Clipper circuit of pulse modulator used for Klystron-5045 power supply
While the operation of modulator to the pulsed transformer of klystron-5045, current through the primary winding of the pulse transformer (PT) continues to flow even upon the end of the klystron voltage operating pulse. This is determined by an energy stored in magnetizing inductance. The prolongati...
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2001
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| Назва видання: | Вопросы атомной науки и техники |
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| Назва журналу: | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| Цитувати: | Clipper circuit of pulse modulator used for Klystron-5045 power supply / A.V. Akimov, I.V. Kazarezov // Вопросы атомной науки и техники. — 2001. — № 5. — С. 122-124. — Бібліогр.: 2 назв. — англ. |
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irk-123456789-790172015-03-25T03:02:29Z Clipper circuit of pulse modulator used for Klystron-5045 power supply Akimov, A.V. Kazarezov, I.V. While the operation of modulator to the pulsed transformer of klystron-5045, current through the primary winding of the pulse transformer (PT) continues to flow even upon the end of the klystron voltage operating pulse. This is determined by an energy stored in magnetizing inductance. The prolongation of magnetizing current passing process simultaneously with the premature choking of thyratron can cause high voltage of inverse polarity at the klystron, which cause the destruction of the cathode. We have considered the possibility of shortening time of magnetizing current passage for the charge of reasonable choice of clipper circuit parameters. The behavior of clipper circuit was studied in modulators used for the VEPP-5 (BINP, Russia) preinjector klystron power supply. The optimum operation run of the circuit was selected and its design features are described. 2001 Article Clipper circuit of pulse modulator used for Klystron-5045 power supply / A.V. Akimov, I.V. Kazarezov // Вопросы атомной науки и техники. — 2001. — № 5. — С. 122-124. — Бібліогр.: 2 назв. — англ. 1562-6016 PACS number: 29.17.+w http://dspace.nbuv.gov.ua/handle/123456789/79017 en Вопросы атомной науки и техники Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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| description |
While the operation of modulator to the pulsed transformer of klystron-5045, current through the primary winding of the pulse transformer (PT) continues to flow even upon the end of the klystron voltage operating pulse. This is determined by an energy stored in magnetizing inductance. The prolongation of magnetizing current passing process simultaneously with the premature choking of thyratron can cause high voltage of inverse polarity at the klystron, which cause the destruction of the cathode. We have considered the possibility of shortening time of magnetizing current passage for the charge of reasonable choice of clipper circuit parameters. The behavior of clipper circuit was studied in modulators used for the VEPP-5 (BINP, Russia) preinjector klystron power supply. The optimum operation run of the circuit was selected and its design features are described. |
| format |
Article |
| author |
Akimov, A.V. Kazarezov, I.V. |
| spellingShingle |
Akimov, A.V. Kazarezov, I.V. Clipper circuit of pulse modulator used for Klystron-5045 power supply Вопросы атомной науки и техники |
| author_facet |
Akimov, A.V. Kazarezov, I.V. |
| author_sort |
Akimov, A.V. |
| title |
Clipper circuit of pulse modulator used for Klystron-5045 power supply |
| title_short |
Clipper circuit of pulse modulator used for Klystron-5045 power supply |
| title_full |
Clipper circuit of pulse modulator used for Klystron-5045 power supply |
| title_fullStr |
Clipper circuit of pulse modulator used for Klystron-5045 power supply |
| title_full_unstemmed |
Clipper circuit of pulse modulator used for Klystron-5045 power supply |
| title_sort |
clipper circuit of pulse modulator used for klystron-5045 power supply |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| publishDate |
2001 |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/79017 |
| citation_txt |
Clipper circuit of pulse modulator used for Klystron-5045 power supply / A.V. Akimov, I.V. Kazarezov // Вопросы атомной науки и техники. — 2001. — № 5. — С. 122-124. — Бібліогр.: 2 назв. — англ. |
| series |
Вопросы атомной науки и техники |
| work_keys_str_mv |
AT akimovav clippercircuitofpulsemodulatorusedforklystron5045powersupply AT kazarezoviv clippercircuitofpulsemodulatorusedforklystron5045powersupply |
| first_indexed |
2025-07-06T03:07:42Z |
| last_indexed |
2025-07-06T03:07:42Z |
| _version_ |
1836865303315742720 |
| fulltext |
CLIPPER CIRCUIT OF PULSE MODULATOR USED
FOR KLYSTRON-5045 POWER SUPPLY
A.V. Akimov, I.V. Kazarezov
The Budker Institute of Nuclear Physics, 630090 Novosibirsk, Russia, Lavrentiev Ave., 11
e-mail: I.V.Kazarezov@inp.nsk.su
While the operation of modulator to the pulsed transformer of klystron-5045, current through the primary winding
of the pulse transformer (PT) continues to flow even upon the end of the klystron voltage operating pulse. This is
determined by an energy stored in magnetizing inductance. The prolongation of magnetizing current passing process
simultaneously with the premature choking of thyratron can cause high voltage of inverse polarity at the klystron,
which cause the destruction of the cathode. We have considered the possibility of shortening time of magnetizing
current passage for the charge of reasonable choice of clipper circuit parameters. The behavior of clipper circuit was
studied in modulators used for the VEPP-5 (BINP, Russia) preinjector klystron power supply. The optimum opera-
tion run of the circuit was selected and its design features are described.
PACS number: 29.17.+w
1 THE CLIPPER CIRCUIT OF THE MODU-
LATOR USED FOR THE KLYSTRON 5045
POWER SUPPLY
For the protection of the klystron and the pulse
forming network (PFN) against the energy released at
breakdown as well as for dissipation of the energy (Wµ)
stored in magnetizing inductance (Lµ) during the pulse
duration the clipper circuit switched in parallel to the
last capacitor of PFN (Fig. 1 [1,2]) is used. The clipper
circuit consists of:
- power resistor Rclip matched with the wave resis-
tance of PFN. In the case of breakdown the Rclip
should dissipate the energy stored in PFN;
- power diode Dclip designed for the total voltage
and total current of PFN discharge;
- set of varistors Var (nonlinear semi-conducting re-
sistors with symmetric characteristics I(U)).
The use of varistors is determined by the following
reasons:
- Wµ energy dissipation process proceeds faster with
varistors than without them thus the faster recovery
of the thyratron is stimulated;
- when the thyratron current is finished some nega-
tive voltage is applied at the thyratron, which also
reduces the thyratron recovery time.
In VEPP-5 modulators there are used varistors
SN-2A with classification voltage of 330 V and admis-
sible power of 2 W (the classification voltage of the
varistor is the voltage at which its current value is
1 mA) assembled in a set. A set is a parallel connection
of 48 circuits, each of which consists of two varistors
SN-2A connected in series. Thus, the total number of
varistors in a set is 96 and an admissible power dissipat-
ed in such a set is 192 W.
The set puts the limit on the value of the inverse
voltage at a klystron Ukl within the limit of 18 kV (the
transformation ratio of PT is Ktr =15). Upon reaching
this value (when the PFN capacity is recharged up to the
voltage value a few higher than the varistor classifica-
tion voltage) Iclip current begins to flow in the clipper
circuit in about 40 µs after applying the operating pulse
to the klystron (Fig. 2, curve a). At this moment, at the
nominal operation regime of modulator (klystron volt-
age Ukl=350 kV) the value of Iclip is 30 A. On the basis
of the computer simulation analysis, the maximum val-
ue of magnetizing current (Iµ) is 40 A. In this case, the
magnetizing inductance value is Lµ ≈ 3300 µH, so the
energy Wµ = Lµ× Iµ 2 /2 = 2.65 J. Assuming that all the
energy Wµ is dissipated in varistors and taking into ac-
count that the modulator operating energy is 50 Hz, we
get the mean power dissipated in varistors to be Pvar =
Wµ⋅f ≈ 130 W. This value is less than the admissible
value (actually, because of mismatching of the load and
line substantially larger energy could be released in the
clipper circuit, see below).
Fig. 1. Schematic diagram of pulse modulator used
for klystron-5045 power supply.
ВОПРОСЫ АТОМНОЙ НАУКИ И ТЕХНИКИ. 2001. №5.
Серия: Ядерно-физические исследования (39), с. 122-124.
122
0 20 40 60 80 100 120 140 160 180 200
-400
-350
-300
-250
-200
-150
-100
-50
0
50
-5
0
5
10
15
20
25
30
35
40
U
kl
, k
V
t, µ s
(a)
Iclip
Ukl
Ic
lip
, A
0 100 200 300 400 500 600
-400
-350
-300
-250
-200
-150
-100
-50
0
50
-5
0
5
10
15
20
25
30
35
40
U
kl
, k
V
t, µ s
(b)
Ukl
Iclip
Ic
lip
, A
Fig. 2. Curves of klystron voltage (Ukl) and clipper
current (Iclip) for clipper circuit with (a) and with-
out (b) varistor set.
The necessity of using varistors can be justified by
an analysis of Fig. 2 representing Iclip current curves
with (curve-a) and without (curve-b) varistors. From the
comparison of corresponding curves it is seen that the
use of varistors enables on to reduce the damping pro-
cess for Iclip down to 120 µs instead of 550 µs in case
of the clipper circuit without varistors. Reduction of this
process is caused by the necessity of providing favor-
able conditions for recovery of non-conducting state of
the thyratron. In case of a long process of current damp-
ing, thyratron cannot restore up to the beginning of the
next charge cycle of PFN that might cause short-circuit
in the charging circuit of the modulator.
In addition, with an increase in the time of dissipa-
tion Wµ (t > 100 µs) for the thyratron with lowered hy-
drogen pressure the interruption of current Iµ can occur.
The circuit is broken and energy stored in Lµ is released
in PT. Because of this circumstance the undesirable
burst of negative voltage applies at the klystron cathode.
Such an effect was found out in the process of a long
term operation of modulators at the VEPP-5 complex.
This problem can be solved in two ways: by an increase
in the hydrogen generator voltage in the thyratron and
by optimizing the selection of parameters of the varistor
set for providing the total dissipation of energy Wµ in
less than 120 µs.
2 BEHAVIOR OF THE CLIPPER CIRCUIT
AT KLYSTRON BREAKDOWN
The emergency operation run of the clipper circuit
occurred at the klystron breakdown is worth of special
mention. In such a regime the energy stored in PFN
with maximum achievable value of 800 J (depending on
the PFN-load mismatching level) will be released in the
clipper circuit. The discharge of PFN through clipper
will occur for the time equal to the pulse duration
t ~ 4 µs, therefore, the maximum power released in the
clipper circuit at the klystron breakdown can achieve
200 MW. The biggest part of the power released at the
breakdown will dissipate in Rclip. In modulators of the
VEPP-5 complex, the Rclip role is played by a set of 24
resistors TVO-60-27 (12 parallel circuits of two resis-
tors connected in series). According to reference data,
the ultimate power to be withstood by resistors TVO-60
in pulse is 25 MW. Therefore, for providing the oper-
ability of the resistor set of the clipper circuit in the
regime of breakdown it is necessary to use no less than
8 TVO-60 resistors.
3 SELECTION OF OPERATING VOLTAGE
OF VARISTOR SET
For the varistor set used at the VEPP-5 complex, the
time from the applying of operating voltage at klystron
to the moment of vanishing the inverse voltage is t ≈
150 µs. For comparison, in the clipper circuit of modu-
lators used for the klystrons 5045 power supply at the
SLAC facility (USA) a set of nonlinear resistors limit-
ing the value of Ukl_inv within the limit of 35 kV. The
use of such a varistor set enables one to get the duration
of the inverse voltage at the klystron t ≈ 120 µs which is
20% less than the duration of the inverse voltage formed
by a varistor set used in modulators of the VEPP-5 com-
plex. This is explained by the higher classification volt-
age of the set of nonlinear resistors for the SLAC ver-
sion. For reducing the applying time of Ukl_inv one has
to increase the varistor classification voltage. In this
case, the energy dissipated in the set of varistors de-
crease because of energy transmitting from magnetizing
inductance into PFN capacitance. In this case, the PFN
capacitance is recharged up to higher voltage equal to
Ukl_inv/Ktr. Then, due to the resonance discharge the
PFN charge voltage increases (in the case of absence of
the charge voltage stabilization circuit). Table 1 shows
the calculated parameters of various operation regimes
of the clipper circuit, depending on the value of the va-
ristor classification voltage and the level of mismatch-
ing of PFN and the load ρ/Rkl (ρ is the wave resistance
of PFN, Rkl is the klystron equivalent resistance).
In order to reduce the Wµ energy dissipation time, in
modulators at the VEPP-5 complex, it was suggested to
use the varistor set satisfying the following technical re-
quirements (as a result of analysis of various operation
runs of the clipper circuit the choice was made in favor
to the varistor set with the classification voltage of
ВОПРОСЫ АТОМНОЙ НАУКИ И ТЕХНИКИ. 2001. №5.
Серия: Ядерно-физические исследования (39), с. 123-124.
123
1300 V providing a rather fast dissipation of Wµ energy
at quite low inverse voltage at the klystron).
Table 1
ρ/Rkl
Varistor classification volt-
age
700 V 1300 V 1800 V
Voltage
Ukl_inv
18 kV 33 kV 45 kV
Power re-
leased in a
varistor set
in opera-
tion
regime
0.77 155 W 125 W 45 W
0.9 210 W 200 W 140 W
Power re-
leased in
resistors in
operation
regime
0.77 30 W 10 W 1.5 W
0.9 115 W 65 W 35 W
Energy
dissipated
in a varis-
tor set at a
break-
down
0.77 80 J 105 J 130 J
0.9 85 J 115 J 140 J
Energy
dissipated
in resistors
at a break-
down
0.77 500 J 475 J 450 J
0.9 580 J 550 J 525 J
Time of
inverse
voltage
applying
to the
klystron
0.77 145 µs 115 µs 95 µs
0.9 140 µs 105 µs 85 µs
Operation run (Ukl = 350 kV, Ikl = 400 A):
Magnetizing inductance current by the end of a
pulse: 40 A.
Energy stored in the magnetizing inductance: 2.65 J
(130 W).
Classification voltage of the varistor set: 1300 V.
Amplitude of short current pulses (t~2 µs): 200 A.
Power dissipated in varistors at operation with fre-
quency of 50 Hz (with taking into account mismatching
of PFN and load): 250 W.
Magnetizing current damping time: 120 µs.
Emergency regime - klystron breakdown:
Amplitude of current flowing through the clipper
circuit: 6 kA
Current pulse duration: 3.5 µs
Voltage applied to the clipper circuit: 23.5 kV
Energy dissipated in varistors: 120 J
At present, we have an agreement with VEI
(Moscow, Russia) on the production of the varistor set
with the parameters mentioned above. The use of pow-
erful varistors, which will reduce the set overall dimen-
sions and increase its reliability was mandatory re-
quired.
REFERENCES
1. I.V.Kazarezov. High-voltage semiconductor clipper
diode for pulse modulators of about hundreds
megawatt // Voprosy Aomnoy Nauki i Tekhniki,
Seriya: Yaderno-Fizicheskiye Issledovaniya
(29-30). 1997, v. 2-3, p. 173-175 (in Russian).
2. V.E.Akimov, P.A.Bak et.al. Modulators for power
supply of powerful pulsed clystrons of a cm span //
Voprosy Aomnoy Nauki i Tekhniki, Seriya:
Yaderno-Fizicheskiye Issledovaniya (31-32). 1997,
v. 4-5, p. 21-23 (in Russian).
ВОПРОСЫ АТОМНОЙ НАУКИ И ТЕХНИКИ. 2001. №5.
Серия: Ядерно-физические исследования (39), с. 124-124.
124
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