Abstract
A review of studies of processes that occur in the dielectric of cosine self-healing metal film capacitors under the influence of exceeding the permissible heating temperature and overvoltage is presented. The relationship between operating conditions and service life of capacitors is considered. Methods for determining the self-heating temperature of capacitors under the influence of higher harmonic components of current and voltage are considered. The correct interpretation of cosine self-healing metal-film capacitors parameters specified by manufacturers in technical documentation is presented in relation to the concept of nominal service life. It is proposed to use the parameters coefficient of harmonic overload of the capacitor, coefficient of change in service life and coefficient of use for reactive power-to analyze the operating modes of capacitors. The calculation of the operating parameters of cosine self-healing metal-film capacitors with a nominal voltage of 400÷525V, belonging to different temperature classes, at different air temperatures in the room of the electrical installation and connected to the electrical network with a voltage of 400V with different levels of higher harmonic voltage components. Variants of operation of capacitors as part of reactive power compensation devices, including using anti-resonant chokes, were considered. The values of capacitors self-heating temperature are determined, taking into account the influence of higher harmonic leaving factors. The values of the service life change coefficient, the harmonic overload coefficient of the capacitor, and the reactive power utilization coefficient are determined. The dependences of reducing the service life of the capacitor coefficient on the values of the total coefficient of harmonic distortion in voltage are obtained. The results of calculating the operating parameters of cosine self-healing metal film capacitors are analyzed. It is established that the use of cosine SMCS belonging to temperature classes A and B in devices for compensation of inactive power is not technically acceptable for the consumer and is not economically feasible. The use of cosine SMCS belonging to the temperature class D and higher is preferred. The voltage rating of the capacitor should be determined based on the level of higher harmonic voltage components, rated voltage and positive bias voltage in the electric network. The following parameters are confirmed as the criteria for selecting the nominal voltage of the capacitor: the coefficient of harmonic overload of the capacitor, the coefficient of reducing the service life and the coefficient of use for reactive power.
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