Classifications

• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03K—PULSE TECHNIQUE
  • H03K3/00—Circuits for generating electric pulses; Monostable, bistable or multistable circuits
  • H03K3/02—Generators characterised by the type of circuit or by the means used for producing pulses
  • H03K3/53—Generators characterised by the type of circuit or by the means used for producing pulses by the use of an energy-accumulating element discharged through the load by a switching device controlled by an external signal and not incorporating positive feedback
  • H03K3/537—Generators characterised by the type of circuit or by the means used for producing pulses by the use of an energy-accumulating element discharged through the load by a switching device controlled by an external signal and not incorporating positive feedback the switching device being a spark gap

Definitions

• the present invention relates to a very high voltage and high current pulse generator.
• the required pulses are rectangular pulses, of very high voltage (greater than 500kV), delivered at an impedance of 500 to 3000 Ohms, with the shortest possible rise time. and an amplitude plateau as flat as possible, with a duration of 100 nanoseconds to a few micro-seconds.
• a low-impedance training line consisting of discrete components (capacitances and inductances) is generally used.
• a high voltage thyratron controls the discharge of the line. Since the operating voltage of the thyratrons does not exceed 60kV, we are led to use a step-up transformer. Due to the necessary electrical isolation, linked to high voltage, this transformer must have significant magnetic leaks, limiting the rise times of the output pulse. Practically, at 500kV, the rise time will be close to one microsecond. This rise time can only increase with the output voltage.
• FR-A-2 638 304 high voltage pulse generators comprising coaxial cables charged in parallel by a high voltage source and discharged in series through switches. If T is the transit time in a cable and V the charging voltage, we obtain with n cables a voltage of amplitude nV / 2 and duration 2T.
• the object of the present invention is precisely to remedy these drawbacks by proposing a generator capable of working at very high voltage (several hundred kiloVolts), at high current, therefore at very high power. To this end.
• the generator of the invention provides for the use of spark gaps and load and trip resistors which do not see very high voltage.
• the subject of the invention is an electrical pulse generator of the kind of that of document FR-A-2 638 304, and which is characterized laughed at by the fact that:
• the switches are spark gaps having a first electrode connected to the inner conductor of a cable and a second electrode connected to the outer conductor of the next cable and a trigger electrode connected to the trigger control circuit, two balancing resistors being provided between the first electrode and the tripping electrode and the second electrode and the tripping electrode, - load resistors are provided between the outer conductors of the coaxial cables and between the inner conductors of said coaxial cables.
• FIG. 1 is a diagram of an embodiment of a generator according to the invention.
• FIG. 2 shows an example of pulses obtained by the generator of the invention.
• FIG. 1 shows a generator comprising three commercial coaxial cables C1, C2, C3, each with an outer conductor Ce and an inner conductor Ci, three spark gaps E1, E2, E3, a high voltage source SHT and a CD trigger circuit.
• the SHT source is connected to the cables p ⁇ of the load resistors R1, R2, R3, R4, R5, R6.
• the resistors R4, R5 and R6 are arranged between the outer conductors of the cables and the resistors R2, R3 between the inner conductors.
• the trigger circuit CD is connected to the spark gap trigger electrodes through a capacitor C and trigger resistors -M, r2, r3. Additional resistors r, r 'balance the voltages between the main spark gap electrodes and the trigger electrode.
• the main electrodes of the spark gaps are connected, one to the inner conductor Ci of a cable and the other to the outer conductor Ce of the following cable.
• the generator has a general output S connected to the external conductor of the last cable.
• the operation of this device is as follows.
• the three cables are first charged in parallel by the high voltage source SHT.
• the control of the three spark gaps has the effect of connecting the three cables in series, which will discharge and cause a voltage pulse to appear on the general output S.
• a line charged at a voltage U when discharged on a charge equal to its characteristic impedance Z, delivers a pulse of amplitude U / 2 and of duration equal to twice the propagation time in this line.
• T this propagation time and if N is the number of cables, we obtain by the generator of the invention, a pulse of duration 2T, of amplitude NU / 2 on a load of impedance NZ, (N is equal to 3 in the illustrated variant).
• N 3 in the illustrated variant.
• N 20
• the high voltage power supply SHT can be a commercial supply of 130kV, 5mA.
• the trigger circuit can generate pulses of very short duration, about 10ns. All of the elements can be immersed in an oil tank, which guarantees electrical resistance at the desired maximum voltage.
• each cable is wound with, its resistors and its spark gap.
• Each floor thus has a modular character.
• the operating frequency is limited by heating due to ohmic losses in cables, in spark gaps, dielectric losses in cables and oil, convection movements induced in oil by the applied voltages. ⁇ quies and by The power of the power supply continues.
• the production of ionizing radiation, if the charge is an electronic gun, can also limit the rate of operation in the event that protections are not provided.
• Figure 2 shows a pulse obtained by the generator of Figure 1.
• the duration is close to 1 microsecond and the amplitude is of the order of 150kV.

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• 1990
  • 1990-08-28 FR FR9010718A patent/FR2666462A1/fr active Pending
• 1991
  • 1991-08-27 US US07/847,986 patent/US5399910A/en not_active Expired - Fee Related
  • 1991-08-27 JP JP3515485A patent/JPH05502361A/ja active Pending
  • 1991-08-27 EP EP91916403A patent/EP0497965A1/de not_active Ceased
  • 1991-08-27 WO PCT/FR1991/000691 patent/WO1992003875A1/fr not_active Ceased

Non-Patent Citations (1)

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