How do I select capacitors for smart meter applications?

James Lewis

Tuesday, May 3rd, 2016

capacitors smart meters

Environmentally-friendly technologies such as the smart grid, renewable energy, industrial inverters and hybrid/electric vehicles are critical to meeting important energy reduction targets. This need is driving an increasing demand for smart energy meters. To assure a long life their components, such as film capacitors, must be able to withstand harsh environmental conditions for 15 years or more.

The EU is planning to install 200 million smart meters to achieve its 2020 energy goals. Cost is a top factor that will determine uptake. Low-cost capacitive power supplies are used to meet these cost goals.

Capacitive power supplies rely on the impedance of the capacitor inserted between it and the AC line. The capacitance must be stable during the life of the device since. Its value determines the impedance of the circuit and, by extension, the voltage fed to the rest of the circuit.

XY SAFETY CAPACITORS-4p

When working with mains, either ‘in series’ or ‘across the line’, metallized film capacitors are the preferred technology. The self-healing capability of X2 safety-rated film capacitors enables safe operation and reliability even when exposed to AC line voltage spikes up to 2.5 kV.

In a capacitive power supply, reduced capacitance prevents the circuit from delivering adequate current to the load. In an X or Y circuit, reduced capacitance impairs EMI attenuation, exposing other components to potential signal interference. Also, an increase in the capacitor’s dissipation factor may lead to overheating that can cause premature self-heating, further damaging the capacitor. These losses mean a faster time to failure for the entire system.

KEMET sought a solution based on improved materials. The challenge was to create a more robust capacitor technology practical for use in equipment such as smart meters and solar generators. In collaboration with academic research groups, KEMET developed the new F862 series using a high-quality polypropylene film as the dielectric alongside an improved production process.

By introducing this new technology to the proven X2 capacitors, new ultra-robust film capacitors were created in the form of a new series. Lifetime ratings over 15 years are now achievable in high humidity environments compared to standard polypropylene or polyester film capacitors that had lifetimes of only 2-3 years.

Polypropylene assures optimum self-healing and significantly enhances tolerance high-frequency ripple currents as well as meeting the requirements for control of battery charging in plug-in hybrids and electric vehicles (PHEVs/EVs).

Learn more about capacitors for smart meters

In a previous post we talked about the F862 as an Elektra Finalist. You can also watch an introduction to the F862 video from Mouser.