Download Data Debugging in Power System Operations Using Gap Statistic A

第十二屆台灣電力電子研討會暨展覽會
台灣 台南市 102 年 11 月 02 日
Development of a Switched-Reluctance Motor Driven Cooling Fan
開關式磁阻馬達驅動散熱風扇之開發
1
林益慰
Y. C. Lin
1
周科甫
1
葉名哲
K. F. Chou M. J. Yeh
2
2
王建昌
2
余守龍
楊錞忠
C. C. Wang S. L. Yu
國立清華大學電機系
台灣 新竹市
Department of Electrical Engineering
National Tsing Hua University
Hsinchu, Taiwan, ROC.
[email protected]
1
2
張鈺炯
1
廖聰明
C. C. Yang Y. C. Chang C. M. Liaw
工研院綠能與環境研究所
台灣 新竹市
Green Energy and Environment Research Laboratory
Industrial Technology Research Institute
Hsinchu, Taiwan, ROC.
[email protected]
2
摘 要
driver with wide varying speed range, a high cost inverter
is indispensable.
Compared with other commonly used motors, switched
reluctance motor [3-5] possesses many merits, such as
simple and rigid structure, high generating torque and
acceleration capabilities, suitable for high speed operation,
simple drive circuit and switching control. In particular, its
rotor is not equipped with conductors or permanent
magnets, this makes it have no cogging torque and thus
easy to start. During the past years, SRM has been
gradually employed in some plants, such as home
appliances, air-conditioners, and fans [3-11].
However, some inherent disadvantages may limit the
application competitive capability of SRM. The nonlinear
winding inductance and developed torque characteristics
make the SRM drive be difficult to achieve high driving
performance. The major issues in establishing a highperformance SRM drive include: (i) Motor design: The
researches concerning SRM motor design can be referred
to [12-18]. (ii) proper converter [19-24]: Miller converter
and asymmetric converter are two typical ones. The former
is the simplest schematic, but it is inherently not suited for
high speed operation. As to the latter, it has the largest
PWM switching flexibility subject to having higher cost.
These two converters are employed to power the developed
SRM fan and comparatively evaluated. For SRMs with
even phase number, one can adopt the modified Miller
converter to have the best compromised circuit and
switching control characteristics. Other special functions
possessed by some specific converters include stored
energy recovery, DC-link voltage boosting, power factor
correction and soft-switching, etc. (iii) Switching control:
the SRM converter switching control approaches can
broadly be classified into current-mode control and direct
duty-ratio voltage-mode control. The latter is simpler, but it
has worse winding current and driving performances. More
importantly, it is not suited for the applications requiring
higher performance and speed. However, it is still
applicable for a SRM driven fan if proper commutation is
set. (iv) Commutation instant shift [25]: This can reduce
the effects of back-EMF, and thus the improved winding
current and developed torque characteristics under high
speeds. (v) Other affairs include voltage boosting, ripple
torque reduction, vibration reduction [26], …, etc.
As the rotor speed increases, the increased back
electromagnetic force (EMF) will let the motor winding
current become sluggish. Although commutation advanced
本文旨在介紹開關式磁阻馬達驅動散熱風扇之設計、製作
及驅動控制。首先，在探究開關式磁阻馬達之結構特徵後，設
計製作一部70W三相6/4之馬達，並配裝其風扇負載，以及從
事其關鍵參數之估測，以利於驅動系統之分析與設計。接著建
構一密勒轉換器及一非對稱橋式轉換器，以及其切換控制機構
與換相時刻調控機構。其次，實測評定兩型轉換器供電開關式
磁阻馬達驅控風扇之比較特性，以及其與直流無刷馬達驅動風
扇之性能比較評估。最後建構一返馳式切換整流器，並評估具
切換式整流器前級SRM驅動散熱風扇系統之總體操控性能。
關鍵詞：開關式磁阻馬達、馬達設計、散熱風扇、轉換器、脈
寬調變、換相調控、切換式整流器、返馳式。
Abstract
This paper presents the design, implementation and driving
control of a switched-reluctance motor (SRM) driven cooling fan.
First, after exploring the motor structural features, a 70W
three-phase SRM with 8/6 teeth is designed and manufactured.
Meanwhile, the cooling fan is coupled to the motor shaft to serve
as its mechanical load. The SRM key parameters are estimated
and employed for making its drive system analysis and design.
Then, a Miller converter and a asymmetric bridge converter are
constructed with their switching and commutation shift schemes
being properly designed. Thorough experimental evaluations are
conducted for the SRM driven fan powered by different
converters. Further comparative performance assessment is also
made between the developed SRM driven fan and an available
brushless DC motor (BDCM) fan with the same blade. Finally, a
flyback switch-mode rectifier (SMR) is developed and used to
establish well-regulated DC-link voltage of the SRM converter.
Experimental results indicate that good driving performance and
line drawn power quality of the whole SMR-fed SRM driven fan
are obtained.
Keywords: switched-reluctance motor, motor design, cooling fan,
converter, PWM, commutation shift, switch-mode rectifier,
flyback.
I. INTRODUCTION
As generally recognized, the drawn power of a motor
driven fan, pump, or compressor is proportional to the
cubic of speed, i.e., P  TLr  r3 [1,2]. Hence, a variable
speed motor driven fan may possess great energy saving
potential. Traditionally, the small cooling fan is driven
using single-phase induction motor with limited variable
speed range and low efficiency. The brushless DC motor
(BDCM) driven fan can possess improved performance and
efficiency subject to the increased cost. For an a motor
1
第十二屆台灣電力電子研討會暨展覽會
台灣 台南市 102 年 11 月 02 日
where  r  rotor angular position, r  rotor angular
speed,  ( r , i ) winding flux linkage, e ( r , i, r )  back
electromagnetic force (EMF), Rs  winding resistance and
L(r , i )  winding inductance. The winding resistances and
inductances can be measured by making locked-rotor test at
various rotor positions under different frequencies and
current levels.
The phase developed torque Tei and the composite
developed torque Te can be derived from the filed energy
or co-energy as:
shift may possess some extent of equivalent fieldweakening effect, its effectiveness is limited in higher
running speeds. In this case, the voltage boosting must be
adopted instead. For a motor drive powered by mains, one
can apply SMR [27] as a front-end AC/DC converter to
accomplish this task. Meanwhile, good line drawn power
quality can be obtained simultaneously. Till now, there
were a lot of SMRs, the surveys for single-phase SMRs can
be found in [28,29]. Among these, the boost type SMR
[27-31] possess the most flexible PFC control ability and
the best performance. However, its DC output voltage must
be larger than the peak input voltage. For the applications
requiring galvanic isolation, one can adopt the flyback
SMR [28,29,32] subject to having lower power rating. In
the developed low power SRM driven fan, the flyback
SMR is adopted to serve as the front-end AC/DC converter.
The design, implementation and driving control of a
SRM driven cooling fan are presented in this paper. A
three-phase 70W, 900rpm, 8/6 SRM is designed and
manufactured, and the test cooling fan blade is coupled to
its shaft. The designed SRM key parameters are estimated
for assessing its basic characteristics. Then, a Miller
converter and a asymmetric bridge converter fed SRM fans
are established. Their comparative driving performances
are evaluated experimentally. In addition, the performance
of the developed SRM fan is also compared to an available
brushless DC motor (BDCM) fan with the same blade.
Finally, a SMR-fed SRM fan is developed, and its good
driving performance and line drawn power quality are
verified experimentally.
Tei 
L ( , i ) 
 1 i r i ii2  kti ii2 ,
 r
2
 r
Wc,i
i=1,2,…, N (2)
N
N
dr
Te   Tei  1  kti ii2  TL  Br  J
2 i 1
dt
i 1
(3)
where kti ( r , ii ) denotes a torque generating constant, N =
phase number, TL  load torque, B  total coefficient of
friction, J  total moment of inertia. From (2) and (3) one
can be aware that SRM has the back-EMF and developed
torque characteristics like those of brush series DC motor.
For a fan load, its load torque can be expressed as:
TL  k Lr2
(4)
where k L is constant depending on the fan blade type.
C. Converters and Switching Control
Till now there have been many SRM converters [19-24].
The selection depending on PWM switching control
flexibility, energy recovery function, operation quadrant,
voltage boosting, …, etc. Asymmetric converter with 2N
switches possesses the largest PWM switching flexibility.
Miller converter is the simplest and most cost-effective
schematic, but it is not suited for high speed operation
owing to the coupling effect during commutation period.
However, if the commutation advanced shift is properly
made, it is still applicable for the applications with limited
speed range. For the SRMs with even phase number, one
can adopt the modified Miller converter to have the best
compromised circuit and switching control characteristics.
In the developed SRM fan, both Miller and Asymmetric
converters are used and comparatively evaluated their
driving characteristics. In addition, a flyback SMR is
constructed and used as the front-end AC/DC converter to
draw power from the mains with satisfactory power quality.
Basically, the switching control approaches of SRM
drive can be categorized as direct duty-ratio control and
current-mode control with their typical winding current
waveforms being sketched in Figs. 1(a) and 1(b).
Obviously, the former is simpler in control scheme subject
to having single-pulse wave shape. The commutation
advanced shift is needed to perform under higher speeds.
However, the care in choosing converter switches should
be made, and it is suited for the applications with very high
operation speeds.
For the SMR drive with direct-duty PWM control, its
control system block diagram can be drawn from (3) as
shown in Fig. 2. Wherein H n (s) denotes a hypothesized
tracking transfer function, which is obviously not ideal, i.e.,
H n (s)  1 . The characteristics are affected by nonlinear
winding inductance, back-EMF, winding current waveform,
load, …, etc. Hence, the suited robust control is needed to
yield better operating performance of a SRM driven plant.
II. SWITCHED-RELUCTANCE MOTOR AND ITS DRIVING
CONTROL
A. Structural Features
SRM possesses the same structure as those of variable
reluctance stepping motor, which belongs to the motor of
doubly-salient/singly-excited with concentrated windings.
However, its stator winding excitation is made according to
the sensed rotor absolute position to yield much better
torque developing capability. Since the SRM is emphasized
on the speed driving applications, it generally has lower
numbers of stator and rotor teeth than those of stepping
motors. The commonly used SRMs are 2-phase 4/2,
3-phase 6/4, 4-phase 8/6, 5-phase 10/8 and 3-phase 12/8.
Generally speaking, the increase of the numbers of phase
number N p , stator tooth number N s and the rotor tooth
number N r can lead to the less torque ripple. However,
the larger phase number leads to the increase of converter
circuit cost, and the increase of reliability in fault tolerance
operation. Considering the typical fan driving performance
and the cost, the developed fan SRM adopts the one with
3-phase 6/4.
B. Physical Modeling
By assuming linear magnetic circuit and neglecting the
coupling between phases, the per-phase voltage equation of
a SRM can be expressed as: [3,4,26]:
d ( r , i )
 ( r , i ) di  ( r , i ) d r
 Rsi 

dt
i
dt
 r
dt
di L( r , i )
 Rsi  L( r , i ) 
i r
dt
 r
di
 Rsi  L( r , i )  e ( r , i, r )
(1)
dt
v  Rsi 
2
第十二屆台灣電力電子研討會暨展覽會
台灣 台南市 102 年 11 月 02 日
Table 1: Specifications of the designed SRM
Np
Ns / Nr
ODstator
ODrotor
Wsp
Betas
Betar
lg
alphas
alphar
-
Fig. 1. Sketched winding currents of a SRM under: (a) direct-duty
PWM control; (b) current-mode PWM control.
Phase number
Stator/rotor teeth
Stator outer diameter [mm]
Rotor outer diameter [mm]
Stator yoke thickness [mm]
Stator pole arc [degree]
Rotor pole arc [degree]
Air-gap length [mm]
Winding (turns per pole)
Conductor diameter [mm]
Rated power [W]
Rated speed [rpm]
Stator pole embrace
Rotor pole embrace
Stator height [mm]
Rotor height [mm]
3
6/4
94
53.3
6
30
36
0.35
588
0.35
72
900
0.5
0.4
30
30
IV. COMPARATIVE PERFORMANCE EVALUATION
A. Miller Converter-fed SRM Fan and BDCM Fan
The power circuit and control scheme of the developed
Miller converter-fed SRM driven fan are shown in Fig. 6.
The switches adopt the power MOSFET 20N60CFD,
20A/600V (Infineon), the diodes employ the power diode
D12S60, 12A/600V (Infineon), and Cdc  780 F / 400V
All control schemes are realized using OP-amplifier based
analog circuits. The commutation signal generator and
commutation instant shift scheme are shown in Fig. 7,
while Fig. 8 is the PWM generator and speed controller.
The measured A-phase S A , Q A and i A of the Miller
converter-fed SRM fan at ( Vdc = 250V ， r = 850rpm)
without (   0  ) and with (   2.9  ) commutation
advanced shift are plotted in Figs. 9(a) and 9(b). The
measured AC input powers Pac under various fan speeds
of the developed Miller converter SRM driven fan and a
BDCM driven fan with the same blade are compared in
Table 2.
Fig. 2. Control block diagram of a SRM drive with direct dutyratio PWM scheme.
III. DESIGN OF A FAN SWITCHED-RELUCTANCE MOTOR
Considering the general fan driving performance
requirement and the cost, the developed fan SRM adopts
the 3-phase having 6/4 teeth. And for making the
comparison, the sizes and ratings are specified the same as
those of a available BDCM fan. Figs. 3(a) and 3(b) show
the photos of these two cooling fans. The structural
configuration and the Hall sensing scheme arrangement of
the designed fan SRM are shown in Fig. 4(a) and Fig. 4(b).
For verifying the correctness of the mounted Hall sensors,
the A-phase winding is fed by an AC voltage source with
60V/1kHz and the SRM is forcibly turned by hand, the
measured rotor position amplitude modulated current i A
and the commutation signal S A are plotted in Fig. 4(c).
The correctness of the mounted Hall position sensors can
be observed from the results.
Table 1 lists the specifications of the designed SRM. The
measured winding inductance profile at different rotor
positions using the LCR-meter (Hioki 3532-50 LCR
HiTESTER) under 100Hz is plotted in Fig. 5. And the
winding resistance is 30.7  .
SA
5V
QA
5V
iA
1.690A
1A
(a)
5ms
SA
5V
QA
5V
iA
1A
(b)
5ms
Fig. 9. Measured A-phase S A , Q A and i A of the developed
Miller converter-fed SRM fan at ( Vdc = 250V， r = 850rpm): (a)
without commutation advanced shift   0  ; (b)   2.9  .
Fig. 3. Photos of a SRM driven fan and a BDCM driven fan.
3
第十二屆台灣電力電子研討會暨展覽會
台灣 台南市 102 年 11 月 02 日
Table 2: Performance comparison between the developed Miller
converter SRM driven fan and a BDCM driven fan
BDCM driven fan
[6]
Miller converter SRM driven fan
r (rpm)
Pac (W)
r (rpm)
Pac (W)
301 rpm
398 rpm
494 rpm
606 rpm
706 rpm
10.76 W
16.56 W
23.21 W
33.18 W
42.85 W
303 rpm
405 rpm
504 rpm
607 rpm
703 rpm
5.034 W
9.885 W
17.32 W
26.73 W
38.49 W
804 rpm
53.97 W
803 rpm
64.55 W
849 rpm
60.14 W
852 rpm
97.80 W
[7]
[8]
36.46 W
(   2.2  )
51.78 W
(   1.44  )
60.38 W
(   2.9  )
[9]
[10]
………………………………………
VI. CONCLUSIONS
This paper has presented the design of a fan SRM, and
the operation performance evaluation of the established
SRM driven cooling fan. A three-phase 70W SRM with 8/6
teeth is designed and manufactured, and the fan blade is
coupled to its shaft to serve as its mechanical load. The
motor winding parameters and Hall sensing signals are
estimated to comprehend the basic characteristics of the
designed motor. In driving control, a Miller converter and a
asymmetric bridge converter are constructed to power the
SRM driven fan, and their driving performances are
comparatively evaluated. Moreover, satisfactory operation
characteristics of the developed SRM fan are also
confirmed from the performance comparison being made
between the developed SRM driven fan and an available
BDCM fan with the same blade. Finally, a front-end
flyback SMR is developed to let the established SMR-fed
SRM driven fan have good line drawn power quality from
the mains.
From the experimental studies made in this paper one
can find that the asymmetric bridge converter can let the
SRM fan yield good winding current waveform and lower
power consumption without applying commutation shift.
For the SRM fan powered by Miller converter, the suited
commutation shift under higher speeds is needed to yield
satisfactory driving performance. The commutation shift
can be conducted via fuzzy tuning or programmed setting
according the fan speed. The development of automatic
commutation shift approach is worth further studying.
[11]
ACKNOWLEDGMENT
[22]
本文承蒙經濟部能源局之能源基金計畫經費支持而完
成相關研究，僅此致謝。
[23]
[12]
[13]
[14]
[15]
[16]
[17]
[18]
[19]
[20]
[21]
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