| CPC G01R 31/64 (2020.01) [H01G 4/015 (2013.01); H01G 4/33 (2013.01)] | 6 Claims |
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1. A method for initial self-healing type classification of metallized film capacitors, comprising:
step 1: applying voltages at different voltage ramp rates to metallized film capacitors to be tested, and determining a voltage bearing range of the metallized film capacitors;
step 2: determining, according to corresponding voltages of the metallized film capacitors when initial self-healing occurs and residual voltages after the initial self-healing occurs, corresponding initial self-healing energy of metallized film capacitors when the initial self-healing occurs within the voltage bearing range of the metallized film capacitors;
step 3: establishing an initial self-healing voltage-energy database according to a corresponding relationship between the corresponding initial self-healing voltages of the metallized film capacitor samples when the initial self-healing occurs and the corresponding initial self-healing energy when the initial self-healing occurs; and
step 4: classifying the metallized film capacitors by utilizing the initial self-healing voltage-energy database and combining an initial self-healing recovery condition and subsequent service lives and performance data of the metallized film capacitors; wherein
the initial self-healing voltage-energy database is established according to the corresponding relationship between the initial self-healing voltages and the initial self-healing energy obtained in the step 2, the established initial self-healing voltage-energy database is subjected to a nonlinear fitting method, and it is determined that the initial self-healing voltage and the initial self-healing energy meet a relation of ESHI=aUSHIn, n∈[2,4], where n∈R,
 C0 is a capacitance, β is a square resistance, ƒ(P) is an interlayer pressure function, and α, k are coefficients, so as to define a boundary range of the initial self-healing voltage-energy database;
an external voltage is applied to the metallized film capacitor, and an initial self-healing voltage boundary is defined, wherein 4Unom is an upper boundary, and corresponding initial self-healing energy is ESHI2; 3Unom is a lower boundary, and corresponding initial self-healing energy is ESHI1, and if:
(1) no self-healing occurs within 2Unom˜5Unom, the metallized film capacitor is an A-level capacitor;
(2) the initial self-healing voltage is within 4Unom˜5Unom, the initial self-healing energy is smaller than ESHI2, and after initial self-healing recovery, the voltage can rise to 5Unom at an original voltage ramp rate, the metallized film capacitor is a B-level capacitor, and otherwise, the metallized film capacitor is a C-level capacitor;
in addition to the case that after the initial self-healing recovery, the voltage can rise to 5Unom at the original voltage ramp rate, the voltage can also rise to 5Unom after independent self-healing occurs for several times, the metallized film capacitor is the B-level capacitor, and otherwise, the metallized film capacitor is the C-level capacitor;
(3) the initial self-healing voltage is within 3Unom˜4Unom, the initial self-healing energy is smaller than ESHI1, and after initial self-healing recovery, the voltage can rise to 4Unom at the original voltage ramp rate, the metallized film capacitor is the C-level capacitor, and otherwise, the metallized film capacitor is a D-level capacitor;
in addition to the case that after the initial self-healing recovery, the voltage can rise to 4Unom at the original voltage ramp rate, the voltage can also rise to 4Unom after independent self-healing occurs for several times, the metallized film capacitor is the C-level capacitor, and otherwise, the metallized film capacitor is the D-level capacitor;
(4) the initial self-healing voltage is within 2Unom˜3Unom, and after initial self-healing recovery, the voltage can rise to 3Unom at the original voltage ramp rate, and the metallized film capacitor is the D-level capacitor;
in addition to the case that after the initial self-healing recovery, the voltage can rise to 4Unom at the original voltage ramp rate, the voltage can also rise to 3Unom after independent self-healing occurs for several times, and the metallized film capacitor is the D-level capacitor;
(5) the initial self-healing voltage is within 0˜2Unom, or the initial self-healing occurs in the areas of (1) to (4), the self-healing voltage cannot be recovered, and the metallized film capacitor is an E-level capacitor along with intensive self-healing; and
the service lives of the metallized film capacitors are defined based on the number of times of applying voltages, the metallized film capacitors with different levels are selected for testing the service lives of the samples with different levels under an applicable voltage, voltage ramp rates used when the metallized film capacitors are classified are applied to the metallized film capacitors to enable the voltages to rise to a maximum value of each corresponding level range, and it is determined that the capacitor fails when a capacitance of the capacitor drops by more than 5% or the capacitor is broken down; the A-level and B-level metallized film capacitors are both used in application scenarios with the voltage lower than 1250V, wherein the service life of the A-level sample is 1400 times, the service life of the B-level capacitor is 1000 times, the C-level metallized film capacitor is used in an application scenario with the voltage lower than 1000V, the D-level metallized film capacitor is used in an application scenario with the voltage lower than 750V, the service lives of the C-level capacitor and the D-level capacitor are both 1200 times, and the E-level capacitor is a metallized film capacitor which is irreversibly damaged in the classification process or is unsuitable for a working condition exceeding a rated voltage thereof and thus is not used.
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