Views:1 Author:Site Editor Publish Time: 2021-05-10 Origin:Site
With the rapid development of power electronics technology, the application range of metallized capacitors has become wider and wider, such as various inverters, UPS and SVG power supplies, solar and wind power generation systems, hybrid and pure electric vehicles and other new energy fields. Capacitors for filtering and absorbing protection all use thin-film metallization structures, and high-specific energy pulse capacitors have also begun to develop towards metallization.
Power electronic capacitors are usually used in non-power frequency applications. Their peak current resistance and impact current resistance are key technical parameters. Since current resistance is the weakest link of metallized film capacitors, products with this index must have current resistance. Test assessment. A high-power electronic switch is used to form a capacitor charging and discharging circuit, and the discharge current, current attenuation cycle and current and voltage change rate are quantitatively controlled by adjusting the charging voltage or discharge circuit parameters. The test method is fast, simple, and practical. It is a film capacitor for design verification and verification.Effective means of quality control.
The severity of the current impulse test is mainly determined by the following parameters:
1. Large discharge current value, its peak value depends on the charging voltage and the impedance of the discharge circuit.
2. The current rate of change (di/d1) is mainly determined by the inductance L of the discharge circuit. The smaller the inductance L, the higher the current rate of change.
3. The decay oscillation frequency f of the discharge current depends on the measured capacitance C and the loop inductance L.
4. The discharge current cycle count is based on the resistance R of the discharge circuit. Under the same current peak value and change rate, the cycle number is higher, and the severity is higher.
Therefore, we conduct current impulse tests on these parameters:
1. Set the charging voltage value U, the voltage value determines the peak value of the discharge current, I=U/R.
2. Set the charging time. Determine the charging time according to the capacitor capacity C under test, the internal resistance r of the charging power supply and the required voltage U.
3. The charging switch s is controlled by an adjustable time relay, S is closed, and the adjustable DC power supply E charges the test capacitor C.
4. When the charging time is up, S is turned on and charging is over, the control circuit sends a pulse to the SCR SCR, the SCR is turned on, and the capacitor C starts to discharge.
5. Due to the resistance and inductance of the discharge circuit, the discharge process is oscillating attenuation. After a few weeks, the oscillating ends, and the current is zero. The SCR is turned off. The cycle time from the beginning of the oscillation to the end is generally much less than 1 s.
6. After the discharge is over, the charging switch is closed to start charging again, and the above test is repeated.
The above is the content of the current impact test of the film capacitor.