Film capacitors’environmental resistance ability and voltage and current testing

1. Environmental resistance ability test

2.1 Temperature shock test

The temperature shock test is to determine the capacitor's ability to be exposed to high and low temperature extremes and to resist the alternating shock of high and low temperature extremes through the rapid change of ambient temperature. The temperature shock test usually adopts the following conditions:

Test temperature: -55℃～85℃;

Constant temperature time: 30 minutes;

Conversion time: ≤5 minutes;

Number of cycles: 50 times;

Test requirements: The test chamber should have sufficient heat capacity so that after the test sample is placed in the test chamber, the working space can return to the specified temperature value within 5 minutes.

2.2 Withstand voltage test

The dielectric withstand voltage test is to apply a specified voltage between mutually insulated parts or between an insulated part and the ground for a specified time to determine whether the capacitor can work safely at the rated voltage;Whether the capacitor can withstand overpotential caused by switching, surge and other similar phenomena, so as to assess whether the capacitor insulation material or insulation gap is suitable.If the capacitor is defective, it will inevitably produce breakdown discharge or damage after the test voltage is applied. Breakdown discharge is manifested as arcing, spark discharge or breakdown. Excessive leakage current may cause changes in electrical parameters or physical properties.

During the design and production process of capacitors, the breakdown voltage that the dielectric film should withstand is generally 3 to 5 times the rated voltage. Therefore, organic film capacitors with reliability indicators can withstand the impact of impulse voltages that exceed the rated voltage. The withstand voltage test can be used to assess the withstand voltage capability and consistency of the withstand voltage performance of the capacitor. The withstand voltage test conditions are as follows:

Test voltage: UR, 1.1UR, 1.2UR, 1.3UR, 1.4UR, 1.5UR;

Ambient temperature: 25℃;

Pressure time: 60 seconds;

Voltage property: DC;

Test requirements: The pulse component of the test voltage shall not exceed 5% of the RMS value. The power supply power and output impedance shall ensure that there is no significant waveform distortion and significant voltage change under various test loads.

2.3 Vibration test

Vibration can loosen the capacitor structure and cause relative movement of internal components. Vibration can cause solder joints to fall off, poor contact, and deterioration of working characteristics. Vibration can also cause capacitors to produce noise, wear, physical failure, and even structural fatigue. The specific test conditions are as follows:

Vibration frequency range: 10~2000Hz;

Displacement amplitude: 0.75mm;

Acceleration: 100g;

Crossover frequency: 70.7Hz;

Number of sweeps: 12 times in each of the 3 directions;

Time: 12 hours in total

2.4 Impact test

The impact test is to simulate the adaptability of capacitors to non-repetitive impacts that they may be subjected to during transportation, handling and whole machine operation. The specific test conditions are:

Impact: 50g;

Nominal pulse duration: 11ms;

Waveform: half-sine;

Velocity change: 3.44m/s;

Impact direction and number: Three impacts are applied to each of the six directions of the three mutually perpendicular axes of the test sample (a total of 18 times)

2.5 Humidity resistance test

The humidity resistance test is an accelerated method to evaluate the ability of components and materials to resist the effects of humidity degradation under typical tropical and subtropical high temperature and high humidity conditions. The specific test conditions are as follows:

Cycle steps: Step 1: The temperature in the test chamber should rise from 25°C to 65°C within 2.5 hours. During this period, the relative humidity is 90% to 100%;

Step 2: Keep the temperature at 65°C and the relative humidity at 90% to 100% for 3 hours;

Step 3: The temperature in the test chamber should drop to 25°C within 2.5 hours, and the relative humidity should be 80% to 100%;

Step 4: Starting from the 8th hour, the temperature in the test chamber should rise from 25°C to 65°C within 2.5 hours. During this period, the relative humidity should be 90% to 100%;

Step 5: Keep the temperature at 65°C and the relative humidity at 90% to 100% for 3 hours;

Step 6: The temperature in the test chamber should drop to 25°C within 2.5 hours, and the relative humidity should be 80% to 100%;

Step 7: Keep the temperature at 25°C and the relative humidity at 90% to 100% until the end of the cycle at the 24th hour.

Number of cycles: 10 times

Based on the main application fields, main failure modes, classification of pulse discharge and current research status of environmental testing of organic film energy storage pulse capacitors, a test procedure that is more in line with the current production and application of organic film energy storage pulse capacitors was selected.

2.Current withstand ability test

2.1 Short circuit discharge test

The short-circuit discharge test is to achieve the equivalent value of the test within an extreme discharge state. This can be achieved by adopting the short-circuit discharge test: different working voltages are applied and the discharge circuit load is zero.

Short-circuit discharge test conditions:

Test voltage: 1 times rated voltage, 1.1 times rated voltage, 1.2 times rated voltage, 1.5 times rated voltage;

Test temperature: 25℃;

Charging time: 6s~10s;

Discharge rise time: 150ns~300ns;

Discharge times: 500 times, 1000 times, 1500 times, 2000 times, 2500 times, 3000 times, 3500 times, 4000 times.

Test requirements: Take samples and apply 1 times, 1.1 times, 1.2 times, 1.5 times rated voltage respectively;

Before the capacitor life test, the capacitance and loss are tested; during the test, the capacitance and loss are tested every 500 times. During the test, the discharge circuit is kept unchanged, and the discharge current is monitored every 500 times using an oscilloscope and a current sensing loop.

2.2 Load Discharge

The load discharge test is to achieve the equivalent value of the test within an actual discharge number framework. This can be achieved by applying the rated voltage and using different external loads (different loads will directly affect the discharge rise time) to perform a load discharge test.

Load discharge test conditions:

Test voltage: rated voltage

Test temperature: 25℃

Charging time: 6s~10s

Discharge rise time: 1ms, 2ms, 5ms, 10ms

Discharge times: 10,000 times

Test requirements: Take samples and apply rated voltage respectively, and discharge with different loads. When discharging, the discharge waveform rising edge time is: 1ms, 2ms, 5ms, 10ms, 20ms. Before the capacitor life test, the capacitance and loss are tested; during the test, the capacitance and loss are tested every 500 times. During the test, the discharge circuit is kept unchanged, and the discharge current is monitored every 500 times with an oscilloscope and current induction loop.