Investigation Of S High-power Pulse Modulator Based On New Types Of Saturable Pulse Transformers And A Tape-helix Blumlein Line

High power pulse modulator and technology have important applications in the fields such as defense, industry, agriculture, environmental protection, medical treatment and bioelectronics. A traditional high power pulse modulator which employs gas switch has great difficulty to enhance its repetition rate and prolong the life time; moreover, the key components of the modulator system such as the pulse transformer and high power pulse switch are independent devices which are difficult to be compactly integrated. Saturable pulse transformer(SPT) which plays as a compact integration device of the independent pulse transformer and magnetic switch can be employed to substitute the traditional spark gap switch. Through combining with the hot application requirements and promising prospects such as high repetition rate, compact integration and long life time, a repetitive high-power pulse modulator based on new types of SPTs and a helical Blumlein pulse forming line(HBPFL) is investigated in this dissertation, and the relevant key technologies and physics are also deeply revealed. The main contents and innovative points are as follows.1. Investigation of the dispersion theory and dispersive characteristics of HBPFLA set of theoretical tape-helix dispersion model and method of helical pulse forming line/transmission line is set up to investigate the helical dispersive characteristics and relavant physics under all kinds of complicated conditions.(1) The helical dispersion shows strong effects on the high-frequency transmission line and ns-range short pulse forming line; in the low-frequency band which corresponds to a 100ns-range pulse forming course, the basic spatial harmonic component(0th) of the electromagnetic wave determines the dispersive characteristics of the total HBPFL; as the electromagnetic coupling between the inner line and outer line of the HBPFL is considered in the proposed tape-helix dispersion theory, the relative error of parametric calculation from the theory is less than 5%.(2) A two-layer helical tape current model is put forward, and the established dispersion theory based on this new model can analyze the effects of tape width and radial dielectric discontinuity on the characteristics of the HBPFL, which also provides an important method for the analysis of the multiple layers of coupled helical coils.(3) Through transforming the multiple-filar “narrow-tape” model into the unifilar “wide-tape” dispersion model, the dispersion characteristics of the multiple-filar type HBPFL are investigated by the proposed dispersion theory; as the multiple-filar tape helices have more uniform distributions of helical tape currents and surface electric field intensity, they guarantee superior dispersion and insulation characteristics.(4) A set of dispersive propagation theory and method of traveling electromagnetic waves is put forward for the HBPFL with a finite length and dielectric discontinuity in the axial direction; the effects of dispersion and axial dielectric discontinuity on the wave transmission and reflection at the ports of HBPFL are studied in detail.2. Investigation of the important scientific problems, physics and key technologies of the new types of SPT(1) The inter-lamina inductive voltage of the ribbon-wound magnetic core of SPT is analyzed, and the insulation characteristics and physics of the insulated coatings(thickness of 1.5 μm) of nanocrystalline ribbon under repetitive ns-range voltage pulses are also revealed, in order to provide important instructions for magnetic core design under high-voltage pulses. A model of heat ablating accumulation(caused by high-temperature plasma bombardments on the coating) and coating smashing effect accumulation(caused by the plasma channel expansion stress) is put forward to explain two physical problems: one, repetitive ns-range voltage pulses show much stronger destructive effects on the coating than a single pulse does; the other, transformer oil allows a much higher breakdown voltage of the immersed ribbon coating than air does.(2) Three new types of SPT are put forward and produced, such as the type of multiple subgroups of windings in parallel combinations, the mutual-coupling type of coaxial cylindrical windings, and the self-coupling type of fully coaxial windings. These SPTs have advantage of high repetition rate and great potential of long life time. The saturated inductance of the secondary windings of a common SPT can be reduced by one order of magnitude, after the new structures are employed. It means that the hard problem of the common SPT which can not obtain high step-up ratio and low saturated inductances of windings simultaneously is preliminarily solved. The new SPT which achieves a compact integration of independent transformer and magnetic switch can substitute the traditional gas switch to play both as the step-up transformer and main switch for the high-voltage capacitor or pulse forming line.(3) A kind of theoretical model, which describes the leakage magnetic field distribution and the saturated diverging magnetic fields coupling of the sparse helical coils with a finite length and a rectangular cross section, is put forward to calculate and analyze the characteristic parameters of the SPT.(4) According to the proposed magnetic theory, a crucial physical mechanism is put forward and demonstrated as follows: the reversed magnetic coupling effects of the saturated diverging magnetic fields among multiple windings can be employed to maintain the saturation of core and suppress the saturation inductance of the SPT windings to a level lower than their intrinsic structural inductance.(5) A set of analytical circuit method is established to analyze the complicated coupling work courses, key mechanisms and work order of the two stages of SPT modulation units in series.3. Investigation of the new SPT applied in compactly integrated Marx generator and synchronization of ns-range multiple voltage pulses(1) A new 100 k V-range Marx generator with gas switches substituted by the new SPT is initially put forward and investigated. A 3-stage Marx generator of this type which achieves a highly compact integration of pulse transformer, magnetic switches and common Marx generator can obtain the step-up times more than 100. In view of that the new Marx generator sharply decreases the input charging voltage(<1 k V), it provides a new way for Marx generator with high repetition rate and long life time.(2) A new synchronization technology for high-voltage ns-range multiple pulses based on the new SPT is put forward and demonstrated, and the proved synchronization accuracy is of ns range.4. Investigation of a high power pulse modulator based on the proposed SPTs and a HBPFLA new technological scheme of high power pulse modulator based on an HBPFL driven by two stages of SPT units in series is put forward and demonstrated, and a 200 k V pulse modulator is produced, in which the produced new SPTs play both as the step-up transformers and magnetic switchs. The produced pulse modulator has advantages of high repetition rate, compact integration and the potential of long life time. The magnetic cores are auto-reset in the two stages of SPT modulation units. Firstly, in the once charge and single shot mode, the modulator can deliver a unipolar single voltage pulse on a 160 ? load, with pulse amplitude, full width at half maximum(FWHM) and pulse rise time of 180 k V, 135 ns and 60 ns, respectively. Secondly, in the once charge and burst high-repetition mode, the modulator can deliver two or three 100 k V-range bipolar voltage pulses on the 160 ? load, and the burst repetition rate is higher than 33 kpps(thousand pulse per second).