電気学会論文誌●（●●●●●●●部門誌）
IEEJ Transactions on ●●●●●●●●●●●●●●●
Vol.●● No.● pp.●-●
DOI: ●.●●/ieejeiss.●●.●

Paper
Experimental Verification of EMC Filter Used
for PWM Inverter with Wide Band-Gap Devices
Jun-ichi Itoh＊a), Member,

Takahiro Araki＊, Member,

Koji Orikawa＊, Member(Manuscript received Jan. 00, 20XX, revised May 00, 20XX)
This paper discusses the volume of an electromagnetic compatibility (EMC) filter and a cooling system that are used for apulse width modulation (PWM) inverter with wide band-gap devices. First, the volume of reactors that are used in EMC filterssuch as common mode choke coils and differential mode choke coils is theoretically estimated. Then, the relationship between
the carrier frequency of the PWM inverter and the total volume of filter reactors is clarified via simulation. Moreover, therelationship between the carrier frequency and the volume of the cooling system is calculated on the basis of on experimental
results. The total volume of the inverter system that contains the filter reactors and cooling systems is reduced by 54% at a carrier
frequency of 300 kHz using a two-stage filter, as compared to the case of a carrier frequency of 150 kHz with a single-stage filter.
In addition, an induction motor is driven by a prototype GaN-FET inverter system having a carrier frequency of 300-kHz. As aresult, the conducted emission is suppressed below the limit prescribed by CISPR-11 Group 1. Therefore, the proposed design
method for EMC filters is validated experimentally. Furthermore, the power loss of the EMC filter is less than 2% as comparedwith the total loss of the GaN-FET inverter system.
Keywords : EMC filter, high-frequency switching, PWM inverter, wide band-gap devices

regulations such as CISPR (International special committee onradio interference). In order to suppress the noise which is emitted
from the PWM inverter, the EMC filter that is constructed bypassive components such as an inductor and a capacitor are added
to the input of the inverter system. In addition, the PWM inverter
becomes smaller due to the high performance switching device
and developments of cooling techniques. Thus, the volume of the
EMC filter must be considered in order to miniaturize the inverter
system.
The volume of the EMC filter is determined by the attenuation
rate and the frequency of the noise. The noise that is emitted fromthe PWM inverter is varied by the carrier frequency. Therefore,
the EMC filter is miniaturized when the carrier frequency is higher
and higher. In contrast, the switching loss is increased by the highcarrier frequency. Consequently, the cooling system becomeslarger. Therefore, the volume of the cooling system must be
considered for minimizing the EMC filter under a high frequency
switching operation. Although the EMC filter design method arereported at the constant carrier frequency [13-14], it seems that therelationship between the power converter volume and the carrier
frequency has not been discussed concretely through theexperiments in past works.
This paper discusses the relationship between the carrier
frequency and the total volume of the inverter system based on
simulation and experiments using GaN-FET. CISPR prescribes thelimited value of the EMI emitted from information technology
equipment and industrial, scientific and medical equipment and soon and measurement method of it. In this paper, the prototype
circuit of a PWM inverter using GaN-FET is assumed to be used
as industrial equipment in CISPR Group 1. Therefore, it will beshown that the EMI emission of the prototype circuit is satisfied
the standard of CISPR-11 Group 1.
In particular, CISPR-11 Group 1 does not prescribe the limited

1. Introduction
Recently, fast-switching and low on-state voltage drop are
required for power conversion circuits in order to reduce thepower loss. However, silicon based switching devices such as
Si-MOSFETs and Si-IGBTs, are difficult to achieve a significant
performance improvement because those devices’ performance isalmost reaching the limit that derived from the physical propertiesof silicones. On the other hand, switching devices based on a wideband-gap semiconductor such as gallium nitride (GaN) or siliconcarbide (SiC) has been studied in recent years [1-3]. Those wideband-gap devices can perform fast-switching and features low
on-state voltage drop compared with normal silicon devices under
the high temperature operation.
One of problems of the wide band-gap device is cost. However,
it is expected that the wide band-gap devices are used for general
power converter. Power conversion circuits with wide band-gap
devices have been studied in order to achieve an high efficiency ina high temperature operation[4-12]. However, it seems that theperformance and the miniaturization effect are not discussed inprevious studies.
Authors have been focused on the volume of an EMC filter for
PWM inverters. The PWM inverter can control the output voltage
and output frequency by using switching devices. However, thenoise occurs at the switching of the switching device because thevoltage and current are changed rapidly. Recently, this noise
becomes larger because the fast switching devices such as wideband-gap devices are applied to the PWM inverter in order toreduce the switching loss. The noise may cause a false operationof surrounding control systems. Hence, it is limited by somea) Correspondence to: Jun-ichi Itoh. E-mail: itoh@vos.nagaokaut.ac.jp＊
Nagaoka University of Technology
1603-1, Kamitomioka-machi, Nagaoka city, Niigata, Japan 940-2188© 200● The Institute of Electrical Engineers of Japan.

1

EMC Filter for Inverter with Wide Band-Gap (Jun-ichi Itoh et al.)value of the EMI in the frequency of 9 kHz – 150 kHz. On theother hand, when the rated input power is below 20 kVA in
specific, the limited value of the EMI in the frequency of 150 kHz– 500 kHz is 79 dBV. Moreover, the limited value of the EMI in
the frequency of 500 kHz – 30 MHz is 73 dBV. Spectrums oflow frequency components of the limit of CISPR-11 Group 1
which is from 150 kHz to 30 MHz can be reduced by increasing
the carrier frequency using GaN-FET. As a result, the noise of the
low frequency components which have to be suppressed by the
EMC filter can be reduced. Therefore, the size of EMC filter canbe downsized by increasing the carrier frequency. At first, thepower loss and the volume estimation method of the inverter
system is mentioned. Second, the design method of the multi-stage
EMC filter is clarified. Then, the relationship between the carrier
frequency of the PWM inverter and the volume of filter reactor isclarified by simulations, besides the relationship between the
carrier frequency and the volume of a cooling system. At last, a
prototype of GaN-FET inverter is demonstrated by experiments
using an R-L load and an induction motor. The power loss andconducted emissions of the prototype system are shown. As aresult, it is confirmed that the total volume of GaN-FET inverter
system can be reduced to 54% at the carrier frequency of 300 kHz
by using a two-stage filter the case of the carrier frequency of 150
kHz by using a single-stage filter.

Vin
EMC
filter

Si-Diode
Rectifier

2.1 Power loss of switching devices
Fig. 1 shows thesystem configuration of the PWM inverter with GaN-FET. The
switching loss of each device PSW is calculated by (1) [15].



Load

GaN-FET
InverterFig. 1. Circuit configuration of three phase PWM inverter
that is constructed by GaN-FET.
Table 1. Simulation parameters that is used fordesigning the EMC filter and cooling system.
Input voltage Vin
200 V
Input frequency fin
50 Hz
DC link voltage VDC
282 V
Output voltage Vout
173 V
Output current Iout
1.9 A
Output frequency fout
50 Hz
Load impedance Zload
53 
0.99
Power factor cos1
Modulation ratio 
CSPI
3
On-resistance RON
100 m
Dead time Td
100 nsAmbient temperature Ta
20 ℃
Junction temperature Tj
100 ℃
Load factor k
0.1
Lead angle 
10/180 rad
Leakage current Ileak
1 mA

2. Volume estimation method

PSW 

VDC



VDC I meon  eoff f carrier .............................. (1)4VDCd I md

From grid
LC1

where fcarrier is the carrier frequency, VDC is the DC link
voltage, Im is the maximum output current, eon and eoff
are turn on and turn off energy of each switching, and
VDCd and Imd are the voltage and current that aredescribed on a datasheet for measuring the switchingtime.
Table 1 shows the simulation parameters that are used for adesign of the EMC filter and the cooling system.
The total power loss generated in the switching devices Ploss
which be composed of the conduction loss and the switching loss,
is calculated by (2).

LD1

CX1

CXn

CY1
1

To rectifier
LDn

LCn

2

CYn
n

Fig. 2. Circuit schematics of multi-stage EMC filter.
The volume of the cooling system volcooling is given by (3) [16].

vol cooling 2IPloss  6PSW  PCON   6 PSW  m RON  ..................... (2)
2



Ploss
1
................... (3)Rth  CSPI T j  Ta  CSPI

where Rth is the thermal resistance of the coolingsystem, Tj is the junction temperature of the switching
device, and Ta is the ambient temperature.
2.3
Design method of multi-stage EMC filter
Fig. 2shows the circuit schematics of a multi-stage EMC filter. In thispaper, the multi-stage EMC filter is constructed by connecting thesingle-stage EMC filter in series. Each filter that has different
number of stages is designed in order to get a same attenuation. In
addition, the capacitance of X capacitors and Y capacitors are
divided equally for all stages.
At first, the X capacitor that suppresses fluctuations of the input
voltage is designed by (4) using an allowable lead angle of input
current  because it reduces the power factor at the light load.

where RON is the on-state resistance of the GaN-FET.
2.2 Volume of cooling systems
The PWM inverter
needs a cooling system such as heat sinks and fans because theswitching devices are heated by the switching loss and the
conduction loss. Generally, the cooling system is designed basedon a thermal resistance. However, the thermal resistance depends
on its volume. Therefore, the CSPI (Cooling System Performance
Index) is introduced in order to estimate the volume of coolingsystems. The CSPI indicates the cooling performance per unit
volume of the cooling system which is a reciprocal of the productof the volume and the thermal resistance. It means that a highperformance cooling system shows high CSPI. Therefore, thecooling system is miniaturized when the CSPI becomes higher.
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IEEJ Trans. ●●, Vol.●●, No.●, ●●●EMC Filter for Inverter with Wide Band-Gap (Jun-ichi Itoh et al.)

3kI in 1  cos  2.......................................... (4)nVin cos 

C Xn Vin
LISN

where k is the load factor (the output power/themaximum power), Iin is the input current, n is thenumber of filter stage,  is the input angular frequency,
and Vin is the input voltage.
If the lead angle of the input current  is small, (4) is simplified
as (5).

C Xn 

3 I leak................................................................ (6)nVinFinally, the inductance of differential mode choke coils LDn andcommon mode choke coils LCn are designed by (7) in order tosuppress the conducted emission below the limit of CISPR-11
Group 1. Also, the common mode noise and the differential modenoise are separated in order to evaluate the each noise [17].

1 Att2C Xn,Yn Att

1
n



1



2
Att





1

..... (7)C Xn,Yn G0  G f n

where Att is the designed cut-off frequency of the LC
filter, Att is the attenuation of the EMC filter, G0 is thepeak value of the conducted emission without the EMC
filter, and Gf is the limit of CISPR-11 Group 1.
2.4
Volume of EMC Filter
According to (5) and (6),the capacitance of X capacitor and Y capacitor is not changed by
the carrier frequency. Also, the total capacitance is same
regardless of the number of EMC filter stages. Therefore, thevolume of those capacitors is not considered.
On the other hand, the reactor volume is changed significantly
by the parameter of the component. There are several ways toselect the core for the reactor. In this paper, the reactors aredesigned by the Area Product concept [18] using a window area
and a cross-sectional area of the core. Therefore, the volume of thereactor volL is given by (8).

3. Volume evaluation of inverter
3.1 Simulation conditions
Fig. 3 shows the conductedemission evaluation system. Capacitors are added between theswitching devices and a FG, and the output voltage midpoint andthe FG in order to model the stray capacitances of a general
inverter [14]. In this paper, a modeled Line Impedance Stabilizing
Network (LISN) and a spectrum analyzer are used in order toestimate the conducted emission by the simulation [19].
3.2 Experimental conditions
Table 2 shows the circuit
parameters on experiments. The GaN-FETs (VDSmax = 600 V, IDmax= 10 A, RON = 100 m) are used for the PWM inverter in order toachieve high frequency switching, and the Si-diodes are used as arectifier part to evaluate the conducted emission generated by the
inverter unit. The PWM inverter is controlled by V/f control.
PWM signals are generated by comparing the triangle wave andthe output voltage command. The conducted emission generated
by control circuit is deducted in order to evaluate the conductedemission of the inverter.
3.3 Volume of filter reactor
Table 3 shows thecalculation conditions for volume of filter reactor. The total
volume consists of the differential mode choke coils and thecommon mode choke coils is calculated by (7), (8) and (9).
Fig. 4 shows the relationships between the number of filter
stage and the total volume consists of the differential mode chokecoils and the common mode choke coils if the carrier frequency of
PWM inverter is 300 kHz. The volume of filter reactors for thecase of a single EMC filter is used as a standard volume regardlessof the attenuation of EMC filter. In addition, the volume of X
capacitors and Y capacitors are assumed as same regardless of thenumber of filter stages because the total capacitance of each filter

3 2W  4
 .................................................. (8)vol L  K v 
 K u Bm J 
where Kv is the constant value depending on the shapeof cores, W is the maximum energy of the reactor, Ku is
the occupancy of the window, Bm is the maximum flux
density of the core, and J is the current density of thewire.
The maximum energy of the reactor W is given by (9).

W

PWM
inverter

Stray capacitance

3kI in.............................................................. (5)nVin

LDn ,Cn 

DiodeRectifierFig. 3. Conducted emission evaluation systemused in simulation.
Table 2. Experimental conditions to measure the power loss of
GaN-FET inverter with RL load.
Input voltage Vin
100 V
Input frequency fin
50 Hz
DC link voltage VDC
140 V
1Modulation ratio Output frequency fout
20 Hz
Load impedance Zload
51 
0.99
Power factor cosAmbient temperature Ta
25 ℃
Dead time Td
100 nsMaximum drain-source
600 V
voltage VDSmax
Maximum drain current IDmax
10 A
On state resistance RON
100 m
Table 3. Calculation conditions for volume of filter reactor.
Parameters
For LDn
For LCn
Kv
82.7
16.3
Ku
0.2
Bm
0.4 T
J
4 A/mm2

Second, the Y capacitor that bypasses the common modecurrent is designed by (6) based on the acceptable leakage current
Ileak.

CYn 

RL loadEMC
filter1
2
LDn ,Cn I LDnp ,LCnp ................................................. (9)2where ILDnp is the maximum current of the differential
mode reactor, ILCnp is the maximum current of thecommon mode reactor.

3

IEEJ Trans. ●●, Vol.●●, No.●, ●●●EMC Filter for Inverter with Wide Band-Gap (Jun-ichi Itoh et al.)Volume of filter reactor [%]is same. Owing to this, the EMC filter becomes smallest if thevolume of filter reactor is smallest by selecting the suitable
number of filter stage.
According to Fig. 4, the filter reactor becomes smallest for thecase of the two-stage filter is applied if the attenuation of filter is
30 dB. On the other hand, the single-stage filter is smallest if theattenuation of filter is 10 dB. Moreover, the three-stage filter is thesmallest if the attenuation of filter is 50 dB. Consequently, thenumber of filter stage that achieve smallest filter is decided by therequired attenuation of the filter.
Fig. 5 shows a relationship between the carrier frequency andthe volume of filter reactor. The volume of filter reactor for thecase of single EMC filter and 150 kHz-carrier frequency is used asa standard volume.
According to Fig. 5 (a) and Fig.5 (b), the volume of differential
mode choke coil and common mode choke coil are reduced byhigh carrier frequency because the attenuation of LC filter is large
at the high frequency region. In addition, the filter reactor
becomes smaller regardless of the number of filter stages. As iswell known, from 150 kHz to 30 MHz of conducted emission islimited by CISPR-11 Group 1. That is, the carrier frequency ismatch to the lowest frequency of limited band if the carrier
frequency is 150 kHz. In other words, the filter reactor becomeslargest if the carrier frequency is 150 kHz.
Besides, the choke coils of multi-stage filters are miniaturizedcompared with the single-stage filter. If the number of filter stage
is increased from one to two, the volume of filter reactor becomes
half when the carrier frequency is 150 kHz. Downsizing of EMC
filter using the multi-stage filter can achieve high efficiency
because the switching loss does not increase due to without theincreasing of the carrier frequency. On the other hand, thecomponents that construct the EMC filter such as choke coils andcapacitors are increased in proportion to the number of filter
stages. Because of this, the two-stage filter is smaller comparedwith three-stage filter.
The volume of filter reactor is almost same regardless of thenumber of filter stages when the carrier frequency is 600 kHz. In
this case, the filter reactor is not miniaturized by using themulti-stage filter because filter reactor is already downsized byhigh carrier frequency. Thereby, the multi-stage filter is notsuitable because number of components of the multi-stage filter isincreased when the carrier frequency is 600 kHz.
3.4
Loss analysis results
Fig. 6 shows the power loss
that is measured from the GaN-FET inverter. The maximum
efficiency is 94.7% when the carrier frequency is 150 kHz.
The conduction loss is given by y-intercept of approximate
formula b because it is not related to the carrier frequency. On theother hand, the switching loss of PWM inverter is given by slopeof approximate formula. From experimental results, theconduction loss and the switching loss on arbitrary output poweris calculated by (10) and (11)VDC _ test I out _ test

200

Att = -30dB

100

Att = -50dB
2

3
4
Number of filter stages n

5Volume of filter reactor [p.u.]

1.0Volume of filter reactor [p.u.]

Fig. 4. The relationships between the number of filter stage andvolume of filter reactor.

1.0

1p.u.=0.0433 dm3 at fcarrier=150kHz, single stage

0.8
Three stages

0.6
0.4

Single stage

0.2 Two stages
0
150

300
450
Carrier frequency [kHz]600(a) Differential mode choke coil

1p.u.=0.293 dm3 at fcarrier=150kHz, single stage

0.8
0.6

Three stages

0.4
0.2

Single stage
Two stages

0
150

300
450
Carrier frequency [kHz]600(b) Common mode choke coilFig. 5. Volume of filter reactor.
14

Total power loss [W]Ptotal=1.47×10-5fcarrier+4.67
12
10
8
6
150

300
450
Carrier frequency [kHz]600

Fig. 6. Measurement result of relationship between
carrier frequency and power loss of GaN-FET inverter.
power loss is experimentally measured.
Fig. 7 shows the power loss analysis results of the GaN-FET
inverter based on experimental results. The conduction loss islarger than the switching loss when the carrier frequency is 150
kHz. However, the switching loss becomes larger if the carrier
frequency is higher than 300 kHz. In other words, the switchingloss has an insignificant effect on the total power loss in the low
carrier frequency region. Consequently, the proposed system candownsize the EMC filter without increasing of the volume ofcooling systems in the low carrier frequency region. Therefore, the2

VDC _ calc I out _ calc

400

01

I

PCON  b   out _ calc  ............................................... (10)
 I out _ test PSW  af carrier

fcarrier=300 kHz Attenuation of filter Att = -10dB................................... (11)where Iout_calc is the output current on the arbitrary
output power, and Iout_test is the output current when the
4

IEEJ Trans. ●●, Vol.●●, No.●, ●●●EMC Filter for Inverter with Wide Band-Gap (Jun-ichi Itoh et al.)PWM inverter that can achieve the low switching loss is suitablefor proposed system.
The ratio between the switching loss and the conduction loss of
PWM inverter depends on the characteristics of switching devices.
Thus, the GaN-FET is suitable for the proposed system because it
can perform fast switching and low switching loss.
Fig. 8 shows the calculation result of the power loss if theinverter outputs the rated power of 750 W. In this case, theconduction loss accounts more portions in the total loss when the
carrier frequency is 150 kHz because the conduction loss is
proportional to the square of the output current. On the other hand,the switching loss accounts more portions in the total loss when
the carrier frequency is higher than 450 kHz.
Fig. 9 shows the relationship between the carrier frequency andthe volume of cooling systems. The volume of cooling system iscalculated by (3) based on experimental results. The coolingsystem becomes large at the high frequency region.
3.5
Power density of GaN-FET inverter
Fig. 10shows the relationships between the carrier frequency and the total
volume of the inverter system that contains filter reactors andcooling systems. The volume of other components is not included
because it does not depend on the carrier frequency. According to
Fig. 10, the inverter system is miniaturized by high frequency
switching because the volume filter reactors are decreased sharply.
On the other hand, the cooling system is larger when the carrier
frequency is higher than 300 kHz. Moreover, the volume ofinverter system is reduced by using a multi-stage filter because theattenuation of LC filter is significantly increased. As a result, thetotal volume of GaN-FET inverter system will be reduced by 54%
at the carrier frequency of 300 kHz by using a two-stage filter
compared to case of the carrier frequency of 150 kHz by using asingle-stage filter.
Fig. 11 shows the relationship between the carrier frequency
and the power density of the inverter system. It means that highefficiency and small inverter system shows high power density. In
this paper, the power density power is defined as (12) by using the
rated power of PWM inverter Pout and the total volume of inverter
system voltotal that contains filter reactors and the cooling system.

Power loss [%]

12

9
6

Switching loss

3
Conduction loss
0

150

300
450
Carrier frequency [kHz]600

Fig. 7. Breakdown of power loss of GaN-FET inverter
based on experimental results.
6Power loss [%]Rated power of inverter:750W=100%
4

Conduction loss
2

Switching loss

0
150

300
450
Carrier frequency [kHz]600

Volume of cooling system [p.u.]

Fig. 8. Calculation result of relationship between
carrier frequency and power loss of GaN-FET inverter.

P power  out .......................................................... (12)
vol total

2.0
1p.u.=0.138 dm3 at fcarrier=150kHz
1.8
1.6
1.4
1.2
1.0
150

300
450
Carrier frequency [kHz]600

Fig. 9. Relationship between carrier frequency
and volume of cooling system.

The power density is inverse proportion to the total volume ofthe system. Therefore, the power density becomes the highest at
the carrier frequency of 300 kHz.
Similarly, the power density becomes highest if the two-stage
filter is applied to the inverter system. In this system, the power
density is insignificantly changed even if the carrier frequency
becomes higher because the EMC filter is already downsized. In
other words, the downsizing of the EMC filter by high frequency
switching is most effective if the single-stage filter is applied.
Generally, the design of multi-stage filter is complicated owing to
the increasing of components. Therefore, the design of EMC filter
becomes easier if the single-stage EMC filter is miniaturized byhigh frequency switching.
Fig. 12 shows Pareto front curves of the GaN-FET inverter at
the range of carrier frequency from 150 kHz to 600 kHz. The
Pareto front curves are used for determining the optimum point inorder to achieve many objectives. The horizontal axis in Fig. 12
indicates the power density, and the vertical axis in Fig. 12
indicates the efficiency of the GaN-FET inverter. Therefore, theinverter system can achieve high efficiency and the smaller size if
the Pareto front curve comes close to top right of the graph.
According to results, the EMC filter should be constructed by a
two-stage filter in order to achieve high power density and highefficiency. In addition, the power density becomes highest at thecarrier frequency of 300 kHz, and the efficiency of the GaN-FET
inverter becomes highest at the carrier frequency of 150 kHz.
3.6
Measurement results of conducted emission
Fig.
13 shows the conducted emission of the PWM inverter with
GaN-FETs. A resistance and an inductance are connected to the
output of the inverter system as a load. First, the validity of thedesign method of EMC filters is proved if the load is R-L loads.
This is because it is easy to demonstrate stray capacitance between
the R-L load and the ground while it is difficult to estimate stray
capacitance between a motor and the ground. Also, the EMC filterin this section is designed according to the design method which is
mentioned in the section 2.3. The red line indicates the limit of
CISPR-11 Group 1. It is noted that the carrier frequency is 300
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IEEJ Trans. ●●, Vol.●●, No.●, ●●●EMC Filter for Inverter with Wide Band-Gap (Jun-ichi Itoh et al.)

80

1.0

Limit of CISPR

Conduction noise [dBV]

Total volume [p.u.]

1p.u.=0.474 dm3 at fcarrier=150kHz, single stage
0.8
Three stages
0.6

Single stage

0.4
150

Two stages
300
450
Carrier frequency [kHz]600

Fig. 10. Relationship between carrier frequency
and total volume of GaN-FET inverter system.

60

40

20
0

0.15

0.3

0.5

1
3
5
Frequency [MHz]

30

80

10

30

Limit of CISPR

3Three stages

2
Single stage
1
150

300
450
Carrier frequency [kHz]600

Fig. 11. Relationship between carrier frequency
and power density of GaN-FET inverter.
96

Single stage

94

60
40

20

0

0.15

Three stages
Two stages

95 fcarrier=150kHz
Efficiency [%]10(a) Two-stage filter.

Two stages

Conduction noise [dBV]

Power density [kW/dm3]

4

0.3

0.5

1
3
5
Frequency [MHz](b) Single-stage filter.

Fig. 13. Conducted emission of the GaN-FET inverter
using 300 kHz carrier with designed EMC filter.

fcarrier=300kHz

150kHz-600kHz

93

fcarrier=450kHz

6

Vin

92
91
1

Control
circuitVref

fcarrier=600kHz
2
3
Power density [kW/dm3]

LISN

4

EMC
filter

Diode
Rectifier
HeatSink

Fig. 12. Pareto front curve of GaN-FET inverter.
(Relationship between power density andefficiency of GaN-FET inverter)

VDC

PWM
inverterIM

HeatSink

Fig. 14. Experimental configuration
when induction motor is driven by GaN-FET inverter.
Table 4. Experimental condition.
Input voltage Vin
200 V
Input frequency fin
50 Hz
DC link voltage VDC
280 V
Output voltage Vout
173 V
Output frequency fout
43 Hz
Modulation factor
1
Dead time TD
100 nsCommon mode reactor LC
700 H

kHz. In Fig. 13 (a), the two-stage filter is connected to the input of
the inverter system. As a result, the conducted emission issuppressed below the limit of CISPR-11 Group 1. Therefore, theproposed design method for EMC filters is valid in theexperiment.
Fig. 13 (b) shows the conducted emission when the single-stage
EMC filter is applied to the inverter system. In the low frequency
region, the conducted emission is suppressed below the limit of
CISPR-11 Group 1 as same as the two-stage filter. Especially, theconducted emission at 300 kHz is almost same between Fig. 13 (a)and Fig. 13 (b). It means the attenuation of the single-stage filter
and the multi-stage filter is same at the designed frequency of thefilter. Therefore, the proposed design method of EMC filters is
valid regardless of the number of filter stage. On the other hand, at
9 MHz, the conducted emission is over the limit of CISPR-11
Group 1. That is because the attenuation of the single-stage filter

is smaller than that of the multi-stage filter at the high frequency
region.

4. Motor drive experiment
Next, the experiment of an induction motor is conductedbecause expected applications of the prototype system areassumed to be used for motor drive systems.
6

IEEJ Trans. ●●, Vol.●●, No.●, ●●●EMC Filter for Inverter with Wide Band-Gap (Jun-ichi Itoh et al.)

4.1
Experimental condition
Fig. 14 shows thesystem configuration when an induction motor is driven by the
GaN-FET inverter. The ground terminal of EMC filter and theinduction motor are connected to the ground terminal of the LISN.
Similarly, the heat sink of the GaN-FET inverter is connected to
the LISN.
Table 4 shows the experimental condition. In this condition, thedesigned value of the differential mode choke coil is smaller thanthe leakage inductance of common mode choke coil. Thereby, thedifferential mode choke coil is assumed as a leakage inductance ofthe common mode choke coil.
4.2
Experimental results
Fig. 15 shows the power
loss of the prototype inverter system. It is noted that the power
loss of GaN-FET inverter that is proportion to the carrier
frequency is defined as the switching loss. Also, the power loss
that is not proportion to the carrier frequency is defined as the
conduction loss.
From the experimental results, the efficiency of the GaN-FET
inverter is low. That is because the power factor is low due to thedrive of the induction motor by V/f control at no load. In contrast,
the power loss of EMC filter is less than 2% compared with thetotal loss of the GaN-FET inverter system.
Fig. 16 shows the conducted emission when the induction
motor is driven by the GaN-FET inverter. From the result, theconducted emission is suppressed below the limit of CISPR-11
Group 1. Therefore, the proposed design method for EMC filters
is valid in the experiment regardless of the load of the inverter
system.
In addition, the conducted emission in the low frequency region
is increased compared to the Fig. 13 (a) because the DC voltage ofthe inverter system is high. Hence, the noise generated by theswitching becomes larger. Moreover, the conducted emission
around 9 MHz is decreased because a parasitic capacitance of theload is changed compared to the R-L load.
From Figs. 13 and 16, it is obvious that the attenuation of the
EMC filter against the EMI in the frequency of 30 - 300 MHz is
weakened. This is because the effect of parasitic parameters islarge against the EMI in the frequency of 30 - 300 MHz. On theother hand, high carrier frequency reduces the volume ofcomponents of the EMC filter. As a result, high carrier frequency
can reduce not only the whole volume of the EMC filter but also
values of parasitic parameters. However, the purpose of this paper
is that the clarification of the carrier frequency which achieves theminiaturization of the total volume includes the inverter and the
EMC filter considering the EMI in the frequency of 150 kHz -30
MHz. Therefore, high carrier frequency which can reduce thevalue parasitic parameters against the EMI in the frequency of 30 300 MHz is not treated in this paper. In addition, the design
method of the EMC filter which considers the parasitic parameters
is not mentioned. However, it is important to consider the parasitic
parameters in order to design the EMC filter precisely.

40

Others

Input power=103W at fcarrier=150 kHz

Power loss [%]Filter loss
30
Rectifier loss
20
Switching loss
10
Conduction loss
0

150

300
450
Carrier frequency [kHz]600

Fig. 15. Power loss of prototype inverter system
when induction motor is driven by V/f control.

Conduction noise [dBV]

80

Limit of CISPR

60

40

20

0
0.15

0.3

0.5

1
3
5
Frequency [MHz]1030

Fig. 16. Conducted emission of the prototype inverter
system with induction motor.
In addition, an induction motor was driven by the prototype of
GaN-FET inverter system with the carrier frequency of 300 kHz.
As a result, the conducted emission was suppressed below thelimit of CISPR-11 Group 1. Therefore, the proposed design
method for EMC filters was valid in the experiment. Furthermore,
the power loss of the EMC filter is less than 2% compared withthe total loss of the GaN-FET inverter system.
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(2)

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5. Conclusion(5)This paper discussed the relationship between the carrier
frequency and the total volume of the GaN-FET inverter system
based on experiments. As a result, the total volume of the
GaN-FET inverter system that contains an EMC filter and acooling system will be reduced by 54% at the carrier frequency of
300 kHz by using a two-stage filter compared to case of the carrier
frequency of 150 kHz by using a single-stage filter.

(6)

(7)

7

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Koji Orikawa(Member) received the M.S. and Ph.D. degrees inelectrical,
electronics
andinformationengineering from Nagaoka University ofTechnology, Niigata, Japan, in 2010 and 2013
respectively. Since 2013, he has been working at
Nagaoka University of Technology as a
postdoctoral fellowship. He is a member of theInstitute of Electrical Engineers of Japan and theInstitute of Electrical and Electronics Engineers.
His research interests include power conversion system especially
DC-DC converters and high frequency techniques for power converters.

Jun-ichi Itoh

(Member) received his M.S. and Ph.D. degrees inelectrical and electronic systems engineeringfrom Nagaoka University of Technology, Niigata,Japan in 1996 and 2000, respectively. From 1996
to 2004, he was with Fuji Electric Corporate
Research and Development Ltd., Tokyo, Japan.
Since 2004, He has been with Nagaoka
University of Technology as an associate
professor. He received the IEEJ Academic
Promotion Award (IEEJ Technical Development Award) in 2007 andthe Isao Takahashi Power Electronics Awar d in 2010. His researchinterests include matrix converters, DC/DC converters, power factor
correction techniques and motor drives. He is a member of the Instituteof Electrical Engineers of Japan and the Society of Automotive
Engineers of Japan.
Takahiro Araki(Member) received his B.S. and M.S. degrees inelectrical,
electronics
andinformationengineering from Nagaoka University ofTechnology, Nagaoka, Japan in 2012 and 2014,
respectively. Since 2014, he is with Hitachi Ltd.,
Ibaraki, Japan. His research interests include
evaluations of EMC filters used for PWM
inverters with wide band-gap devices. He is amember of the Institute of Electrical Engineers ofJapan.
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IEEJ Trans. ●●, Vol.●●, No.●, ●●●