The paper presents an analytical discussion of the amplitude of a transient process in a simple oscillatory network that includes a non-linear capacitor. Analysis of the transient process became worth white recently because of the appearance of proposals in the technical literature to use non-linear capacitors in electronic starters in fluorescence lamp fixtures, in which transient spikes play a role as ignition pulses, where the increase in the amplitude is important. It is shown to be profitable to study some voltage-voltage functions related to the transient process, to determine parameters of the voltage-charge characteristics of the capacitors. Optimization of the form of the capacitor's characteristics leads directly to the use of a voltage-controlled switched capacitive subcircuit, which can be replaced by a switched non-pure-capacitive circuit. The analysis may be relevant for the specification and standardization of capacitors intended to be used as non-linear elements in special pulse g...

The use of non-linear capacitors

A nonlinear capacitive turn-off snubber is discussed. Customarily, only linear capacitors are used in high-frequency power electronic switches. However, ceramic ferro-electric materials, with ratios of initial to final capacitance of nearly 30, are found suitable and are investigated. The energy stored in these nonlinear capacitors, with an initial capacitance of 300 nF, amounts to only about 1.1 mJ at 300 V compared to 13.5 mJ in a 300-nF linear capacitor. As far as the power switch is concerned, the difference in switching behavior and switch turnoff loss between these two cases is negligible. This nonlinear snubber is analyzed approximately by assuming an exponential relation between capacitance and voltage, as well as with a more accurate analysis by means of a computer program. The latter uses an exact capacitance-voltage curve stored on a data file. Computed values correlated well with experimental measurements. As the dielectric losses in the ceramic material are very important, careful calorimetric measurements in situ revealed an energy loss in the capacitor of 135 ?J per turn-off cycle, taken at 500 Hz, 30 A, and 300 V.

Study and Application of Nonlinear Turn-Off Snubber for Power Electronic Switches

Study and application of nonlinear turn-off snubber for power electronic switches

The optimization of the general turn-off snubber, consisting of a nonlinear saturable snubber capacitor with an energy recovery circuit, is done in terms of minimum total energy loss in the power electronic turn-off circuit. To analyze this nonlinear circuit without a computer simulation, a two-step piecewise-linear approximation of the capacitor's capacitance-voltage curve is presented. Results regarding the total energy loss in the circuit during the switch turn-off indicate that the nonlinear capacitor as a snubber element is superior to the normal linear capacitor even if the ceramic capacitor is used only up to its specified voltage value. >

Optimum nonlinear turn-off snubbers: design and application

Ferroelectric capacitors whose rated voltage is basically defined by the requirement of a fair linearity of the (generally nonlinear) capacitors’ voltage–charge characteristic, not by the breakdown voltage, which can be much higher, are widely used today. It is noted, and considered with some details, that the use of such a capacitor in a simple switched-capacitive circuit which imitates a resistance enables a nonlinear frequency-controllable resistance to be obtained, and that the use of such a capacitor as a load for a gyrator circuit enables a nonlinear inductor to be obtained. The topic is interesting from the basic circuit theory aspect, in view of the fact that ferroelectric ceramic capacitors are widely used today, and because of the need to find ways for integral implementation of different nonlinear elements.

A nonlinear resistor and nonlinear inductor using a nonlinear capacitor

Failure in ceramic capacitors due to high-impulse voltages was investigated to determine the parameters which limit the breakdown voltage. It was found that the breakdown field strength is a function of the dielectric constant, the dielectric thickness, and the capacitor area. There was little correlation between the breakdown voltage and the rated voltage. Breakdown usually occurred at the edge of the electrodes, and only small changes in capacitance and dissipation factor resulted.

Breakdown in Ceramic Capacitors Under Pulsed High-Voltage Stress

Capacitors subjected to short, constant current pulses will fail when the voltage reaches the breakdown value. A summary of experimental results on breakdown in glass, mica, plastic film, ceramic disc, ceramic multilayer, aluminum electrolytic, and tantalum capacitors is presented. The relationship between breakdown voltage and dielectric material, dielectric thickness, voltage rating, capacitance value, and capacitor construction is discussed.

H. Domingos

Papers

Breakdown in Ceramic Capacitors Under Pulsed High-Voltage Stress

Breakdown Voltage of Discrete Capacitors Under Single-Pulse Conditions