● Introduction
When engineers evaluate LAN transformers for Ethernet applications, one specification consistently appears on datasheets: Isolation Voltage. Also called dielectric withstand voltage or “Hi-Pot” rating, this parameter is essential for ensuring electrical safety, compliance with IEEE standards, and long-term reliability. In this article, we break down what isolation voltage means, why 1500 Vrms is the recognized benchmark, and how LINK-PP designs its LAN transformer portfolio to meet diverse application needs.
● What Is Isolation Voltage?
Isolation voltage describes the maximum alternating voltage that the insulation barrier inside a LAN transformer can withstand between the primary winding (connected to the PHY chip and PCB) and the secondary winding (connected to the RJ45/cable side).
This isolation is critical because:
Protecting devices – prevents surge or fault voltages from reaching the Ethernet PHY and damaging the circuit.
Protecting people – ensures user safety by stopping hazardous voltages from leaking into network equipment.
Maintaining signal integrity – eliminates ground loops and common-mode interference, improving high-speed Ethernet performance.
In practice, isolation voltage is verified through a Hi-Pot test, where the transformer is subjected to a high AC test voltage for a defined duration (commonly 60 seconds).
Standards and Compliance
The IEEE 802.3 Ethernet standard specifies that Ethernet ports must provide at least 1500 Vrms isolation for 60 seconds between the circuit and the line side.
Other safety standards, such as IEC 60950-1 and IEC 62368-1, reinforce similar requirements, especially for commercial and industrial electronics. For more demanding environments—such as outdoor networks, telecom infrastructure, or medical equipment—engineers may specify higher isolation levels (e.g., 2250 Vrms, 3000 Vrms, or higher) to meet additional safety and regulatory requirements.
Practical Guidance for Engineers
When reviewing a transformer datasheet, always confirm:
Isolation Voltage rating (Vrms, test time) – Does it meet IEEE requirements?
Creepage and Clearance Distances – Are PCB Design Rules Followed?
Environmental conditions – Will humidity, temperature, or PoE power stress the insulation?
Certifications – UL, RoHS, and ISO compliance confirm global market readiness.
Application match – Choose higher isolation models for industrial, telecom, or outdoor designs.
Conclusion
Isolation voltage is more than a datasheet number—it’s a safeguard for equipment, users, and signal quality. While 1500 Vrms isolation is sufficient for most Ethernet devices, demanding applications may require higher ratings.
With a broad portfolio of LAN transformers, LINK-PP ensures compliance with IEEE 802.3 while providing engineers with cost-effective, high-performance solutions. Whether you need standard 1500Vrms parts or advanced high-isolation models, LINK-PP delivers components designed for safety, reliability, and long-term network performance.
👉 Explore LINK-PP’s full range of LAN Transformer products to find the right solution for your Ethernet design.
