Peak Inverse Voltage Research Articles

An Electronic Switch for the Transient Testing of AC Networks and Machines

The paper describes an electronic switching device for the transient testing of small ac machines and network models. It is suitable for single-phase or three-phase operation. Precisely timed switching transients can be produced in any or all phases of the tested system. Switching operations in the individual phases can be performed simultaneously or with independent timing. The accuracy of timing is ± 0.5 electrical degree with a timing range from 0 to 2777 cycles. Thyristors are used as the main switching elements. They can continually carry 265 A r.m.s.; the peak inverse voltage across the switching elements is 600V. Several tests, which have been carried out with the device so far, are described and typical test results are given.

Equipment and materials

The Ministic high voltage subminiature multi‐purpose silicon rectifiers are cylindrical with an insulated case and silver leads. The peak inverse voltage is 8000 to 14,000V; maximum static forward voltage at 10MA is 20V; the average rectified current at 25°C is 10 milliamps and the maximum static reverse current, at PIV is 0?5UA at 25° and 20UA at 100°C.

Nonlinear Analysis of the Schottky-Barrier Mixer Diode

The waveshape of the local-oscillator voltage component that exists across the nonlinear junction of a Shottky-barrier diode is a fundamental determinant of mixer performance. This waveshape significantly differs from that of the total local-oscillator voltage impressed across the diode terminals since it is influenced by parasitic, particularly spreading resistance and contact inductance, which exist in series with the junction. The junction-voltage waveshapes resulting from a 9.375-GHz sinusoidal local-oscillator generator voltage are computed for three common equivalent-circuit models of the diode. In the first model the diode is represented by a nonlinear conductance in series with a fixed spreading resistance. The second model includes the nonlinear capacitance associated with the junction, and the third additionally includes the contact inductance. In each case, the junction-voltage waveshape is significantly nonsinusoidal. It is shown that the contact inductance can induce a peak inverse junction voltage that greatly exceeds the peak voltage impressed across the diode terminals. This parasitic reactance thus can have an important bearing on the burnout properties of the mixer diode.

Silicon rectifier chains for accelerating voltage supplies†

Abstract Silicon rectifiers when cascaded in series to provide a high peak inverse voltage rating, depletion capacitance and saturation current, create some problems regarding over-voltage protection of the rectifiers. In this paper these problems are discussed and possible solutions suggested for systems operating at high supply frequencies. Expressions and curves are given for the design of protected rectifier chains suitable for the high voltage supply of particle accelerators.

A Three‐Point Probe Method for Electrical Characterization of Epitaxial Films

A three‐point probe has been devised which makes possible simple, rapid measurements of resistivity and conductivity type of epitaxial silicon films. The probe in contact with a silicon crystal is effectively a point‐contact diode with ohmic base termination. The external circuitry measures this “diode's” V–I characteristics. Its peak inverse voltage is a predictable function of resistivity and hence resistivity is determined from this parameter. The advantage of the probe is that special preparation of rectifying and nonrectifying contacts is not necessary. The design, calibration, and operation of the probe are discussed in addition to some experimental results such as resistivity as a function of location within the reactor and a relatively simple method for measurement of resistivity gradient in the film. Finally, the method's limitations in measuring thin, high resistivity films are described and capability limits defined.

Growth of α ‐ SiC Single Crystals from Chromium Solution

The travelling solvent method of crystal growth has been successfully adapted to the growth of single crystals, using pure chromium as the solvent. Since molten chromium does not wet chemically cleaned in a uniform and reproducible manner, a prewetting procedure was developed which involves a heat treatment of the at 1200°–1300°C in vacua at 10−9–10−10 Torr, followed immediately by the evaporation of a thin (104Aå) film of pure chromium onto the clean surfaces. The chromium solvent zones were passed under the influence of a temperature gradient in a simple r. f. furnace; the average specimen temperature was 1750°C. Subsequent metallographic and x‐ray examination revealed that good crystal growth had occurred. Growth rates of the order of 0.75 mm hr−1 were obtained under the above conditions, p‐n junctions prepared by deposition, from chromium solution, of one conductivity type onto the opposite type were assembled into diode structures. Junction capacitance varies with bias in accordance with a law, indicating an abrupt (step) junction. The forward I–V characteristics are unique for SiC devices in that the forward voltage drop is 1.2–1.5v compared to 2–5v reported for previous diodes at comparable current densities. The slope of the forward biased characteristics was found to be e/2.4kT. Considerable leakage is observed (under reverse bias); the peak inverse voltage, which ranges from 6–15v, is much lower than expected from the resistivity of the bulk material. This low voltage breakdown is tentatively discussed in terms of a peculiar dislocation structure in the region of the p‐n junction. The over‐all rectifying properties of the devices prepared by TSM persist up to at least 540°C.

The relation of arc-back to ion density and inverse field in arc-discharge rectifiers

Arc-back is believed to occur at the end of forward conduction as a result of acceleration of positive ions to the anode in the inverse field. The frequency of arc-back increases with the rate of fall of forward current and with the peak value and rate of rise of the inverse voltage. The ion density is proportional to the rate of fall of current, but with a constant that depends on the waveform of the current fall and on the lifetime of the ion in the arc; and the latter varies with the load. Observations of individual arc-backs show that the time of occurrence and also the ion density and inverse voltage at the time of arc-back vary widely. At low rates of fall of current arc-back occurs most often at the time of peak inverse voltage, not of peak reverse current; but the occurrence is more random at high rates of fall of current.

Preparation of Large-Area p-n Junctions in Silicon by Surface Melting

Two methods have been developed for the preparation of large-area p-n junctions in monocrystalline silicon by surface melting and overdoping of the molten material. In one method, direct rf power coupling is used to form a cylindrical p-n junction in a rod of silicon. Also, radiation heating has been used to melt the surface of thin disks of silicon. The junctions can sustain a peak inverse voltage (PIV) given approximately by PIV=40ρn or PIV=10ρp depending on the polarity of the base material, of resistivity ρn or ρp. Low-resistivity n-type base material overdoped with aluminium forms junctions exhibiting very sharp breakdown characteristics, and PIV=40ρn holds for material at least up to 15 ohm cm. Some results obtained by using a gas doping technique are also given.

A High-Voltage, Cold-Cathode Rectifier

A new cold-cathode, high-voltage rectifier is described. Both theory and extensive experimental data are included. The operation of the tube is based upon an improved type of electron trapping similar to that occurring in a cylindrical magnetron in the cutoff condition, but augmented because of the use of end plates on the cathode. Mercury vapor is used, which at normal operating temperatures, provides a gas at a pressure of from 10-3 to 10-2 mm of Hg. Because of this low pressure and the small dimensions of the tube, ionization is inhibited when the cathode is positive, and highpeak inverse voltages are possible. However, when the anode is positive, the improved electron trapping results in conduction in spite of the low pressure and small dimensions. Experimentally, this rectifier has been operated up to 40-kv peak inverse voltage. Life tests at 30-kv peak inverse voltage and a current of 0.4 ma, at 60 cps, have run to 3,000 hours. Satisfactory operation has been obtained over a temperature range from 20 to 80 degrees C. The upper frequency limit lies between 120 and 240 kcps. This tube appears to offer, for the first time, a practical cold-cathode rectifier for output voltages up to 14 kv and currents up to one ma. Its advantages are particularly valuable in the case of voltage-multiplier rectifier circuits, since high-voltage insulated cathode-heater transformer windings are not necessary.

A 500-Kilovolt Linear Accelerator Using Selenium Rectifiers

A 500-kilovolt generator for use on a linear accelerator is described. This voltage is obtained by using selenium rectifiers and one microfarad condensers in 22 stages of voltage doublers. The maximum input is nine kilovolts r.m.s. at 750 cycles, and the maximum peak inverse voltage across each rectifier and each condenser is 25 kilovolts. The measured regulation is 25 kv/ma, the measured ripple (peak to peak voltage) is less than 1200 volts/ma; both independent of output voltage. The maximum load is 2.5 ma.

Hot-Cathode Mercury-Vapor Rectifier Tubes

High-voltage d-c power for radio transmitters has usually been obtained from d-c generators or through rectification of alternating current by means of high-vacuum tube rectifiers or mercury-arc rectifiers. A new type of rectifier tube is described which combines the advantages of the high-vacuum tube with the low and nearly constant arc-drop of the mercury-arc rectifier. Typical tube characteristics and the method of operation are discussed. A method is given for rating rectifier tubes in terms of the fundamental limits of the tube, that is, peak inverse voltage and peak plate current. Single-phase and three-phase circuits are shown for use with the hot-cathode mercury-vapor tube.