Testing method for detecting internal ESL of self-healing type metallized film capacitor

Abstract

The invention discloses a testing method for detecting internal ESL of a self-healing type metallized film capacitor. A special short-circuit discharging testing loop is formed by a switching cabinet,a voltage adjusting device,a transformer,a silicon stack,a protecting resistor,a high-voltage switch,a discharging device,a heavy current discharging switch,a current transformer,an oscilloscope,a connecting guiding wire,a tested sample,an accompany sample and the like,and corresponding waveforms are obtained; according to principles of electric and electronic engineering,computing of the ESL of the loop is conducted according to the waveforms,final sample ESL is obtained through a difference method,and the blank of a precise measuring and testing method of ESL of capacitors in current industries is filled.

Description

technical field [0001] The invention relates to the technical field of metallized film capacitors such as DC support capacitors, locomotive capacitors, and pulse capacitors, in particular to a test method for detecting the internal ESL of a self-healing metallized film capacitor. Background technique [0002] Self-healing metallized film capacitors are widely used in flexible DC transmission, railway transportation, special impact tests and other occasions. Metallized film DC support capacitors used in flexible DC transmission, because they support the IGBT DC voltage in the circuit, require The ESL (equivalent series inductance) inside the DC support capacitor should be as small as possible, otherwise it will directly affect the operation safety of the IGBT. According to the operation requirements of the system, the ESL inside the DC support capacitor must reach a certain specific value in order to ensure the safety of operation. [0003] At present, there is no good way t...

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Problems solved by technology

[0005] (1) Use an oscilloscope to measure the discharge oscillation frequency and logarithmic attenuation rate of the capacitor, and calculate the capacitor ESL according to the corresponding formula. This method also brings the additional inductance value of the external circuit into the measured value during the test, and it is impossible to distinguish the metallization alone. The specific value of ESL inside the film capacitor

[0006] (2) Use the difference method to measure the inductance value of the capacitor. This method requires that the inductance value of the external circuit must be on the same order of magnitude as the capacitor ESL, and the ESL of metallized film capacitors such as DC support capacitors, locomotive capacitors, and pulse capacitors is basically tens of nH, it is basically impossible to control the inductance value of the external circuit at the nH level

[0007] (3) Calculate the ESL by measuring the resonant frequency of the capacitor and calculate the ESL by measuring the capacitance value under the power frequency and high frequency (105-107Hz) voltage. These two methods are based on the current actual test conditions. To achieve the measurement of the resonant frequency of the capacitor and to obtain high frequency power supply, it is very difficult

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