DESIGN CONSIDERATIONS ON THE ACTIVE FILTERFOR THE BENDING MAGNET POWER SUPPLYOF TRISTAN ACCUMULATION RING
H.Fukuma, T.Kubo, A.Kabe, S.Matsumoto,H.B aba and K.Endo
National Laboratory for High Energy Physics
The bending magnet-power supply of TRISTAN accumulation
ring is 24 pulse SCR rectifier. This power supply theoreticallyhas a fundamental ripple conponent at 1200Hz. However,due to thethree phase unbalance of the power line and the fluctuation ofthe firing angle of the SCR rectifier, lower frequency ripples
are produced. Assuming that the three phase unbalance is 3% andthat the fluctuation of the firing angle is 1°, typical voltage
ripples can be calculated and are shown in Table 1. The powers of
the ripples after passing through the passive filter are also
given. Though the higher frequency ripple conponents can be reduced considerably with the passive filter, the lower ones,especially 50 and 100 Hz, can not.
To attenuate the lower frequency ripples, the active filter
is used as shown in Fig. 1. The voltage ripple detected by theripple detecter is amplified and then applied to the primarywinding of the reactor transformer (R.T.) whose secondary winding is connected to the bending magnet bus. So as to cancel theripples on the magnet, the .output voltage has inversed phase tothe ripples. Then following relations are obtained,,
Output power of the amplifier1 )P(1H1) P ~
L~

(l+M)

2w I~,

Primary voltage across the R.T.

vp

Primary current on the R.T.

Ip= - a (l+M) I~

Cross section of the core of the R.T.
whereTotal inductance of the magnet
MSecondary inductance of the R.T.

~LuandSc= ~:f';i(jl + ilo)

1sanda = Number of the primary turns of the R.T.
Number of the secondary turns of the R.T.

~pNsis the ripple current on the R.T .. P and ware the power andtfie frequency of the ripple, respectL:ety. 9, is the average
length of the core and <'i is the gap of the core which is determined so that the iron of the core does not saturate. ~ and ~oare magnetic permeabilities in the core and vaccum, repectively.
N is limited to several turns, since the secondary winding oftHe R.T. must have the large current capacity. Therefore thebasic parameters of the active filter is determined mainly by
M and a. M is settled by optimizing the power of the amplifier
P and the cross section of the core s. Once M is determined,
a is adjusted so that Vp and I p do not exceed the maximum
I~-321-

operating range of the amplifier.
According to Table 1, total ripple power is 1.99 W. Fig. 2
shows the P's and S's as the function of M's, assuming thatN = 3, t = 1.2 m, o = 10.1 rnrn and ~ = 0.0063 H/m. From thisfigure, M is determined to 2000. If we select a to 4, follow~ng
parameters are finally obtained, N = 3, N
12, s = 0.48 m ~o = 10.1 rnrn, Ls = 525 ~H, LP = 8.4smH and P P = 3. 98 kW.
.
Reference
1) H.Baba et. al.,IEEE Trans. Nucl. Sci. NS-28,June, l981,3068

Frequency ofof the ripple
50 Hz
100
150
200
250
300

Voltageripple
2.9 X
1.5 X
5.8 X
6.8 X
5.8 X
5.8 X

Attenuation bythe passive filter

Power ofthe ripple- 6 dB-15-22-26-30-33

1.110 w
0.855
0.016
0.005
0.002
0.002

10-3
1Q-2
1Q-3
1Q-3
1Q-3
10-3

Table 1. Uncharacte ristic ripples

SCRrectifier

Passivefilter

s m.2pII transformer
Ripple

kW

1.2

10

1.0

8

0.8

6

0.6

41--..__--f detecter

0.4

s2

Load magnets ( Lt = 1.05 H)
Fig. 1. Schematic diagramof the active filter

0.2
468M

X 10-3Fig. 2. M dependence of P (the poweof the amplifier) and S(the cross section of theiron core)-322-