Elec omagne ic Emissions Mechanisms below
30 MHz in High Vol age Powe Swi ching
Abs ac — This s udy in es iga es elec omagne ic emissions
mechanisms below 30 MHz due o high ol age swi ching o powe
de ices. The ela ionship be ween conduc ed and adia ed
emissions is discussed. A p o o ype buck con e e wi h a
300 A / 1200 V IGBT module is used o analyze swi ching beha io
a swi ching speeds om 1.5 kV/μs o 28 kV/μs, using ime-domain
measu emen me hods. I is ound ha swi ching beha io a ec s
bo h conduc ed and adia ed emissions, pa icula ly om 10 MHz
o 30 MHz. Fu he mo e, adia ion mechanisms o he buck
con e e a e expe imen ally analyzed by changing i s
con igu a ions. The esul s show ha he buck con e e exhibi s
an inciden al adia ed emission mechanism in ol ing he
p o ec i e ea h cable, which ac s as a monopole an enna due o
po en ial luc ua ions ela i e o he g ound. The mechanism,
which bypasses he con en ional common mode emission pa h,
deg ades he e ec i eness o choke coils and il e s.
Keywo ds — Elec omagne ic emissions, IGBT, adia ion
mechanism, swi ching beha io .
I. INTRODUCTION
In ecen yea s, he demand o high powe semiconduc o
modules used in powe con e sion equipmen , widely used in
ields such as indus ial applica ions, au omo i e and
anspo a ion sys ems, and elec ici y sys ems, has inc eased
signi ican ly. Insula ed Ga e Bipola T ansis o s (IGBTs) a e
commonly used in hese applica ions due o hei eliabili y and
e iciency. Howe e , as powe elec onics applica ions expand,
elec omagne ic in e e ence (EMI) has eme ged as a c i ical
conce n in hese ields. Va ious in e na ional s anda diza ion
o ganiza ions ha e de eloped elec omagne ic compa ibili y
(EMC) s anda ds o con ol EMI wi h emission limi s. Such
s anda ds, including he IEC 61800-3 [1] o powe d i e
sys ems, speci y limi s o conduc ed emissions in he
equency anges om 9 kHz up o 30 MHz, and o elec ic
adia ed emissions abo e 30 MHz. Recen ly, he In e na ional
Elec o echnical Commission (IEC) has ini ia ed discussions on
he s anda diza ion o equi emen s o magne ic adia ed
emissions below 30 MHz o gene al powe elec onic
equipmen [2]. Consequen ly, u u e EMI equi emen s o
powe elec onics equipmen migh become s ic e .
To supp ess he EMI, p e ious esea ch has ocused on il e
design [3] and he pa asi ic capaci ance o powe de ices [4].
Addi ionally, p e ious esea che s ha e in es iga ed he
ela ionship be ween swi ching beha io and EMI using
ma hema ical [5] and expe imen al me hods [6], [7]. These
in es iga ions ocus on conduc ed emissions and he spec um
o swi ching beha io , e ealing how swi ching ansien s
a ec he equency componen s o conduc ed dis u bances and
he op imal swi ching beha io o EMI mi iga ion. Howe e ,
he ela ionship be ween swi ching beha io and adia ed
emissions below 30 MHz emains unclea , and he e is limi ed
co e age in EMC s anda ds in his equency ange.
Fu he mo e, he con e sion mechanism om conduc ed o
adia ed emissions equi es u he in es iga ion.
This s udy analyzes EMI gene a ion mechanisms below
30 MHz using a buck con e e , which ep esen s a
undamen al opology in powe elec onics, as he equipmen
unde es (EUT). The swi ching beha io is con olled by
a ying ga e esis ance (Rg). The ela ionship be ween
conduc ed and adia ed emissions is discussed expe imen ally.
The adia ion pa hs om he buck con e e a e in es iga ed by
changing con igu a ions o he EUT.
The es o he pape is o ganized as ollows: In Sec ion II,
we desc ibe he me hodology o EMI measu emen s, including
he analysis o swi ching beha io . Subsequen ly, Sec ion III
p esen s he analysis esul s o each EMI mode a di e en
swi ching speeds con olled by Rg. Then, he adia ion pa hs
om he buck con e e a e analyzed by changing he
con igu a ion o he EUT. Finally, Sec ion IV summa izes how
swi ching beha io a ec s conduc ed and adia ed emissions
below 30 MHz. The con e sion mechanisms om conduc ed o
adia ed emissions a e examined by measu ing he common
mode cu en o he inpu cable and p o ec i e ea h (PE) cable
o he EUT. The esul s p o ide insigh s in o he adia ion
mechanisms o elec omagne ic emissions below 30 MHz.
II. METHODOLOGY
The EUT is a p o o ype buck con e e including
300 A / 1200 V IGBT module. The con igu a ion o he EUT is
shown in Fig. 1. The buck con e e opology is chosen because
o i s simplici y, which minimizes he in luence o ci cui
complexi y on he expe imen s, allowing he analysis o ocus
di ec ly on he EUT and he cables be ween he EUT and he
powe supply. The load is an induc o o 0.9 mH and is
connec ed in pa allel wi h a F ee Wheeling Diode (FWD). The
Yosuke Saku ai1, Jo di Solé-Llo e as23, Yasu oshi Yoshioka4, Ma co A. Azpú ua23, Rik W. De Doncke 5
1De ice De elopmen Depa men , Semiconduc o s Business G oup, Fuji Elec ic Co. L d., Japan
2EMC Elec omagne ic BCN, S.L., Spain
3G up de Compa ibili a Elec omagnè ica, Uni e si a Poli ècnica de Ca alunya, Spain
4Powe Sys em Con ol Resea ch Depa men , Co po a e R&D Headqua e s, Fuji Elec ic Co. L d., Japan
5Ins i u e o Powe Elec onics and Elec ical D i es, RWTH Aachen Uni e si y, Ge many
{saku ai-yosuke, yoshioka-yasu oshi}@ ujielec ic.com, {jo di.sole, ma co.azpu ua}@emc-ba celona.com
P oc. o he 2025 In e na ional Symposium on Elec omagne ic Compa ibili y (EMC Eu ope 2025), Pa is, F ance, Sep embe 1–5, 2025
swi ching equency o he IGBT, which is connec ed in se ies
wi h he load and FWD, is ixed a 1 kHz. The du y cycle is
adjus ed o main ain a cons an ope a ing cu en du ing es ing.
The basic ope a ing condi ions include an inpu ol age o 600 V,
a collec o cu en (Ic) o 15 A, and a Rg o 23 Ω. To achie e
as e swi ching, he e alua ion is pe o med unde lowe cu en
condi ions han cu en a ing o he IGBT module.
Fig. 1. Buck con e e o EMI measu emen . The buck con e e is connec ed
wi h a 1.5 m inpu cable and a 3 m p o ec i e ea h cable. 0.01–0.1 µF
decoupling capaci o s a he ga e d i e VCC–GND pins a e omi ed o cla i y
bu included in he ac ual ha dwa e. The pa asi ic capaci ance be ween he
swi ching-cell midpoin and PE was no di ec ly measu ed in his wo k. A
de ailed expe imen al cha ac e iza ion will be ca ied ou in u u e wo k.
Measu emen s a e pe o med in a 10 m semi-anechoic
chambe . The measu emen se up is shown in Fig. 2. A Line
Impedance S abiliza ion Ne wo k (LISN) is used o s abilize he
powe supply line impedance and keep he same condi ions o
bo h conduc ed and adia ed emission measu emen s. The inpu
and PE cables o EUT a e connec ed o he powe supply h ough
he LISN. The cables a e bundled and aligned o ace he an enna
wi h he sho es dis ance. The se up main ains a ixed dis ance
o 3 m be ween he EUT and he an enna.
Fig. 2. Measu emen se up o conduc ed and adia ed emissions
measu emen s. The expe imen s a e pe o med inside a semi-anechoic chambe .
This pho og aph shows he an enna o ien ed in he x di ec ion.
To analyze he swi ching beha io o he EUT, he Rg is
adjus ed o modi y he swi ching speed. The swi ching beha io
is shown in Fig. 3. Du ing he u n-on e en , he ga e-emi e
ol age (Vge) inc eases as he con ol signal o he IGBT. The
collec o -emi e ol age (Vce) dec eases, and he collec o
cu en (Ic) s a s conduc ing. The swi ching speed becomes
as e wi h lowe Rg. Du ing he u n-on e en , he uppe a m
FWD ope a es in he opposi e manne as he IGBT. As he
anode-ca hode ol age (Vak) inc eases, he anode cu en (Ia)
dec eases. Compa ing he swi ching ope a ions o IGBT and
FWD, he FWD shows a as e swi ching speed han he IGBT.
Based on his, his s udy ocuses on analyzing he e e se
eco e y beha io o FWD.
The swi ching speed is summa ized in Table . A he highes
swi ching speed o 28 kV/μs, ol age oscilla ions a e obse ed
in he ol age and cu en wa e o ms o he FWD, which is
di ec ly ela ed o an inc ease in elec omagne ic emissions. This
s udy examines emissions, bo h conduc ed and adia ed,
gene a ed by hese swi ching e en s below 30 MHz.
Swi ching condi ions o he EUT. The swi ching speed is con olled
om a e age dV/d o 28 kV/s o 1.5 kV/s by a ying Rg. A e age dV/d is
ob ained om he slope be ween 10 % and 90 % o Vak. Tu n-on loss (Eon) and
e e se eco e y loss (E ) a e calcula ed om cu en and ol age wa e o ms
gi en in Fig.3.
Rg
[Ω]
Re e se eco e y
a e age dV/d [kV/µs]
Eon (Ic = 15 A)
[mJ]
E (Ic = 15 A)
[mJ]
0.7
28
1.83
3.31
10
6
2.78
1.98
23
4
3.48
1.58
50
1.5
4.70
1.20
Fo emission measu emen s, a ime domain measu emen
me hod (shown in Fig. 4) is used ins ead o con en ional
equency-sweep-based spec um analysis [8], [9]. This
measu emen me hod u ilizes ime-domain da a cap u ed by an
oscilloscope and hen is p ocessed using il e s o emula e a
measu ing ecei e . Sho -Time Fou ie T ans o m (STFT) is
applied o ex ac equency in o ma ion. I enables equency
analysis o e speci ic ime in e als, which is use ul o
(a)
(b)
Time [µs]
Time [µs]
x
Fig. 3. Tu n on swi ching e en (a) and e e se eco e y beha io (b) o ou
buck con e e . Swi ching speed is moodula ed wi h a ious Rg.
1
Table 1.
P oc. o he 2025 In e na ional Symposium on Elec omagne ic Compa ibili y (EMC Eu ope 2025), Pa is, F ance, Sep embe 1–5, 2025
Fig. 4. Block diag am o he mul i-channel ime-domain EMI measu emen
sys em used du ing he expe imen s [9].
co ela ing swi ching wa e o ms wi h EMI cha ac e is ics in
his s udy. Addi ionally, he me hod allows o synch onize he
swi ching e en s wi hin he measu emen ime window.
This measu emen me hod u ilizes ime-domain da a
cap u ed by an oscilloscope and hen is p ocessed using il e s o
emula e a measu ing ecei e . STFT is applied o ex ac
equency in o ma ion. I enables equency analysis o e
speci ic ime in e als, which is use ul o co ela ing swi ching
wa e o ms wi h EMI cha ac e is ics in his s udy. Addi ionally,
he me hod allows o synch onize he swi ching e en s wi hin
he measu emen ime window.
III. RESULTS
A. Compa ison o emission modes
Fig. 5 shows he emissions o he EUT unde di e en
condi ions in he equency ange om 9 kHz o 30 MHz. Fi s ,
conduc ed emissions a e analyzed. These emissions a e
classi ied in o wo modes: di e en ial mode and common mode.
Di e en ial mode emissions a e gene a ed by he EUT and low
h ough he posi i e and nega i e sides o he inpu cable in o
he LISN. Common mode emissions low h ough bo h he inpu
and PE cables due o pa asi ic capaci ance be ween he IGBT
chip and he EUT chassis. Di e en ial mode emissions inc ease
signi ican ly be ween 5 MHz and 30 MHz as dV/d inc eases
om 1.6 kV/μs o 28 kV/μs. Common mode emissions emain
unchanged in his equency ange.
Fig. 5. Measu emen esul s o conduc ed and adia ed emissions as a unc ion
o swi ching speed (con olled by Rg).
Nex , he magne ic and elec ic adia ed emissions be ween
5 MHz and 30 MHz show simila equency cha ac e is ics o
he di e en ial mode emissions abo e 5 MHz. Gene ally, ci cui
opology should supp ess adia ed emissions om di e en ial
mode. Howe e , ou indings indica e ha swi ching beha io
a ec s bo h conduc ed and adia ed emissions below 30 MHz,
al hough adi ionally only conduc ed emissions a e conside ed
in his equency ange. These esul s emphasize he impo ance
o conside a ion o adia ed emissions in his equency ange.
B. Analysis o he adia ion sou ce o he buck con e e
To iden i y he adia ion sou ce, magne ic ield adia ion is
measu ed unde di e en con igu a ions as shown in Fig. 6.
Fig. 7 (a) shows EMI measu emen s wi h a ying an enna
o ien a ions. The highes in ensi y is obse ed in he y di ec ion
be ween 10 MHz and 30 MHz, due o he inpu and PE cables
adia ing magne ic ields owa d he an enna.
Fig. 7 (b) shows esul s a e adding a common mode choke
coil o he inpu cable. While in ensi y dec eases below
0.1 MHz, he y di ec ion adia ion be ween 10 MHz and
30 MHz shows minimal change. This esul indica es ha
common mode cu en h ough cable loops o inpu and PE
cable is no he main adia ion sou ce.
Fig. 7 (c) shows he e ec o he PE cable layou . The ed
line indica es esul s when inpu and PE cables a e bundled
oge he , while he blue line shows esul s when hese cables
o m a ho izon al loop wi h a 1 m diame e . Al hough y
di ec ion in ensi y emains s able despi e he la ge loop, x
di ec ion in ensi y inc eases unexpec edly. This indica es ha
adia ion in ensi y depends mo e on he layou o he PE cable
han on loop size.
Fig. 6. Measu emen con igu a ions o analysis o he adia ion sou ce.
Analog Digi al
T1
TN
…
P obe o
T ansduce
CH 1
CH N
EMI
Baseband digi ize
ADC
P e-p ocessing
Memo y
Mul i-domain
Pos -p ocessing
Spec al es ima ion &
EMI de ec o emula ion
Mul i esolu ion
Spec og ams
Wa e o m pa ame e
analysis
S a is ical de ec o s
… … … …
Visualiza ionDa ase s
Re-analysis
EMI1
EMIN
P oc. o he 2025 In e na ional Symposium on Elec omagne ic Compa ibili y (EMC Eu ope 2025), Pa is, F ance, Sep embe 1–5, 2025
(a)
(b)
(c)
(d)
Fig. 7 (d) shows esul s wi hou he PE cable. The adia ion
be ween 10 MHz and 30 MHz is comple ely supp essed. These
esul s iden i y he PE cable as he p ima y adia ion sou ce,
ac ing as an an enna below 30 MHz.
IV. DISCUSSION
Based on ou analysis, swi ching beha io in luences bo h
conduc ed and adia ed emissions below 30 MHz. The
magne ic ield is mainly emi ed om he PE cable, no om
he loop o he inpu cable and PE cable. This sugges s ha
common mode emissions caused by he PE cable a e he main
con ibu o o he emission. Howe e , as shown in Fig. 5, no
signi ican componen s be ween 10 MHz and 30 MHz a e
obse ed in common mode conduc ed emissions. Fu he mo e,
he common mode choke has li le e ec on magne ic ield
mi iga ion.
To cla i y his mechanism, we ca ego ize common mode
cu en componen s, as shown in Fig. 8. The line (a) in Fig. 8
shows he con en ional common mode pa h h ough module
pa asi ic capaci ance and chassis, wi h opposi e cu en low in
inpu and PE cables. The line (b) in Fig. 8 shows a
unidi ec ional cu en om EUT o g ound h ough he PE cable.
Common mode cu en s in he inpu cables (posi i e side
(INpos) and nega i e side (INneg)) and PE cable a e measu ed
using high- equency cu en p obes. The measu emen s a e
implemen ed unde h ee condi ions:
a. The cu en s o INpos and INneg a e measu ed
simul aneously o obse e gene al common mode.
b. The cu en o PE cable is measu ed o obse e bo h
gene al common mode and common mode o g ound
c. INpos, INneg, and PE cable a e measu ed simul aneously o
obse e common mode o g ound, as gene al common
mode is canceled in INpos and INneg.
Fig. 8. De ini ion o common mode cu en be ween he EUT and LISN. Two
common mode pa hs, (a) common mode (gene al) and (b) common mode o
GND a e de ined depending on he cu en pa h.
Fig. 9 shows he spec um o he common mode cu en s in
each cable a as e swi ching unde 15 A, 0.7 Ω condi ion.
10 MHz componen is de ec ed in all common mode cu en s,
pa icula ly in he PE cable, al hough i is no obse ed in he
LISN ol age measu emen s. This equency componen o
common mode cu en s co esponds o he equency
componen o he magne ic and elec ic ield adia ed emissions.
When measu ing cu en s o INpos, INneg, and PE cable
simul aneously, he 10 MHz componen is sligh ly educed
while he 2 MHz componen is signi ican ly educed, indica ing
ha he 10 MHz componen is caused by common mode cu en
o he g ound.
Fig. 9. F equency componen s o common mode cu en o each cable.
Fig. 7. Analysis o adia ion sou ce changing he con igu a ion o he EUT:
(a) an enna o ien a ions; (b) ins alling choke coil o inpu cable; (c) changing
PE cable layou ; (d) PE cable emo al.
P oc. o he 2025 In e na ional Symposium on Elec omagne ic Compa ibili y (EMC Eu ope 2025), Pa is, F ance, Sep embe 1–5, 2025
These esul s indica e ha common mode cu en analysis
p o ides be e insigh s in o he ela ionship be ween conduc ed
and adia ed emissions han ol age measu emen s wi h he
LISN. To analyze he common mode cu en o he g ound in
de ail, he common mode cu en is measu ed bo h nea LISN
and EUT, as shown in Fig. 10. The 10 MHz componen is
negligible nea LISN, indica ing ha common mode emissions
o he g ound a e no cu en dependen . The cu en dis ibu ion
pa e n along he cables shows cha ac e is ics o monopole
an enna s anding wa es, indica ing ha he PE cable emi
adia ed emission as an an enna d i en by po en ial luc ua ions
o he EUT o he g ound. As shown in Fig. 8, hese po en ial
luc ua ions low h ough he module pa asi ic capaci ance and
chassis wi hou passing h ough he inpu cable. Reducing he
pa asi ic capaci ance be ween powe de ice chip and powe
module package is expec ed o mi iga e his emission pa h.
Op imizing swi ching beha io also e ec i ely educes high-
equency componen s o ol age luc ua ions.
Fig. 10. Common mode cu en o each cable depending on measu emen poin ,
nea EUT o nea LISN.
V. CONCLUSION
This s udy in es iga es he ela ionship be ween conduc ed
and adia ed emissions below 30 MHz. While swi ching
beha io adi ionally a ec s conduc ed noise below 30 MHz
and adia ed noise abo e 30 MHz, ou analysis e eals ha
swi ching beha io in luences bo h conduc ed and adia ed
emissions below 30 MHz. Speci ically, IGBT swi ching om
1.5 kV/μs o 28 kV/μs a ec s emissions be ween 10 MHz and
30 MHz.
Ou analysis shows ha he PE cable is he p ima y sou ce
o adia ed emissions, d i en by po en ial luc ua ions o he
g ound a he han ypical common mode cu en loops. The PE
cable emi s adia ed emission as a monopole an enna d i en by
po en ial luc ua ions o he EUT o he g ound. Common mode
cu en measu emen s nea he EUT, pa icula ly a 10 MHz,
p o ide be e insigh in o his adia ion mechanism han LISN
ol age measu emen s.
Con en ional EMI mi iga ion s a egies, such as choke coils
o il e s on inpu cables, a e less e ec i e o his emission
pa hway as hey bypass he inpu cables. The e o e, we p opose
he op imiza ion o swi ching ansien s and educ ion o
pa asi ic capaci ance in semiconduc o modules o
elec omagne ic emission educ ion because he high equency
componen s a e e ec i ely supp essed only by op imiza ion o
swi ching beha io and he pa asi ic capaci ance educ ion.
This s udy emphasizes he impo ance o conside ing bo h
conduc ed and adia ed emissions below 30 MHz in powe
elec onics design, pa icula ly o high-speed swi ching
applica ions.
ACKNOWLEDGMENT
EMC Ba celona con ibu ion in his pape is suppo ed in
pa by he esea ch conduc ed in he p ojec “Me ology o
eme ging elec omagne ic compa ibili y s anda ds” (21NRM06
EMC-STD). This p ojec has ecei ed unding om he
Eu opean Pa ne ship on Me ology, co- inanced by he
Eu opean Union’s Ho izon Eu ope Resea ch and Inno a ion
P og amme and by he Pa icipa ing S a es.
REFERENCES
[1] In e na ional Elec o echnical Commission, "IEC 61800-3: Adjus able
speed elec ical powe d i e sys ems – Pa 3: EMC equi emen s and
speci ic es me hods o powe d i e sys ems," IEC, 2022.
[2] CISPR 16-2-3:2023, Speci ica ion o adio dis u bance and immuni y
measu ing appa a us and me hods - Pa 2-3: Me hods o measu emen o
dis u bances and immuni y - Radia ed dis u bance measu emen s,
In e na ional Elec o echnical Commission (IEC), Gene a, Swi ze land,
2023.
[3] A. Nagel e .al, “Sys ema ic design o EMI- il e s o powe con e e s” in
2000 IEEE Indus y Applica ions Con e ence, pp. 2523 – 2525, Oc obe
2000, doi: 10.1109/IAS.2000.883177.
[4] K. Obe dieck e .al, “In luence o he ol age-dependen ou pu
capaci ance o SiC semiconduc o s on he elec omagne ic in e e ence in
Dc – Dc con e e s o elec ic ehicles”, in EMC EUROPE 2017, pp.1 -
6, Sep embe 2017, doi: 10.1109/EMCEu ope.2017.8094652.
[5] F. Cos a e .al, “G aphical Analysis o he Spec a o EMI Sou ces in
Powe Elec onics" IEEE TRANSACTIONS ON POWER
ELECTRONICS, pp.1491 – 1498, No embe 2005, doi:
10.1109/TPEL.2005.857564.
[6] J. Chen e .al, “Swi ching T ansien T aced Scheme Based on Sinusoidal
Wa e o m o Reduce EMI o IGBTs” in P oc. ECCE 2021, pp.3550 -
3554, Oc obe 2021, doi: 10.1109/ECCE47101.2021.9595912.
[7] R. Zhang e .al, “Ma hema ical Modeling o EMI Spec um En elope
Based on Swi ching T ansien Beha io ” IEEE Jou nal o Eme ging and
Selec ed Topics in Powe Elec onics, pp.2497 -2515, Ap il 2022, doi:
10.1109/JESTPE.2021.3109040.
[8] M. A. Azpú ua, M. Pous, M. Fe nandez, and F. Sil a, "Dynamic
Pe o mance E alua ion o Full Time Domain EMI Measu emen
Sys ems" in EMC EUROPE 2018, pp. 561–566, Augus 2018, doi:
10.1109/EMCEu ope.2018.8485086.
[9] J. S. Llo e as e .al, "E icien In si u Assessmen o Radia ed Emissions
using Time-Domain Measu emen s" in EMC EUROPE 2023, Sep embe
2023, doi: 10.1109/EMCEu ope57790.2023.10274192.
P oc. o he 2025 In e na ional Symposium on Elec omagne ic Compa ibili y (EMC Eu ope 2025), Pa is, F ance, Sep embe 1–5, 2025
