As electric vehicle (EV) sales continue to increase in the U.S. and other regions, there's also a growing need for EV charging ports. In fact, charging ports have become requisite for new building construction in many regions in order to expand the EV charging infrastructure. However, components used for EV chargers as part of a building installation must be able to withstand transient voltages that can occur when connected to the mains power at the site.
The AC-DC auxiliary power supplies necessary for wall-box chargers and charging stations are no exception. Here's an overview of overvoltage categories, along with characteristics to look for in AC-DC auxiliary power supplies that are appropriate for EV charger applications.
Overvoltage Categories
The severity of transients can vary based on the electrical equipment's distance from a utility source, and various devices have different reliability and availability requirements. For these reasons, the International Electrotechnical Commission (IEC) established the following overvoltage categories (OVC), also known as installation categories:
- OVC I: This is the lowest OVC category level. OVC I applies to equipment connected to low-voltage circuits having measures taken that limit transient overvoltage to a non-hazardous level.
- OVC II: This category covers equipment whose energy supply comes from a fixed installation. Various household items — such as televisions or power tools — that plug into 115 or 230V AC outlets fall into OVC II. In addition, wiring circuits have their own impedances that lower transient voltages further.
- OVC III: This applies to equipment in fixed installations such as machinery hard-wired to the AC supply or where equipment is subject to special requirements. Wall-box and EV charging stations are included in this category, and their power supplies must meet OVC III requirements. Voltage transients can also be reduced via wiring impedance, fuses and circuit breakers.
- OVC IV: The most stringent overvoltage category, OVC IV pertains to equipment nearest to the utility power source where the highest transient voltages tend to occur.
OVC III environments often sustain surges and transients caused by lightning strikes, and power supplies must be designed to resist these threats. For example, OVC III-compliant power supplies with a working voltage up to 300V (nominal) must tolerate up to 4,000V AC transients.
Here's how Daburn Electronics' Polytron PFEV family AC-DC power supplies satisfy OVC III requirements, making them an attractive choice for outdoor EV battery charging stations. These Isolation Class II power supplies — available in versions ranging from 20 to 150 watts — offer a universal input rating of 90 to 264V AC with 4,300V AC I/O isolation and compliance to the EN 61558 safety requirement at up to 2,000 meters altitude. No-load power consumption is <0.10W (<0.15W for the PFEV15).
Additional features and advantages include:
- EMC compliance without external components.
- High efficiency up to 93.5 percent.
- Meets UL/IEC/EN 62368-1, IEC/EN 61558-1, IEC/EN 61558-2-16 and IEC/EN 60335-1.
When you need an AC-DC auxiliary power supply that can withstand transient voltages in EV charger installations, an OVC III-compliant unit — such as the PFEV family — can help ensure safety and reliability.
For more information about PFEV AC-DC power supplies for EV charging applications, visit our product page.