The 11th Symposium on Accelerator Science and Technology, Harima Science Garden City, 1997

Effect of Common Mode Static Filter·in High-Perfo rmance Synchrotro n Power SupplyHiroki TAURA, Jumei MATSUI*, Kichiji HATANAKA, Yutaka TAKAHASHI,
Akiyoshi TERAMOTO* , Isao UCHIKI*, Katsuhisa SAKO*, Kenji SATO
Research Center for Nuclear Physics, Osaka University,
10-1 Mihogaoka, Ibaraki, Osaka 567, Japan*Energy and Industrial Systems Center, Mitsubishi Electric Corporation, Kobe 652, Japan
Abstract

2 Measuremen t Results

The power supply for synchrotron magnets was produced to test its performance. It has a common mode
static filter of reactor type, and this filter can be bypassed. In this paper, an equivalent circuit model of thepower supply can explain those measurement results.

The output voltage between positive· and negativelines, that is to say, a normal mode output voltage wasmeasured by using FFT analyzer at a current of 1500A
without pattern operation. Output ripple voltage without common mode reactor is shown in Fig 2, with itin Fig 3, respectively. When common mode filter wasequipped, 4J.tF capacitor was inserted between the magnet coil and the ground line to emphasize the common
mod~~v~:~ ._ .
. ~-.. ~---- ____ ==~~
1

1 Specifications , Features, and Environment s ofTest
Specifications are listed in Table 1, environments ofperformance test in Table 2, respectively.

1800117.(5")
LoDM8g~~Table 1
Specifications of power supply
RectifierMaximum Current
Maximum Voltage

468011z(IJ")-----1--/d!Y2520IIz(7")

I.

-j -H

6840IIz(l9")_7560IIz(21"J

12-Pulse Thynstor Rectifier
3000A, DC
210V
Start:!.BkH:r.

Stott:

B. 2

kH:r.

Fig. 2 Output ripple voltage without common mode
reactorTable 2
Environments of performance test
LOadInductance
Resffitance~12011z(l7')

5400IIz(IS")-----1TRISTAN 2 quadrupoles
24mH
26mn

LoaMeg10

1-f-----f----f---l--f---l---H

dB

1-1----T-- -1---f--1-- +:--H/d!v

This power supply has the following features;a) All elements are disposed symmetrically up anddown to the ground line.(see Fig 1)b) It has two kinds of static filters around the groundline. One is of normal mode reactor type and theother is of common mode one. The common mode
filter can he bypassed to measure the frequency
characteristics without it.

Stott:B. 2kHZ

Fig. 3 Output ripple voltage with common mode reactor
These mean the following;(A) Common mode filter cannot reduce the amplitudeof the ripple of720n [Hz] (n is integer).

(B) Though normal mode output voltage was measured,common mode filter can reduce the amplitude of the360(2n- 1) [Hz] components.
+.

i.1______________________ ~+.--~____J

Fig. 1 Single line diagram of the power supply(C) With the common mode reactor, for 360(2n-1) [Hz]components, the higher the frequency is, the larger
the attenuation ratio of ripple voltage becomes.
To explain these phenomena, we assume the following equivalent circuit model of a power supply.

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The 11th Symposium on Accelerator Science and Technology, Harima Science Garden City, 1997

3 The Model of Power Supply

Jo- JpC,U

The stray capacitances exist between the midpointof each thyristor bank and the ground line. It is provedthat the commutation spike appears only when outerthyristors are turned on, since there are difference between outer thyristor bank and inner one. [1]But our measurement results are explained if thyristor banks up and down to the ground line are slightly
different. Thus, for simplicity, we will analyze the circuit model which have asymmetrical input part to theground line and symmetrical two filters and loads.
Here, Cu stands for the capacitance of the thyristor
bank disposed up to the ground line, C1 down to theground line and cl is the capacitance of the midpointof the both thyristor banks, respectively. The leakage
inductances of transformer is Lu and L 1, voltage of upper and lower thyristor banks are v and u, respectively.
These capacitances and inductances are slightly different from each other. And static filters and magnets aredisposed symmetrically to the ground line. (see Fig 4)

l+J
1-J

Yc (V- U)

The solutions of these equations are as follows;

acommon mode fllt11r

normal mode niter= M(v+u)+N(v-u ),

( 1)
(2)

=2(2Cl + Cu + C,) p+2 (Cu C, (Lu + L1) + 2Cl (Cu Lu + C1 L1)) p3+4Cl Cu C1 Lu L1 p5+ (4 + (2Cl + Cu + Cl) (Lu + L,) p2+ ((2Cl + Cu + C,) (Lu + Li) p 2+2Cl Lu L1 (Cu + C,)p4 ) Yn+ (2(Lu + L1) + 4Cl Lu L1 p 2 ) p Yn Yc(3)

A2(Cl + Cu + C1) p + 2Cl (Cu Lu + C1 L,)p3+2(2+Ct(Lu+LI )P2 )Yc(4)

B

2Cl p 2 ((C1 L1- Cu Lu) p + (L1- Lu) Yc)
2(Ct- Cu) p + 2Cl (Ct Lt- Cu Lu) p3+2C!{Lt- Lu) p2 Yn
4C1P+ 2Cl (Cu Lu + Ct Lt)P3+2Cl{Lt + Lu)p2 Yn.

Nmq:netsA ( v + u) + B (v - u)a(V-U)+2C1LuLI(Cu +Ci)p4 ) Yc

M

I"Pttt IM'ta ( V + if)

whereR(ll!rY''"""tryYn (V + U)

port)

(5)
(6)
(7)

I

Fig. 4 The ail-in-one diagram of the model of power
supply and equivalent circuit of magnets

3.1 The Normal and Common Mode Admittances ofSymmetric Part
When elements are disposed symmetrically to theground line, normal and common mode are decoupled. [2],[1] Yn and Yc express the normal and common
mode admittances of symmetric part that consist of thetwo static filters and magnets. So,

I+ J
1-J

=Yn (V + U)

= Yc(V-U),

where Yn and Yc are the function of Laplace differential
parameter p. (In our power supply, the resonant frequency of normal and common mode reactor are 10kHz,8kHz, respectively. [3])3.2 Input Part (Asymmetric Part)By applying the Kirchhoff's law the following set ofequations are obtained. (see Fig 5)

vuJFig. 5 Block diagram of input part3.3 Input Voltage
For simplicity, controlled angle a = 0 is assumed.
In the case of 12-pulse rectification, the basic ripple frequency of power supply is 12 x f 0 [Hz] for normal modeand 6 x f 0 [Hz] for common mode(/0 = 60 Hz). (SeeFig 6, where the maximum amplitude of normal mode
input voltage is set equal to 1 Volt.)
So, (v+u)(t) and (v- u)(t) are expressed as follows.
00(v + u)(t)W+v-pLulo-W+u-pL,JoJo- Io

pC1 W

Io- I

pCu V

=L Vn exp(27ri ·12nfot)
n=O00(v-u)(t)I: v~ exp(27ri . 6nfo t)
n=O-393-The II th Symposium on Accelerator Science and Technology, Harima Science Garden City, 1997

Fourier transforms of them are as follows.

is higher, IAIA'I becomes smaller. And from(3),(4), for Cu ~ Ct
C, Lu ~ L1
L,
lal ~ I1+CLp2 +pLYniiAI· Since I1+CLp2 +pLYn I is invariant with common mode filter,lala'l ~ IAIA'I· Thus lala'l also becomes
smaller, G~~r:_irJ.al becomes smaller in high frequency region.

=00

2:::: Kn 8(!- 12nfo)(v+u)(f)

(8)

n=O
00

L K~ 8(!- 6nfo)(v-u)(f)(9)n=D=(b) For the 720n[Hz] ripple, from (8),(9), both thefirst and second term of the right side of ( 1)relate to G. But since slight are the differences
between Cu and C1 or Lu and L,, IBI ~ IAI,
IB'I ~ IA'I· So"'- Normal mode input voltage

cnormal _ lA' Ia' I
2n- IAial
Because of lala'l ~ IAIA'I, G~~rmal ~ 1.
As mentioned above, we can explain the measurement results (A), (B), (C).

21r fo tFig. 6 input voltage

2. Common mode output
IM'I = IMI and IN'I = INJ, for the 360nHz ripple.
Thus

3.4 Attenuation Ratio with Common Mode Reactor
The values of Yc, a, A, B change with common mode
filter.
Those parameters with it are expressed as
Y;, a', A', B', respectively. G is defined as attenuation
ratio of amplitude of ripple voltage with it at output ofthe power supply. From (1),(2),(8),(9), G is formulated
as follows.

IV+ Ulwith com. filter
IV+ Ulwithout com. filter

cnormalIf Cu "# Cr,Lu "# L1 are assumed, the present measurement data is explained. Common mode filter is effective in improving the performance of power supply, asshown in the measurement data. We propose that common mode filter should be equipped with every power
supply.
By this analysis, we show that common mode reactor
is effective even if C 1 is a finite value. But since there
is no data when cl is finite, output voltage should bemeasured when cl is finite and infinite. If cl is allowed
to be a finite value, disposition of power supply become
simple.

la'l2 IAI2Jv + ul2 + IBJ2Jv- uj2

IV- Ulwith com. filter
IV- UJwithout com. filter=But there is no measurement data of common mode
output voltage.
4 Discussion

El:_ IA'I21v + uj2 + IB'I21v- ul2
ccommonccommon = lala'l ~ 1.

Jal 2 IM'I 2 lv + ul 2 + IN'I 2 Iv- ul 2la'l 2 IMI 2 Iv + ul 2 + INI 2 lv- ul 2
1. Normal mode output(a) For the 360(2n- l)[Hz] ripple,

Acknowledgement

G~~':_~al = IB' I Bllala'l·Here, IYcl ~ JY;I, difference between Lu andL 1 is slight and IPI,...., (10 3 "' 10 4 ), so jB' I Bl ~1. Thus~~~a!~ iala'i ~ 1.
Moreover, if we assume Cu ~ C1 = C, Lu ~Lt = L, jAj ~ j4Cp(2+CLp 2 )+4(1+CLp2 )Ycl,thenCp(2 CLp(1 CLp2)Yc I
IA'A I ICp(2CLp2)
CLp2)Yc' .
=++2) +++ (1 +The authors would like to thank Dr. M. Kumada forkind advice.
References[1] K. Sato, private communication.
[2] M. Kumada, "ANALYSIS OF RIPPLE CURRENTAND ITS PERFORMANCE IN HIMAC SYNCHROTRON POWER SUPPLY" ,1996.
[3] J. Matsui et al, "Performance of the test power supply for synchrotron magnets,l996.

Typically, C ,...., 10- 9 F, L ,...., 10- 2 H. Thus,
when 1(1 + CLp 2 )Y;I increases as frequency-394-