OVC III vs. OVC IV: How to Select the Right Category for Industrial Applications

OVC III vs. OVC IV: How to Select the Right Category for Industrial Applications

In modern industrial power system design, choosing the correct Overvoltage Category (OVC) is critical. With the rise of Industry 4.0 and the widespread adoption of automation equipment, more and more applications require higher levels of overvoltage protection. This article explores the differences between OVC III and OVC IV to help engineers select the appropriate power category.

☑ What is Overvoltage Category (OVC)?

Overvoltage Category (OVC) is a classification defined by the IEC 60664-1 standard. It describes the level of transient overvoltage (e.g., lightning surges, switching spikes) that electrical equipment must withstand in its installed environment. The higher the category, the closer the equipment is to the power source, and the greater the electrical stress it may encounter.

OVC Classification Standards

According to IEC 60664-1, Overvoltage Categories are classified into four levels:

• OVC I：Applies to electronic circuits in controlled environments; not intended for direct connection to the mains supply.
• OVC II：Typical for household appliances and handheld tools powered through wall outlets.
• OVC III：Intended for fixed installations such as industrial equipment directly connected to the building's distribution system.
• OVC IV： Applies to equipment located at the origin of the electrical installation, such as electric meters and primary overcurrent protection devices, which must withstand the highest level of transient overvoltages.

☑ Why is OVC rating critical to impulse withstand voltage?

IEC 60664-1 specifies the Rated Impulse Voltage requirements for each Overvoltage Category (OVC) at various nominal operating voltages. These requirements are essential not only for ensuring the safety and reliability of equipment but also for meeting international certifications such as CB and UL.

☑ Rated Impulse Voltage by OVC Level (unit: V)

During the selection process, it's crucial to consider the actual installation environment and the required OVC level to ensure system safety, durability, and regulatory compliance.

☑ OVC II vs. OVC III vs. OVC IV: Understanding Design Differences at a Glance

When power modules are used in higher OVC-rated environments, it's not merely a label upgrade — it reflects more stringent safety, insulation, and design requirements.

The following table highlights the key differences in design and testing standards among OVC II, OVC III, and OVC IV:

 Key Design Insights

Increased Clearance Distance:

Higher OVC ratings require longer insulation distances. This means PCB layout must accommodate larger creepage and clearance distances to prevent discharge, especially in humid environments.

Higher Dielectric and Surge Withstand Requirements:

To pass higher voltage withstand and impulse tests, power modules must use transformers, insulation materials, and capacitors rated for higher voltages.

Upgraded Safety Components:

Transitioning from X2 to X1 capacitors, and from a single Y1 capacitor to dual Y1s, is essential to cope with high-energy disturbances in OVC III/IV environments.

☑ Industrial Application Recommendations: Choosing OVC III or OVC IV

☑ High Altitude Consideration

Most OVC III power modules are rated up to 2000 meters above sea level. At higher altitudes, thinner air reduces dielectric strength, which may require derating the OVC level to OVC II or reinforcing insulation design.

☑ Cost and System Optimization Analysis

☑ ARCH Electronics Product Line: Robust Options for OVC III & IV

ARCH Electronics offers a wide selection of high-performance power modules compliant with OVC III and OVC IV, ranging from 20W to 1000W. A variety of package types are available, including PCB-mount encapsulated power modules and switching power supplies, tailored for diverse industrial and energy applications.

☑ Conclusion: Choose the Right OVC Level to Strengthen System Resilience

Selecting the appropriate Overvoltage Category (OVC) in power system design is not only essential for equipment safety, but also has a direct impact on system cost and engineering complexity.

ARCH Electronics is committed to delivering highly reliable, efficient, and internationally certified OVC-compliant power solutions—helping you build smarter, more resilient systems for demanding industrial applications.

Explore More ARCH AC-DC Power Solutions: Visit Our Product Page

Contact Us:sales@archcorp.com.tw