Parameter Identification of a Synchronous Reluctance Motor by using a Synchronous PI Current Regulator at a Standstill

Transcription

1 Parameter Ientification of a Synchronous Reluctance Motor by using 491 JPE Parameter Ientification of a Synchronous Reluctance Motor by using a Synchronous PI Current Regulator at a Stanstill Seon-Hwan Hwang, Jang-Mok Kim, Huynh Van Khang, an Jin-Woo Ahn School of Electrical Eng., Pusan National University, Busan, Korea Dept. of Electrical Eng., Aalto University, Finlan School of Electrical an Mechatronics Eng., Kyungsung University, Busan, Korea Abstract This paper proposes an estimation algorithm for the electrical parameters of synchronous reluctance motors (SynRMs) by using a synchronous PI current regulator at stanstill. In reality, the electrical parameters are only measure or estimate in limite conitions without fully consiering the effects of the switching evices, connecting wires, an magnetic saturation. As a result, the acquire electrical parameters are ifferent from the real parameters of the motor rive system. In this paper, the effects of switching evices, connecting wires, an the magnetic saturation are consiere by simultaneously using the short pulse an close loop equations of resistance an synchronous inuctances. Therefore, the propose algorithm can be easily an safely implemente with a reuce measuring time. In aition, it oes not nee any external or aitional measurement equipment, information on the motor s imensions, an material characteristics as in the case of FEM. Several experimental results verify the effectiveness of the propose algorithm. Key Wors: Close loop equations, Electrical parameter estimation, Short pulse, Synchronous PI current regulator, Synchronous reluctance motor I. INTRODUCTION Recently, synchronous reluctance motors (SynRMs) have receive a lot of attention because of their high output power, low cost, an enurance in various inustry applications. The saliency rotor has no magnets or winings, so it is mechanically robust for high spee operation an it is suitable for sensorless control [1] [4]. The phase resistance an synchronous inuctances are the basic parameters escribing SynRM behavior. The researchers in [5] showe that the electrical angle of a current vector with respect to the high permeance axis (-axis) is a function of the ratio of the - an q-axis inuctances for some control methos. The performance of the rive system epens on the PI gains of the synchronous PI current regulator an they are calculate from the electrical parameters [6]. Therefore, an exact measurement of the synchronous inuctances is very important to the performance of the motor rive system. For SynRMs, there is a nonlinear relationship between the stator inuctances an the currents ue to magnetic saturation in the - an q-axes, respectively. This causes some problems Manuscript receive Feb. 23, 2010; revise Jul. 14, 2010 Corresponing Author: jmok@pusan.ac.kr Tel: , Fax: , Pusan Nat l Univ. School of Electrical Eng., Pusan Nat l Univ., Korea Dept. of Electrical Eng., Aalto Univ., Finlan School of Electrical an Mechatronics Eng., Kyungsung Univ., Korea for accurate control of the SynRM [7] [9]. It is not easy to measure the exact inuctance parameters of a SynRM while consiering the saturation effect. Several methos that measure or calculate the electrical parameters of a motor have alreay been propose in [10], [11]. These methos simply measure the phase inuctances but they nee an external circuit. Moreover, they nee to know the position information [10] or have to calculate a complex flux polynomial to obtain the synchronous inuctances [11]. The researchers in [12] measure the SynRM synchronous inuctances consiering the iron loss from a single phase test. The phase current, voltage, active power, position information, an c stator resistance are necessary for the synchronous inuctance ientification. In recent years, the Finite Element Metho (FEM) has been applie to simulate the parameters uner ieal conitions [13]. However, FEM requires the motor imensions an the material characteristics to calculate the electrical parameters. To consier the parameters in a real situation, the inuctances were calculate recursively from the measure voltages an currents, their previous values an the constant stator resistance [14]. The very important role of electrical parameters for sensorless control was consiere in [15]. By using the recursive least-square metho, the authors irectly ientifie the electrical parameters in the sensorless control of a SynRM. This metho estimate the electrical parameters by using the

2 492 Journal of Power Electronics, Vol. 10, No. 5, September 2010 Fig. 2. Inuctance as a function of rotor position. Fig. 1. Measurement iagram of stator inuctances using an LCR meter. measure voltages an currents, the ientifie matrices an their previous values. These conventional methos, in brief, are very complex to implement or can only be use uner constraine conitions. A synchronous PI current regulator is wiely use for ac machine rives ue to its capability in regulating ac signals over a wie frequency range [16], [17]. Electrical parameters are use to calculate the PI gains of a synchronous PI current regulator. As a result, the rive performance can be guarantee by using the exactly measure electrical parameters. This paper proposes a new metho that uses a synchronous PI current regulator to measure the exact electrical parameters of the SynRM at a stanstill, taking into full consieration the effects of both the switching evices an the connecting wire resistance. The influences of the parameters on the rive performance are also verifie through several experimental results. II. TWO CONVENTIONAL METHODS A. Using an LCR meter In general, the three phase inuctances of a SynRM are given by [18]: L(θ) = Ls L ms Lms Lms L s L ms L ms L ms L s cos(2nθ) cos(2nθ 2π 3 ) cos(2nθ + 2π 3 ) +L m cos(2nθ 2π 3 ) cos(2nθ + 2π 3 ) cos(2nθ) cos(2nθ + 2π 3 ) cos(2nθ) cos(2nθ 2π 3 ) (1) where, L s is the average stator self-inuctance, L ms is the stator mutual inuctance, L m is one of the stator inuctances ue to the rotor saliency, an N is the number of pole pairs. In a synchronous reference frame, the - an q- axis synchronous inuctances of the SynRM stator can be acquire by using the Park transformation. L = L s L ms + 1.5L m (2) L q = L s L ms 1.5L m. (3) Fig. 1 shows a measurement iagram of the two phase inuctances using an LCR meter. The inuctance expression between the two phases, L AB can be expresse as: L AB = 2L s 2L ms 3L m cos(2nθ 2π ). (4) 3 Applying (4) to (2) an (3), the - an q-axis inuctances of the SynRM can be erive in (5) an (6), respectively. L = L AB max 2 L q = L AB min. (6) 2 The LCR meter can measure the line to line resistances at the actual rotor terminals. The phase resistance R s can be easily obtaine by: R s = R AB,avg (7) 2 where, R AB,avg is the average resistance value between the A- an B-phases. L AB max an L AB min are the maximum an minimum inuctances between the A- an B- terminals accoring to the rotor position as shown in Fig. 2. B. Using the ac voltage an current source The principle of measurement using the ac voltage an current (calle the VI metho in this paper) is similar to that of the LCR meter shown in Figs. 1 an 2. The power system supplies a sine voltage to the A- an B- terminals. The inuctance between the two phases can be calculate as: L AB = 1 ω (V I (5) ) 2 4R 2 s (8) where, ω is the frequency of the applie sine voltage, I is the rms current that flows through the A-phase an the B-phase, V is the voltage between the two phases, an R s is the measure phase resistance from the prior c test. In the VI metho, the stator current an voltage can be measure by slowly rotating the rotor mechanically from 0 to 2π in one irection. The change in the line to line inuctances that occurs as the rotor is rotate is epicte in Fig. 2. The resultant synchronous inuctances L an L q can be calculate by using (5), (6), an (8). This metho has some isavantages in obtaining the profile of the inuctances. Firstly, it takes a lot of time to measure the inuctances. Seconly, it requires aitional equipment such as voltage/current meters, an an ac power supply. Thirly, using c resistance in an inuctance equation (8) causes measurement errors in calculating the synchronous inuctance ue to the error of the constant c resistance. Finally, in orer to get a wie range of values of the inuctances, measurements using a greater than nominal current (I rms > I nom ) coul heat an amage the SynRM because of the long term exposure to high temperature.

3 Parameter Ientification of a Synchronous Reluctance Motor by using 493 Fig. 3. Conceptual iagram for resistance measurement. III. PROPOSED ONLINE MEASUREMENT METHOD The conventional methos can only measure the electrical parameters of the motor. In orer to consier the effects of the switching evices as well as the connecting wires, the real inverter system must be analyze an use to measure the electrical parameters. A. Relationship between current eviation an electrical parameters The - an q-axis output voltages of a synchronous PI current regulator can be written at a stanstill (ω e =0) in the Laplace Transform Domain (LTD) as in (9) an (10). V (s)= 1 s Vq (s)= 1 s [I ] (s) I(s) r [K i cc + sk p cc ] (9) ] [I q (s) Iq r (s) [K iq cc + sk pq cc ] (10) where, K i cc = R ω cc, K iq cc = Rqω cc, K p cc = L ω cc, an K pq cc = L qω cc are the PI gains of the synchronous PI current regulator. R & R q, an L & L q are the known - an q-axis resistances an inuctances respectively, ω cc is the current regulator s banwith, which is irectly relate to the sampling time of the synchronous PI current regulator an the switching frequency [6]. V (s) an Vq the synchronous PI current regulator, while I (s) are the outputs of (s) an I q (s) are the - an q-axis reference currents calculate from the output of the spee controller. The terms, I r (s) an Ir q (s), are the real - an q-axis currents measure from the motor terminals. The mathematical moel of a SynRM is given by: v(t) r = R s i r (t) + L i r (t) ω e L q i r t q(t) i r q(t) vq(t) r = R s i r q(t) + L q + ω e L i r t (t) (11) where, v r(t) an vr q(t) are the - an q- axis terminal voltages in the synchronous reference frame. The LTD equation of (11) at stanstill can be erive as: { V r (s) = (R s + sl )I r(s) Vq r (s) = (R s + sl q )Iq r (s). (12) Fig. 3 shows a control block iagram of the SynRM rive system without a spee controller. The relationship between the reference voltages an the terminal voltages is as follows: { V r V q (s) = V r(s) + [R L + R sw ]I r(s) (s) = Vq r (s) + [R ql + R qsw ]Iq r (s) (13) where, R L an R ql are the - an q axis connecting wire resistances. R sw an R qsw represent the nonlinear effects of the switching evices. From (12) an (13), the current eviation between the real an the reference currents can be erive as: I (s) I r (s)= sl + R si K i cc + sk (s) r (14) p cc Iq (s) Iq r sl q + R q (s)= siq r (s) (15) K iq cc + sk p cc where, R = R s + R L + R sw an R q = R s + R ql + R qsw are the real - an q-axis resistances, respectively. B. Measurement of resistances at a stanstill In this section, a metho of etermining the resistance by using a synchronous PI current regulator is propose by using the above analysis. If K i cc is zero, the transfer function of the -axis current is easily erive as in (16) from (14). I r(s) I (s) = K p cc. (16) sl + R + K p cc When a step function of the -axis current reference is applie, the transient state equation of the -axis current can be erive as: i r (t) = i (t)k ( ) R p cc +K p cc L t 1 e. (17) R + K p cc Because L << R + K p cc, the -axis current at the steay state can be approximately obtaine as: K p cc i r (t) = i r (t). (18) R + K p cc From (18), the -axis resistance is calculate like (19). R = i (t) i r (t) K p cc K p cc. (19)

4 494 Journal of Power Electronics, Vol. 10, No. 5, September 2010 Fig. 4. Principle of inuctance measurement at a current. The real current is smaller than the reference current in (18), so the measure resistance is always larger than zero (19). The q-axis resistance is also given by: R q = ir q (t) i r q(t) K pq cc K pq cc. (20) When the information about the real current, the reference current an the arbitrary proportional gain is known from the rive system, the real - an q-axis resistances can be easily calculate by using (19), an (20) as shown in Fig. 3. C. Measurement of the stator inuctances The fact that the PI gains of the synchronous PI current regulator affect the current responses of the rive system was alreay proven in [6]. The gains can be calculate from the known resistances an inuctances as mentione above. If the PI gains are obtaine by using the exact electrical parameters, the real current tracks the reference current quite well. This means that the control performance of the current regulator epens on the electrical parameters. The system resistances that inclue the effects of the switching evices an the connecting wires are alreay known from the previous step, that is, R = R an R q = R q. (14) can be rearrange to get a current transfer function as in (21). I r(s) I (s) = ω cc(r + sl q) L s 2 + (ω cc L + R. (21) )s + R ω cc When the step function of the reference current is applie to (21), the -axis current can be erive as the equation of the transient state shown in (22). i r (t) = i (t) + k 1 e δt i (t) + k 2 e γt i (t) (22) where: k 1 = ω cc L 1 (γ δ) k 2 = ω cc L 1 (γ δ) ( L R ) δ ( ) R γ L δ = (ω ccl + R ) (ω cc L + R ) 2 4L ω cc R 2L γ = (ω ccl + R ) + (ω cc L + R ) 2 4L ω cc R 2L The current response of (22) is analyze as follows: At t = 0: i r (t) = i (t) + i (t) ω cc L 1 (γ δ) ( R γ R ) = 0 (23) δ At t = t 1, just before the steay state, e δt >> e γt (γ >> δ) is satisfie an the -axis current is approximately obtaine at t 1 as in (24): i r (t) r (t) + k 1 e δt i (t) (24) The current response in (24) can be ivie into three cases: Case (1): if L > L : k 1 > 0; i r (t) > i (t) : unerampe. Case (2): if L = L : k 1 = 0; i r (t) = i (t) : critically ampe. Case (3): if L < L : k 1 < 0; i r (t) < i (t) : unerampe. At t = + : e δt = 0, e γt = 0: i r (t) = i (t), the current reaches the steay state. The analysis of the q-axis current response is the same as the -axis current analysis that was just presente. It is known from the analysis of (24), that the real current can track the reference well if an only if the known inuctances are equal to the real inuctances. Therefore, only case (2) can be use to etermine the real inuctances.

5 Parameter Ientification of a Synchronous Reluctance Motor by using 495 Fig. 6. Experimental results of inuctance measurement using VI metho. Fig. 5. Experimental rive system for SynRM. The metho of measuring the inuctances is shown in Fig. 4, an is base on the following three steps: First, the proportional gain is ajuste to a small enough value to prouce an overshoot in the current response. Then, the proportional gain is increase step by step until the overshoot is eliminate. When there is no overshoot, the minimum proportional value is the accurate P gain. The real inuctance equals the proportional gain ivie by the banwith of the PI current regulator. The same proceure is neee to measure the q-axis inuctance. The resultant equations for the inuctance values are given in (25) an (26), respectively. L = L = K p cc /ω cc (25) L q = L q = K pq cc /ω cc. (26) IV. EXPERIMENTAL RESULTS Fig. 5 shows the control system of the SynRM that was use to verify the propose metho experimentally. This system consists of a DSP boar with a TMS320VC33 an FPGA, a ioe brige rectifier, an inverter using an IPM (Intelligent Power Moule), an a 3 HP SynRM with 4-poles. The sampling perio of the current regulator is 100 µs. The PWM switching frequency is 5 khz. A. Using the VI metho Two terminals of the SynRM were connecte to the ajustable ac power supply as shown in Fig. 1. The phase resistance was etermine by a prior c test. The stator currents an voltages were measure by slowly rotating the rotor mechanically from 0 to 2π in one irection, an the inuctances can be calculate by using (5), (6), an (8). Fig. 6 shows the experimental results of the measure inuctances by changing the current range from 1 to 10 A. In the real system, it is not easy to measure the exact electrical parameters of the SynRM by using the VI metho ue to the saturation effect of the stator inuctance as shown in Fig. 6. This effect as an aitional error to the stator inuctance of the VI metho. Fig. 7. B. Propose metho Experimental results of q-axis resistances. 1) Measurement of resistances: Fig. 7 shows the current responses of the - an q- axis currents at 4 A an the calculate - an q-axis resistances in the steay state by using (19) an (20), respectively. The P gain is chosen arbitrarily only to observe the waveform of the current response an to measure the - an q-axis resistances incluing the effects of the inverter an the connecting wires. The experimental results of the - an q-axis resistances an the c resistance R c of the VI metho are shown in Fig. 8. The current level is easily varie by using the reference current of inverter system from 0 to 10 A with the short uration of the one pulse current as shown in Fig. 7. The resistance steaily ecreases when the test current increases. This phenomenon mainly comes from the nonlinear characteristics of the switching evices. A small eviation between the - an q- axis resistances results from the Park transformation. In orer to etermine the exact integral gains (I-gains) of the synchronous PI current regulator, the - an q-axis resistances must be use. Inaccurate integral gains can cause a eterioration of the system performance not only in the steay state but also in the transient state. The propose metho, that exactly measures the electrical parameters of the inverter fe SynRM incluing the effect of the switching evices an the connecting wires, guarantees improve rive performance of SynRMs. 2) Measurement of the stator inuctances: Fig. 9 shows the waveforms of the q-axis currents for three cases: unerampe, critically ampe, an overampe. First, the proportional gain (K p cc ) of the -axis or the q- axis is set to a small value by using a small input inuctance to prouce an overshoot as shown in Figs. 9 (a) an (), respectively. Then, K p cc is increase slowly to eliminate the overshoot. Figs. 9 (b) an (e) show the critically ampe current

6 496 Journal of Power Electronics, Vol. 10, No. 5, September 2010 Fig. 8. Experimental results of q-axis an c resistances by using the propose an c metho. responses with suitable gains an accurate parameters. The synchronous inuctances are calculate irectly by using the accurate proportional gains an the banwith as shown in (25) an (26), respectively. Fig. 10 shows a comparison of the experimental results of inuctances between the VI metho an the propose metho. The q-axis inuctance approaches the saturate region earlier than the -axis inuctance because of the rotor structure in the SynRM. As shown in Fig. 10, the propose metho is implemente by using the short uration of the step current to measure the electrical parameters. In aition, the measurement errors between the VI metho an the propose algorithm below 3[A] are generate by measurement noises in the regions of the low reference currents. A better system response was obtaine from the well tune parameters an PI gains not only in the steay state but also in the transient state as shown in Fig. 11. The inuctance eviation between the two methos is small as shown in Fig. 10. If the parameters of the VI metho are use, the large eviation of stator resistance seen in Fig. 8 causes an overampe response as shown in Fig. 11. Therefore, the propose metho was use to exactly measure the electrical parameters of SynRMs as shown in Figs. 7, 8, 9, 10, an 11. C. Effect of motor parameters on system response To evaluate the feasibility of the propose metho, the inverter fe SynRM is teste from stanstill to 500 r/min without a loa. The PI gains calculate from the parameters of the VI an propose methos were turne to aapt to the operating currents. The experimental waveforms of the -an q-axis currents are shown in Fig. 11 (a), (b), (c), an (), (e), (f), respectively. V. CONCLUSIONS This paper proposes a new algorithm to measure the electrical parameters of a SynRM by using a synchronous PI current regulator at a stanstill. The propose algorithm can be easily an safely implemente by simultaneously using the short one-pulse an close equations of resistance an synchronous inuctances. Furthermore, the measurement time can be greatly reuce. In aition, the rive system itself is capable of measuring the electrical parameters, taking into full consieration the effects of the switching evices, connecting wires, an saturation by using the propose metho. It oes not nee any external or aitional equipment for the Fig. 9. Experimental results of q-axis inuctances measurement by using the propose algorithm. (a) -axis current unerampe. (b) -axis current critically ampe. (c) -axis current overampe. () q-axis current unerampe. (e) q-axis current critically ampe. (f) q-axis current overampe. Fig. 10. Comparison results of synchronous q-axis inuctances between VI metho an propose metho. measurement. Moreover, this metho can measure the exact electrical parameters without any information on the motor s imension or material characteristics as in the case of FEM. The effectiveness of the propose algorithm is verifie through several experimental results. ACKNOWLEDGMENT This work was supporte by the Energy Efficiency & Resources of the Korea Institute of Energy Technology Evaluation an Planning (KETEP) grant fune by the Korea Government Ministry of Knowlege Economy (No P- EO-HM-E ).

7 Parameter Ientification of a Synchronous Reluctance Motor by using 497 [12] Senjyu, T., Omoa, A., an Uezato, K., Parameter measurement for synchronous reluctance motors consiering stator an rotor iron loss, Electric Machines an Drives, International Conference IEMD 99, May [13] A. A. Arkaan, F. N. Isaac, an O. A. Mohamme, Parameters evaluation of ALA synchronous reluctance motor rives, IEEE Trans. Magn., Vol. 36, No. 4, Jul [14] Kilthau. A an Pacas, J, Parameter measurement an control of the synchronous reluctance machine incluing cross saturation, IEEE IAS Annual meeting, [15] Shinji Ichikawa, Mutuwo Tomita, Shinji Doki, an Shigeru Okuma, Sensorless control of synchrnous reluctance motors base on extene EMF moels consiering megnetic saturation with online parameter ientification, IEEE Trans. In. Applicat., Vol. 42. No. 5 Sep./Oct [16] Kazuhiro Ohyama an Katsuji Shinohara, Small-signal stability analysis of vector control system of inuction motor without spee sensor using synchronous current regulator, IEEE Trans. In. Applicat., Vol. 36, No. 6, Nov./Dec [17] Hyunbae Kim an Lorenz, R.D, Improve current regulators for IPM machine rives using on-line parameter estimation, IEEE IAS Annual Meeting, Vol. 1, [18] Paul C. Kreause, Oleg Wasynczuk, an Scott D. Suhoff, Analysis of Electric Machinery, IEEE Press, pp , Seon-Hwan Hwang was born in Chungnam, Korea, in He receive his B.S. an M.S. in Electrical Engineering from Pusan National University, Busan, Korea, in 2004 an 2006, respectively. He is currently working towar his Ph.D. at Pusan National University. His research interests inclue power conversion an electric machine rives. Fig. 11. Experimental results of spee an q-axes current responses. (a), (b), an (c) VI metho. (), (e), an (f) propose algorithm. R EFERENCES [1] Jovanovic, M.G., Betz, R.E., an Jian Yu, The use of oubly fe reluctance machines for large pumps an win turbines, IEEE Trans. In. Applicat., Vol. 38, No. 6, Nov./Dec [2] Vagati, A., Pastorelli, M., an Franceschini, G, High-performance control of synchronous reluctance motors, IEEE Trans. In. Applicat., Vol. 33, No. 4, Jul./Aug [3] Seog-Joo Kang, Jang-Mok Kim, an Seung- Ki Sul, Position sensorless control of synchronous reluctance motor using high frequency current injection, IEEE Trans. Energy Conversion, Vol. 14. No. 4, Dec [4] Chalmers, B.J. an Musaba, L., Design an fiel-weakening performance of a synchronous reluctance motor with axially laminate rotor, IEEE Trans. In. Applicat., Vol. 34, No. 5, Sep./Oct., [5] R.E.betz, R.Lagerquist, an M. Jovanovic, T. J. E Miller, R. Mileton, Control of synchronous reluctance motor, IEEE Trans. In. Applicat., Vol. 29, No. 6, Nov./Dec [6] Fernano Briz, Michael W. Degner, an Robert D. Lorenz Analysis an esign of current regulators using complex vectors, IEEE Trans. In. Applicat., Vol. 36, May/Jun [7] Lubin, T., Razik, H., an Rezzoug, A., Magnetic saturation effects on the control of a synchronous reluctance machine, IEEE Trans. Energy Conversion, Vol. 17, No. 3, Sep [8] Wung, P.Y.P. an Puttgen, H.B, Synchronous reluctance motor operating point epenent parameter etermination, IEEE Trans. In. Applicat., Vol. 28, No. 2, Mar./Apr [9] Ping Zheng, Thelin, P., Anyuan Chen, an Norlun, E., Influence of saturation an saliency on the inuctance of a four-quarant transucer prototype machine, IEEE Trans. Magn., Vol. 42, No. 4, Apr [10] Wen-Nan Huang, Ching-Cheng Teng, Chih-Hsing Fang, an ChihHsin Chen, Inuctance measurement an estimation metho utilizing LC circuit analysis techniques uner ynamic operation for switche reluctance (SR) machines, Inustrial Electronics Society, 30th Annual Conference of IEEE, Vol. 3, [11] Nikolay Raimov, Natan Ben-Hail, an Raul Rabinovici, Inuctance measurements in Switche reluctance machines, IEEE Trans. Magn., Vol. 41. No. 4, Apr Jang-Mok Kim was born in Busan, Korea, in August He receive his B.S. from Pusan National University in 1988, an his M.S. an Ph.D. from Seoul National University, Korea, in 1991 an 1996, respectively, in the Department of Electrical Engineering. From 1997 to 2000, he was a Senior Research Engineer with the Korea Electrical Power Research Institute (KEPRI). Since 2001, he has been with the School of Electrical Engineering, Pusan National University (PNU), where he is currently a faculty member. In aition, he is a Research Member of the Research Institute of Computer Information an Communication at PNU. His present interests inclue the control of electric machines, electric vehicle propulsion, an power quality. Huynh Van Khang was born in Binh Dinh, Vietnam, in He receive his B.S. from the Ho Chi Minh City University of Technology, Vietnam in 2002, an his M.S. from Pusan National University, Korea in Currently, he is a researcher in the Electromechanics group, Aalto University, Finlan where he is working towar his Ph.D. His research interests inclue electrical machines an rives. Jin-Woo Ahn was born in Busan, Korea, in He receive his B.S., M.S., an Ph.D. in Electrical Engineering from Pusan National University, Busan, Korea, in 1984, 1986, an 1992, respectively. He has been with Kyungsung University, Busan, Korea, as a Professor in the Department of Electrical an Mechatronics Engineering since He was a Visiting Professor in the Department of Electrical Engineering, UW-Maison, USA. He is the author of five books incluing SRM an the author of more than 100 papers. His current research interests are motor rive systems an electric vehicle rives. Dr. Ahn was liste in Who s Who in the Worl 2003 (The Marquis Who s Who Publications Boar, USA) an also in Leaing Scientists of the Worl 2006 (International Biographical Centre, UK). He is a Senior Member of IEEE, a Senior Member of Korean Institute of Electrical Engineers an a Member of the Korean Institute of Power Electronics.