How to Select the Right Jianghai Capacitor for Your Inverter Application

Choosing the right capacitors for a power inverter is one of the most critical design decisions. The DC-Link capacitor, in particular, handles immense electrical stress and is often a key determinant of the inverter's overall reliability and lifespan. This guide will walk you through the key considerations for selecting both DC-Link and auxiliary power capacitors from the Jianghai portfolio.

Step 1: Define Your DC-Link Requirements

The DC-Link capacitor's primary role is to stabilize the DC bus voltage and provide a low-impedance path for high-frequency ripple currents. Key parameters to define are:

• DC Bus Voltage (Vdc): The nominal operating voltage of the DC bus. You must select a capacitor with a rated voltage sufficiently higher than this (typically a 20-25% margin).
• Required Capacitance (C): Determined by the allowable DC voltage ripple (ΔV). A larger capacitance results in lower voltage ripple.
• RMS Ripple Current (Irms): This is the most critical parameter for lifetime. You must calculate the RMS value of the current flowing through the capacitor. This value is highly dependent on your modulation strategy and load.

Step 2: Choosing Between Film and Electrolytic Capacitors

For the DC-Link, you have two main choices: Aluminum Electrolytic or Film Capacitors.

Aluminum Electrolytic Capacitors (like the Jianghai CD 130 Screw Terminal series) offer the highest capacitance per unit volume and are very cost-effective. They are excellent for applications where bulk capacitance is the primary need. However, their lifetime is finite and heavily dependent on temperature and ripple current.

Film Capacitors (like the Jianghai CBB 131 series) offer a much longer operational life, superior ripple current handling per µF, and extremely low ESR. They also feature a "self-healing" property, making them exceptionally reliable. While bulkier and more expensive per µF, they are often the superior choice for high-reliability, long-life applications like solar inverters.

Step 3: Lifetime Calculation

For electrolytic capacitors, the lifetime must be carefully estimated. The lifetime provided in the datasheet (e.g., 5000 hours @ 105°C) is a starting point. The actual lifetime in your application (L_op) can be estimated using the following formula, which accounts for operating temperature (T_op) and applied ripple current (I_op):

L_op = L_rated * 2^((T_rated - T_op) / 10) * K_ripple

Where K_ripple is a factor related to the ratio of applied ripple to rated ripple. For accurate calculations, it is essential to consult the manufacturer's specific guidelines or contact our technical support team.

Conclusion

Selecting the right capacitor is a multi-faceted process involving electrical, thermal, and mechanical considerations. By carefully defining your requirements and understanding the trade-offs between different capacitor technologies, you can leverage Jianghai's extensive portfolio to build a highly reliable and efficient inverter. For detailed simulations and personalized recommendations, we encourage you to contact our FAE team.