Why Capacitors Can Be Broken Down

Ⅰ.Causes of Power Capacitor Breakdown:

 

Overvoltage: Power capacitors have an upper limit for rated voltage. When the system voltage is excessively high or experiences transient overvoltages (such as lightning strikes, switching surges, etc.), the internal electric field strength of the capacitor can exceed the withstand capability of its insulating material, leading to insulation breakdown.

Harmonic Influence: Capacitors are highly sensitive to high-frequency currents (harmonics). Especially in environments with a large number of non-linear loads, harmonic currents in the system can cause increased internal heating and accelerated insulation aging within the capacitor, which may ultimately lead to breakdown.

Aging of Insulating Material: The internal insulating dielectric of a capacitor gradually ages over time and under operating conditions (such as temperature, voltage fluctuations), leading to a decline in insulation performance. Aged dielectric is prone to minor discharges when under voltage; the cumulative effect of these discharges can eventually cause dielectric breakdown.

Poor Installation Environment: High temperature, high humidity, or dusty environments can accelerate the aging of the capacitor's internal insulation and may trigger partial discharges and breakdown. For example, excessively high temperatures increase the capacitor's operating current, thereby intensifying heat generation and potentially leading to breakdown.

Manufacturing Defects: If there are process flaws during the capacitor's manufacturing (such as uneven dielectric, poor welding of conductive foils or leads, etc.), they may cause partial discharges or short circuits during operation, leading to breakdown.

Overcurrent: Capacitors are designed with a rated current. If the system current exceeds this limit, causing the capacitor to operate under sustained overcurrent conditions, severe internal heating will occur. The insulating material, subjected to long-term high temperature and high pressure, becomes more susceptible to breakdown.

 

II. To Prevent Capacitor Breakdown, the Following Measures Are Recommended:

Use appropriate overvoltage protection devices.

Install filtering equipment to suppress harmonics.

Select high-quality, reliable capacitors that meet the system's voltage and current requirements.

Regularly inspect and maintain capacitors to ensure they operate in a good environment.