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566 IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 50, NO. 1, JANUARY/FEBRUARY 2014

Efficiency Comparison Between Si-IGBT-BasedDrive and GaN-Based Drive

Kohei Shirabe, Member, IEEE, Mahesh M. Swamy, Member, IEEE, Jun-Koo Kang, Member, IEEE,Masaki Hisatsune, Member, IEEE, Yifeng Wu, Member, IEEE, Don Kebort, and Jim Honea

Abstract—High motor efficiency, lower torque ripple, close toideal sinusoidal motor current waveform, smaller filter size, etc.are a few of the advantages of using high-frequency pulsewidthmodulaton (PWM) (in the range of 50 to 100 kHz) in motor driveapplications. However, higher frequency PWM is also associatedwith voltage reflection and motor insulation breakdown issues.Due to high losses, Si IGBT-based inverters cannot be operated athigh switching frequency. Work on SiC and GaN-based inverterhas progressed and variable-frequency drives (VFDs) can now beoperated efficiently at carrier frequencies in the 50 to 200 kHzrange, using these devices [1] because of extremely low turn-onand turn-off losses. At high frequency, physical and electricalrating of output filter reduces, thereby improving efficiency. Lossin ac motors also reduces because of sinusoidal waveform. All theabove features put together improves system efficiency. This paperfocuses on comparing the efficiency of Si-IGBT-based drive witha 6-in-1 GaN module-based drive, which is operating at a carrierfrequency of 100 kHz with an output sine wave filter. Experimentalresults show the GaN-based drive has a better system efficiencycompared to the standard Si IGBT-based drive.

Index Terms—GaN-based variable-frequency drive, high-efficiency motor-drive system, high-frequency drives, outputsine-wave filter.

I. INTRODUCTION

T RADITIONALLY, insulated gate bipolar transistor(IGBT)-based voltage-source inverter (VSI) outputs are

pulse width modulated at a carrier frequency ranging from2.0 kHz to 15 kHz. In large power applications, the carrierfrequency is lower than that in smaller power applications dueto thermal issues pertaining to the power semiconductor inrelation with its current rating.

When high-frequency pulsewidth modulation (PWM) is im-pressed across the terminals of an ac motor controlled by a VSI-based drive, there are always voltage transient and insulationbreakdown issues. Efficiency of converting electrical input

Manuscript received October 19, 2012; revised January 14, 2013; ac-cepted March 8, 2013. Date of publication November 13, 2013; date ofcurrent version January 16, 2014. Paper 2012-IPCC-556.R1, presented at the2012 IEEE Energy Conversion Congress and Exposition, Raleigh, NC, USA,September 15–20, and approved for publication in the IEEE TRANSACTIONS

ON INDUSTRY APPLICATIONS by the Industrial Power Converter Committeeof the IEEE Industry Applications Society.

K. Shirabe, M. M. Swamy, J.-K. Kang, and M. Hisatsune are with YaskawaAmerica, Inc., Waukegan, IL 60085 USA (e-mail: [email protected]; [email protected]; [email protected]; [email protected]).

Y. Wu, D. Kebort, and J. Honea are with Transphorm Inc., Goleta, CA93317 USA (e-mail: [email protected]; [email protected];[email protected]).

Color versions of one or more of the figures in this paper are available onlineat http://ieeexplore.ieee.org.

Digital Object Identifier 10.1109/TIA.2013.2290812

power to mechanical output power also suffers due to lossesassociated with PWM waveforms. There are many publishedstudies that document these influences [3]–[7].

To reduce the loss in ac motors due to PWM waveform, tra-ditionally output sine wave filters are employed. Unfortunately,using a sine wave filter in many cases shifts some of the lossassociated with PWM from the motor to the sine wave filter.In addition, the size and cost of the sine wave filter cannot beignored, especially in large power applications, where the PWMcarrier frequency cannot be increased to high values due to thepower loss constraints imposed by Si IGBTs at those powerlevels.

Using the latest high-frequency SiC or GaN power switches,it is now possible to operate efficiently a VFD with highPWM carrier frequency [1], [2]. Higher PWM carrier frequencyallows the design of sine wave filters with a higher cornerfrequency, which in turn reduces the value of the filter inductorand filter capacitor. The size and cost of the output sine wavefilter also reduce. By supplying near to sinusoidal voltage andcurrent waveform into an ac motor reduces the losses associatedwith PWM waveforms.

Soft magnetic materials with different chemical compositionthat is tailored for high frequency PWM applications can bedeveloped to reduce loss in the filter inductor and improve theoverall efficiency of filtering.

In many ac motor drive applications, it is becoming necessaryto control position, speed, and torque to an ever increasingdegree of precision. Control without the use of position andspeed feedback is almost a requirement in many demandingapplications. Updating the voltage and current feedback signalsmore frequently and issuing new command signals accordinglyare desired features to have in a robust controller. All of this canbe brought to bear if there is a power semiconductor device thatcan react to the new command signals at an appropriately fastrate. SiC and GaN-based semiconductor devices are beginningto show such characteristics. It is now possible to controlkilowatts of power with the aforementioned semiconductordevices switching in the 50 to 200 kHz range. However, it isimportant to point out that considering the total time neededto complete complicated mathematical functions for sensor-lessvector control, a practical operating carrier frequency is about30 kHz to 50 kHz. High power VFDs are presently operatedat a PWM carrier frequency of around 2 kHz to 4 kHz dueto restrictions imposed by Si IGBTs. In the future, due to theavailability of switches like GaN and SiC, these operations canbe carried out at a PWM carrier frequency of 30 kHz to 50 kHzthereby enabling use of smaller sized filter components that can

0093-9994 © 2013 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission.See http://www.ieee.org/publications_standards/publications/rights/index.html for more information.

SHIRABE et al.: EFFICIENCY COMPARISON BETWEEN Si-IGBT-BASED DRIVE AND GaN-BASED DRIVE 567

Fig. 1. (a) Schematic of a hybrid HEMT GaN module comprising of a lowvoltage normally off Si MOSFET in series with a normally on high voltageGaN HEMT device. (b) Symbol for it.

provide clean power to the motors and consequently improvetheir reliability.

Though work on exploiting the benefits of high carrier fre-quency to achieve high speed robust control is progressing,the present paper focuses on improvement in system efficiencyobtained on using a VFD modulated at 100 kHz with an outputsine wave filter. Experimental results are given to demonstratethe gain in motor efficiency and system efficiency on using aGaN-based 100 kHz VFD, operating in V/F mode.

Section II discusses the characteristics of the GaN moduleemployed in the test. It also points out the salient differ-ences between Si IGBTs and GaN module used. The designcharacteristics of the output sine wave filter are discussed inSections III–V present experimental test results. Section VIconcludes the paper.

II. GaN DEVICE CHARACTERISTICS

In this section, characteristics of the GaN module employedare discussed. The unit cell device used in this paper is a GaNhybrid HEMT (High Electron Mobility Transistor) module. Itis a 600 V, 30 A three-phase GaN power module bearing apart number TPT3044M, which is an engineering prototypedeveloped by Transphorm. The GaN module incorporates anormally off low-voltage Si device at the input and a normallyon high-voltage GaN HEMT at the output in a cascode form.The combined device is normally off having a gate thresholdof +2.1 V (typical) at 1 mA drain current and a drain leakageof 10 μA (typical) at a gate-source voltage (VGS) of 0 Vand drain-source voltage (VDS) of 600 V. The structure of thehybrid HEMT module employed is shown in Fig. 1 and is muchdifferent from the type discussed in [1], which is a normally offdevice with no cascode switch.

A. Turn-On Characteristics

The circuit used for studying the switching characteristics ofthe GaN module is shown in Fig. 2.

From Fig. 1, it is clear that the turn-on and turn-off char-acteristics of the hybrid HEMT module are influenced by thecharacteristics of the series Si-based MOSFET switch that isused as a cascode switch. This MOSFET is rated for 30 V,11 A at a case temperature of 70 deg. C. The total switch chargeto turn on the MOSFET is 4.2 nC. The turn-on delay time is8.2 ns and the rise time is only 11 ns, yielding an excellentturn-on characteristics. Turn-on waveform is shown in Fig. 3.

Fig. 2. Circuit for evaluating the switching characteristics of GaN module.Gate driver was made by Transphorm, Inc.

Fig. 3. Turn-on waveform with inductor current IOUT at 10 A.

In Fig. 3, the turn-on delay is measured to be 4 ns and theturn-on rise time is measured to be 3.5 ns. This is much fasterthan that achieved using a standard Si-based IGBT with similarvoltage and current rating. For example, the equivalent Si IGBTsuitable for comparison is CP30TD1-12 made by Mitsubishi.The best achievable turn-on delay time is 80 ns and the turn-onrise time for this IGBT is about 50 ns. Again, the reason canbe attributed to the gate-emitter characteristics of the Si IGBTwhich has a total gate charge of 98 nC compared to 4.8 nC forthe cascode switch. Fig. 3 also shows that the turn-on Δv/Δtfor the GaN HEMT device is about 103 kV/μsec.

B. Turn-Off Characteristics

As mentioned earlier, to switch off the GaN HEMT module,we need to turn off the low voltage Si MOSFET. Since theMOSFET used is low voltage type, the stored charge in thegate-source junction is very low and it is easy to remove itquickly to ensure fast turn off. In addition, since the devicebeing turned off is a MOSFET, it does not require a negativegate drive. In fact, applying a negative voltage across gate tosource can be counterproductive, since more energy is neededto flood the space directly under the gate structure with negativevoltage which will create positively charged holes under thegate structure. Movement of holes to the surface of the gate


Fig. 4. Turn-off waveform with inductor current IOUT at 10 A.

requires movement through a resistive channel which is respon-sible for power loss. Also, during turn-on process, this chargeneeds to be replaced with electrons to establish a conductingchannel. The extra charge concentration will require extrapower and more time to remove this charge, which increasesturn-off delay time and increases turn-off gate drive power.Hence, an optimal solution will be to simply apply zero volts sothat the gate-source junction is shorted with the gate resistancein the circuit. Sometimes, if the trace between the gate driverboard and the GaN HEMT device is unavoidably long, thenone may consider applying a low negative voltage to quicklydischarge the parasitic capacitance of the trace. In the testingdone here, no negative gate voltage was applied. The turn-offcharacteristics are shown in Fig. 4.

From Fig. 4, it is observed that the turn-off time is about15 ns. This is much faster than that achievable using a standardSi-based IGBT with similar voltage and current rating. The bestachievable turn-off time for CP30TD1-12 per the manufactureris about 300 ns, with enough negative gate drive. The reasoncan be attributed to the fact that unlike MOSFETs, the IGBThas an additional junction, which contributes to tail currentduring turn-off process. This is instrumental in the slower turn-off characteristics observed in IGBTs compared to MOSFETs.The additional junction also causes parasitic latch up problemsas described in [8]. In order to overcome this latch-up problem,it is advisable to provide negative gate voltage in case of IGBTs[8]. In Fig. 4, the turn-off delay is measured to be 10 ns andthe turn-off fall rise time is measured to be 7 ns. The turn-offΔv/Δt is seen to be about 53 kV/μs.

C. No Free Wheeling Diode in GaN HEMT

It is important to point out that the basic high voltage GaN-based HEMT device is a bidirectional module with high voltageblocking characteristics when VDS > 0. The actual conductingpart of the HEMT device is a channel of pure electron flowin a crystalline structure with no junctions. Hence, current canflow in either direction. Hence, when the source voltage ismore positive with respect to the drain terminal, then currentcan flow in the reverse direction quite efficiently. The currentin the cascode MOSFET flows through the body diode of the

Fig. 5. Empirically obtained switching loss versus inductor current.

Fig. 6. (a) Schematic of an output LC filter for PWM filtering; (b) Transferfunction of the LC output filter with a load. Red. fc = 3 kHz and fr = 827 Hz;Brown. fc = 100 kHz and fr = 25 kHz.

MOSFET, which has quite good intrinsic turn-on and turn-off characteristics. Since the cascode switch is a low-voltageswitch, it has a short drift region with little charge holdingcapacity. This significantly reduces the reverse recovery charge,Qrr and makes it fast to turn off with little power loss. The bodydiode of the MOSFET used in the GaN HEMT module here hasa forward drop of only 1 V and has a typical reverse recoverytime of 14 ns. The reverse recover charge stored when thebody diode gets reverse biased (Qrr) is typically about 40 nCat 400 V, making it to turn on and turn off very fast withlittle power loss. Typical values of reverse recovery currentfor comparably rated Si IGBT are 200 ns with a Qrr value ofapproximately 900 nC. This is one of the reasons why a SiIGBT cannot be switched at 100 s of kHz.

Since, there is physically no body diode across the GaNHEMT device, it has low losses during turn off and is wellsuited for inverter application in an H-bridge configuration. Itshould be pointed out here that the GaN device characteristicdoes not show the device current. This is because any current


Fig. 7. Schematic of the test setup for the GaN-based drive.

measuring method would add inductance disrupting the opera-tion integrity during such high speed operation.

Traditionally current and voltage waveforms of the switchingsemiconductor are measured and switching losses are calcu-lated through mathematical integration. However, with GaN,the switching speed is 10–50 times faster. Hence, as mentionedearlier, insertion of a current probe causes unwanted induc-tance, disrupting the operation integrity and leading to unsafespikes. Due to this reason, the only effective way to character-ized loss is extracted by efficiency tests of dc-dc converter atvarious current and frequencies. Switching loss characteristicof the module used here is experimentally obtained using thecircuit of Fig. 2 and is reported here in Fig. 5.

III. OUTPUT SINE WAVE FILTER CHARACTERISTICS

As mentioned in the Introduction section, traditionally PWMwaveforms are applied across ac motor terminals to operatethem at variable speed to achieve desired performance. How-ever, ac motors respond to only the fundamental componentsand the harmonics associated with PWM wave form manifestthemselves as loss in electric motors. This reduces the overallsystem efficiency. One way around this is to filter the PWMwaveform using output sine wave filters but as mentioned ear-lier, a significant part of the loss in the motor is simply moved tothe filter thereby not affecting the overall system efficiency to agreat extent. When the processed power is large, the switchingfrequency is low which makes the filter bulky and expensive.

Given the fact that high speed switches that can process largeamounts of power are in near sight, it is conceivable that the sinewave filters can be designed to have a higher corner frequency,thereby reducing their size and improving the filter efficiencysince filtering very high frequency components can be achievedusing soft magnetic material that are characterized by low corelosses. In other words, making use of power switches that canbe efficiently switched at higher switching frequency, one coulddesign small sized, more efficient output sine wave filters. Thecombination of efficient power switches, small sized low losssine wave filter can yield drive systems that are more efficientthan the drive systems that are presently in use.

Fig. 8. Photograph of GaN module and inverter with the GaN module. Sampleshown was used for the test. Electrical specifications: VLL(output) = 230 V,Output current Io = 14 A, 6-in-1 module.

In this section, an attempt is made to design a high frequencysine wave filter using soft magnetic material that has low lossand good performance. Such a filter is used in conjunction withthe GaN HEMT device in a 6-in-1 module VFD configuration,operating in V/F mode at a switching frequency of 100 kHz.

The output sine wave filter shown in Fig. 6(a) is used to filterthe output PWM waveform so that the line-line voltage at themotor terminals is sinusoidal. This also helps in alleviating theproblems associated with high Δv/Δt of the output voltage thatcauses high surge voltages at the motor terminals.

The resonance frequency (fr) of the sine wave filter ischosen to be in between the output fundamental frequencyfout and the carrier frequency fc. However, while selectingthe resonant frequency, influence of the leakage inductance ofthe motor should also be considered. The resonance frequencyequation uses the value of filter inductance LF , and the filtercapacitance CF as given by

fr =1

2π√LFCF

. (1)

To limit the carrier-frequency current into the filter capacitor,LF should be large. However, excessively large values for LF

should be avoided to limit the fundamental frequency voltagedrop across it under loaded conditions.

The resonance frequency fr should be in between the fun-damental output frequency fout, and carrier frequency fc, i.e.,


Fig. 9. Schematic of the test setup for the Si-based drive operating with a carrier frequency of 15 kHz.

fout � fr � fc. Since it is now possible to use a high carrierfrequency, the value of fr can be chosen to be much higher thantraditionally done with IGBT drives. From (1), it is clear thathigher resonant frequency selection yields a much lower valuefor the inductance and capacitance of the output sine wave filter.

The transfer function for a typical LC filter for filtering thePWM waveform is shown in Fig. 6(b). The attenuation abovethe cutoff frequency is high and the filter attenuates most ofthe high frequency component. Since the resonant frequencyis much lower than the carrier frequency, damping resistorsare not practically required—core loss component in the filterinductor can be used to achieve some damping. The torqueproducing fundamental components (low frequency) are notfiltered and are allowed to pass. The filter capacitor is requiredto have high current handling capacity because of the high fre-quency current components that flow into it. However, at highercarrier frequencies, the value of the filter capacitor needed issmall and so the capacitor current is well contained. Studieshave shown that keeping the inverter switching frequency to beat least five to seven times the resonant frequency of the low-pass filter yields optimum results.

In Fig. 5(b), the traditional filter (shown in red color) isdesigned with a resonant frequency of 480 Hz for a carrierfrequency of 3 kHz. Including the load impedance, the resonantfrequency is 827 Hz (LF = 2.1 mH, CF = 18 μF). Increasingthe carrier frequency to 100 kHz (shown in brown color) allowsthe resonant frequency to be as high as 25 kHz. The resonatinginductor needed is only 69 μH. The resonating capacitor neededis only 0.6 μF. This allows for significant reduction in size andcost of the filter.

Fig. 6(b) also shows that having the capability of switchingthe inverter switches at 100 kHz allows operation at higherfundamental frequency which is useful in many high speedapplications, like centrifuges, compressors, etc.

IV. EXPERIMENTAL SETUP AND TEST RESULTS

Tests were conducted to compare the inverter and systemefficiency between a Si-based drive and a GaN-based drive.This section discusses the results obtained from these tests. The

test setup is shown in Fig. 7. The filter inductor in the case ofGaN-based drive is 0.22 mH and the filter capacitor is 0.1 μF,resulting in an approximate corner frequency of 34 kHz. Boththe Si-based drive and the GaN-based drives were poweredfrom an external dc power source. Pin is the electrical inputpower, Po is the ac output power, and Pm is the mechanicalshaft power. Photograph of a GaN inverter is shown in Fig. 8.Schematic of the test setup employing a standard IGBT-baseddrive is shown in Fig. 9.

For efficiency calculations, the dc input is considered asthe electrical input power. Figs. 7 and 9 also show the pointswhere measurements were made. It is important to note that theGaN-based inverter was operated with a sine wave filter andthe loss of sine wave filter is included in the drive efficiencycalculations, while the Si-based inverter was operated withoutany output sine wave filter.

A. Test Results

Efficiency test results are given in Table I for GaN-baseddrive and in Table II for the standard Si-based drive made byYaskawa. Overall, system efficiency is measured taking thetransducer power as output and dc power as input. The systemis loaded in steps of 0.2 kW up to the rated power of 2.0 kW.Command frequency for both drives is kept at 60 Hz. Efficiencyplots are shown in Fig. 10.

It should be noted that the Si IGBT-based inverter wastested with no sine wave filter. This was deliberately done toinvestigate the extra losses that are incurred in the ac motor dueto PWM waveform. The distance between the drive and the acmotor in both cases was maintained at 3 m.

V. CONCLUSION

In this paper, the operating characteristics of a normallyon GaN HEMT device with a normally off low voltage Si-based MOSFET in cascode have been discussed. It has beenshown that the cascode combination is well suited for bridgeconfigurations since the resulting device has the advantage oflow switching losses, low conduction losses, and operation that


TABLE IMEASURED EFFICIENCY FOR GaN-BASED DRIVE

TABLE IIMEASURED EFFICIENCY FOR Si-IGBT DRIVE

Fig. 10. (a) Efficiency of inverter with respect to output electrical power (without motor efficiency). (b) System efficiency (mechanical output power to electricalinput power) as a function of mechanical output power.

does not require any external freewheeling diode. Advantagesof high PWM carrier frequency have also been highlighted. Testresults show that the inverter efficiency as well as the systemefficiency is higher using a GaN-based PWM drive operatingat a carrier frequency of 100 kHz. It is important to point outthat most variable frequency applications do not operate at ratedload all the time. Statistically speaking, most pump and fanapplications that use V/F mode of operation, operate at around50% to 70% load condition. From the results presented here, the

light load system efficiency observed for the GaN-based VFDsystem is much better than that for the Si IGBT-based VFDsystem.

Further, GaN-based drive with an output sine wave filter hasbetter efficiency compared to the Si-based drive without a sinewave filter. In other words, the switching and conduction loss inthe 6-in-1 GaN HEMT device operating at 100 kHz is seen to bemuch lower than Si-based IGBT inverter operating at 15 kHz.The size of the output sine wave filter is very small as can be


seen in Fig. 7. The loss in the sine wave filter is much lower thanthe extra losses seen in the ac motor when no filter was used.The system tested here is rated for 2.0 kW. However, the basicidea that GaN-based drive yields a better system efficiencycompared to Si-IGBT-based drive holds true for larger powerratings as well. The absence of audible PWM noise in the motorand in the output sine wave filter was noticeable.

REFERENCES

[1] M. Ishida, Y. Uemoto, T. Ueda, T. Tanaka, and D. Ueda, “GaN Switchingpower devices,” in Proc. Int. Power Electron. Conf., 2010, pp. 1014–1017.

[2] T. Morita, S. Tamura, Y. Anda, M. Ishida, Y. Uemoto, T. Ueda, T. Tanaka,and D. Ueda, “99.3% efficiency of three-phase inverter for motor driveusing GaN-based gate injection transistors,” in Proc. Int. Power Electron.Conf., 2011, pp. 481–484.

[3] M. J. Melfi, “Quantifying the energy efficiency of motors on inverters,”IEEE Ind. Appl. Mag., pp. 37–43, Nov./Dec. 2011.

[4] Induction Motors Fed by PWM Frequency Inverters, WEG Motors,Technical Guide, Publication 028, Dec. 2009. [Online]. Available: www.weg.net

[5] A. Boglietti, A. Cavagnino, and A. M. Knight, “Isolating the impact ofPWM modulation on motor iron losses,” in Conf. Rec. IEEE IAS Annu.Meeting, 2008, pp. 1–7.

[6] D. M. Ionel, M. Popescu, M. I. McGilp, T. J. E. Miller, S. J. Dellinger, andR. J. Heideman, “Computation of core losses in electrical machines usingimproved models for laminated steel,” IEEE Trans. Ind. Appl., vol. 43,no. 6, pp. 1554–1564, Nov./Dec. 2007.

[7] A. Boglietti, A. Cavagnino, and M. Lazzari, “Fast method for the ironloss prediction in inverter-fed induction motors,” IEEE Trans. Ind. Appl.,vol. 46, no. 2, pp. 806–811, Mar./Apr. 2010.

[8] C. J. Melhourne and L. Tang, “Transient effects of PWM drives on induc-tion motors,” in Conf. Rec. IEEE IAS Annu. Meeting, 1995, pp. 59–65.

[9] M. M. Swamy, T. Kume, and N. Takada, “An efficient resonant gate-drivescheme for high-frequency applications,” IEEE Trans. Ind. Appl., vol. 48,no. 4, pp. 1418–1431, Jul./Aug. 2012.

[10] G. Deboy, N. Marz, J. P. Stengl, H. Strack, J. Tihanyi, and H. Weber, “Anew generation of high voltage MOSFETs breaks the limit line of silicon,”in Proc. IEDM., 1998, pp. 683–685.

[11] D. Christen, U. Badstuebner, J. Biela, and J. W. Kolar, “Calorimetricpower loss measurement for highly efficient converters,” in Proc. Int.Power Electron. Conf., 2010, pp. 1438–1445.

Kohei Shirabe (M’11) received the B.S. and M.S.degrees in electrical engineering from NagasakiUniversity, Nagasaki, Japan, in 2004 and 2006,respectively.

In 2006, he joined Yaskawa Electric Corp.,Kitakyushu, Japan. From 2006 to 2011, he was a Se-nior Engineer and developed industrial inverter prod-ucts. He joined Yaskawa America, Inc., Waukegan,IL, USA, in 2011 as an R&D Engineer, where he iscurrently working in the area of motor drives. Hisinterests include wide-band-gap devices, high-speed

switching circuits, and power topology research.

Mahesh M. Swamy (S’86–M’92) received theB.Eng. degree from MMM Engineering College,Gorakhpur, India, in 1983, the M.S(Eng.) degreefrom the Indian Institute of Science, Bangalore,India, in 1986, and the Ph.D. degree from the Uni-versity of Victoria, Victoria, BC, Canada, in 1991.

In 1992, he joined Energy Management Corpora-tion, Salt Lake City, UT, USA, as a Senior ResearchEngineer where he worked on industrial ac motordrives. In 1996, he joined MTE Corporation as theDirector of Engineering. Since 1997, he has been

with the R&D group at Yaskawa America, Inc., Waukegan, IL, USA. Hisinterests are in inverter drives and power electronics.

Dr. Swamy is an active member of the IEEE Industry Applications, IEEEPower Electronics, and IEEE Industrial Electronics Societies.

Jun-Koo Kang (M’93) received the B.S., M.S., andPh.D. degrees in electrical engineering from SeoulNational University, Seoul, Korea.

From 1988 to 1997, he was with the R&D Centerof LG Industrial Systems where he was mainly in-volved in the development of general-purpose drivesand gearless elevator drives. In 1999, he joined theCorporate R&D Center of Yaskawa Electric Corpo-ration, Kitakyushu, Japan, where he was a Managerin the Mechatronics R&D Department. He workedon the development of matrix converters and other

industrial drives. He is currently with Yaskawa America Inc., Waukegan,IL, USA.

Masaki Hisatsune (M’11) received the B.S. andM.S. degrees in electrical engineering from KyushuInstitute of Technology, Fukuoka, Japan, in 1992 and1994, respectively.

In 1994, he joined Yaskawa Electric Corporationas an Engineer in the Motor Design Division. Heserved as a Motor Design Engineer and a PositionSensor Design Engineer for motor drives. He wastransferred to Yaskawa America, Inc., Waukegan, IL,USA, in 2011 and remained there until May 2013.He then became a Research Engineer in the Energy

Conversion Technology Division of Yaskawa Electric Corporation.

Yifeng Wu (M’98) received the Ph.D. degree fromthe University of California, Santa Barbara, CA,USA, in 1997 with a thesis on GaN power high-electron-mobility-transistors.

He served as a Lead Scientist for GaN microwaveand millimeter-wave power devices at WideGapTechnology LLC and Cree Inc. for 11 years. Hejoined Transphorm Inc., Goleta, CA, USA, in 2008and is currently Vice President of Product Develop-ment and Applications. He has made sustained con-tributions to GaN microwave and power electronics.

He extended the power density records of microwave transistors multiple times,holds 47 patents, and authored many high-impact papers resulting in more than5000 citations in Google Scholar.

Don Kebort received the A.A. degree from LincolnTechnical Institute in 2000.

He joined the application development group atTransphorm Inc., Goleta, CA, USA, in 2010, wherehe is primarily focused on showcasing Transphorm’sGaN power technology in motor drive applications.His prior experience consists of circuit design andembedded firmware development for the optical tele-com industry, working for a series of start-up com-panies in Santa Barbara, CA, USA, as well as JDSUniphase, Milpitas, CA, USA.

Jim Honea received the B.S. and M.S. degreesin electrical engineering from the University ofArkansas Fayetteville, AR, USA, in 1981 and 1986,respectively, and the Ph.D. degree in electrical andcomputer engineering from the University of Cali-fornia, Santa Barbara, CA, USA, in 2011.

Since 2007, he has been working in applica-tions engineering at Transphorm Inc., Goleta, CA,USA, developing applications of high-voltage GaNHEMTs for power conversion. Previously, he heldpositions in design engineering and engineering

management for Topcon Positioning Systems and for Topcon-Sauer-DanfossIntegrated Controls, and in IC design for General Electric.

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