There are several reasons to use a capacitor bank:
- Power-Factor Correction: This is the primary reason for AC electrical systems. Capacitor banks are employed for power-factor correction in AC power supplies, such as transformers and electric motors. They help address power-factor lag or phase shift, which is the ratio of useful work performed to the maximum work that could be done at the supplied voltage and amperage. Power-factor correction capacitors counteract the inductive loading caused by devices like electric motors and transmission lines, making the load appear more resistive. This improves the current-carrying capacity of the system and allows for additional loads to be added without altering the apparent power.
- Shunt Capacitor: Capacitor banks can be used as shunt elements to redirect high-frequency noise to ground, preventing it from propagating through the system. This helps improve the electrical supply quality, particularly at the load, and enhances the efficiency of power systems.
- Energy Storage: Capacitor banks, like individual capacitors, can store electrical energy when connected to a charging circuit and release it when discharged. They are used in electronic devices to maintain power supply during battery changes. In modern consumer devices like mobile phones, high storage capacity in a small volume is required. However, increasing capacitance typically requires larger plate areas, which presents a challenge due to limited space. Typically, for AC energy storage, supercapacitors are used and it will require a inverter circuit and complex control systems. These kind of systems are good for short term UPS (less than 5 minutes) while awaiting for generator sets (typically diesel fired) to start-up in the event of power fail.
In summary, capacitor banks find applications in power-factor correction, noise bypass, and energy storage for DC systems, contributing to improved electrical supply quality, increased efficiency, and enhanced power system performance.