is cos effecive. 78

5 PEDS29 ACKNOWLEDGMENT This work was sponsored by he Naional Science Council, Taiwan, R. O. C., Projec number E-5-49-CC3. REFERENCES [] Holik, P. J. Dorrel, and D. G. Popescu, M., Performance Improvemen of an Exernal-Roor Spli-Phase Indcion Moor for Low-Cos Drive Applicaions Using Exernal Roor Can, IEEE Transacions on Magneics, vol. 43, pp , june 27. [2] Rajagopal, K.R.; Sahaiah, C.; Compuer Aided Design and FE Analysis of a PM BLDG Hub Moor, Power Elecroncis, Drives and Energ Sysem, 26 PEDES Inernaional Conference,2-5 Dec. 26, pp-6. [3] Cheng-Hu Chen, Ming-Yang cheng, A New Cos Effecive Sensorless Commuaion Mehod for Brushless DC Moors Wihou Phase Shif Circui and Neural Volage, IEEE Tran. On P.E., Vol. 22, No2, Mar.27. [4] Q. Jiang, C. Bi and R. Huang, A new phase-delay mehod o deec back EMF zero-crossing poins for sensorless conrol of spindle moor, IEEE Tran. on Magneic, Vol.4, No.7, pp228, july. 25. [5] Tae-Hyung Kim, Ehsani, M, An error analysis of he sensorless posiion esimaion for BLDC moors, R. Nicole, Indusry Applicaions Conference, 23, 38 h, IAS Annual Meeing, Vol,, pp6-67, 2-6 Oc. 23. [6] C. C. Hwang and Y. H. Cho, Effecs of leakage flux on magneic fields of inerior permanen magne synchronous moors, IEEE Tran. on Magneics, vol. 37, pp , 2. [7] T. F. Chan and Lie-Tong Yan, Analysis and performance of a surfacemouned NdFeB permanen-magne a.c. generaor. Inernaional Conference, Advances in Power Sysem Conrol, Operaion and Managemen, vol. 2, pp.-4,997 [8] T. F. Chan and Lie-Tong Yan, Analysis and performance of a hreephase a.c. generaor wih inse permanen-magne roor. Inernaional Conference, Advances in Power Sysem Conrol, Operaion and Managemen, vol. 2, pp ,2. [9] Y. Honda, T. Nakamura, T. Higaki and Y. Takeda, Moor design consideraions and es resuls of an inerior permanen magne synchronous moor for elecric vehicles, Thiry-Second IAS Annual Meeing Conference, vol., pp.75-82,