IEC 61051-2:2021

Overview

IEC 61051-2:2021 is an internationally recognized standard published by the International Electrotechnical Commission (IEC). It provides a sectional specification specifically for surge suppression varistors used in electronic equipment. This standard applies to metal oxide varistors characterized by symmetrical voltage-current behavior, suitable for connection to any AC or DC power supply system. The standard aims to ensure the reliable protection of sensitive electronic devices against high transient surges.

The focus of IEC 61051-2:2021 is on varistors intended for secondary surge suppression rather than primary protection against direct lightning strikes. These varistors feature metallic terminations and are designed for mounting either as through-hole components or directly onto printed circuit boards (PCBs).

This edition aligns structurally with ISO/IEC directives and harmonizes with IEC 61051-1:2018, introducing preferred voltage ratings for disk and surface-mount device (SMD) varistors and enforcing zero-fault tolerance in certain test schedules to advance quality assurance.

Key Topics

• Scope and Application
  The standard defines characteristics, performance requirements, and testing methods for metal oxide varistors used in voltage surge suppression. It covers varistors with symmetrical voltage-current characteristics used in electronic equipment powered by AC or DC systems.

• Preferred Voltage Ratings
  Two comprehensive lists specify preferred voltage ratings for disk type and SMD varistors, streamlining component selection for engineers and designers.

• Derating Guidelines
  IEC 61051-2:2021 outlines derating principles at elevated temperatures to maintain varistor performance and longevity, including maximum continuous voltage and peak current derating curves.

• Test Procedures and Performance Requirements
  The standard mandates rigorous electrical, climatic, mechanical, and safety tests such as:

  • Varistor voltage verification
  • Leakage current and capacitance measurements
  • Clamping voltage and maximum peak current tests
  • Soldering heat resistance and solderability
  • Damp heat, rapid temperature change, and endurance testing
  • Mechanical robustness including shock and vibration tests
  • Fire hazard resilience (needle flame test)

• Quality Assessment
  A structured quality conformity process is set forth, encompassing qualification approval with zero fault tolerance and periodic inspections to ensure ongoing compliance.

• Marking, Packaging, and Ordering
  The document specifies requirements for clear marking that facilitate traceability, packaging standards to protect varistors during handling, and detailed ordering information to avoid miscommunication.

Applications

IEC 61051-2:2021 varistors are essential components in protecting electronic and sensitive equipment in diverse applications including:

• Consumer electronics requiring robust surge protection against transient voltage spikes.
• Industrial and medical electronic systems subject to fluctuating supply voltages.
• Communication devices needing reliable voltage suppression to maintain signal integrity.
• Power supplies and control circuits operating under both AC and DC conditions.
• Printed circuit boards where through-hole and surface-mounted varistors prevent damage from transient surges.

By adhering to this standard, manufacturers and system integrators can ensure the varistors meet internationally recognized requirements for performance, safety, and reliability in surge suppression.

Related Standards

IEC 61051-2:2021 forms part of the broader IEC 61051 series covering varistors for electronic equipment. Related standards include:

• IEC 61051-1: General requirements for varistors including quality assessment procedures and measuring methods.
• IEC 61051-3: Specifications for varistors used as primary lightning surge protectors.
• ISO/IEC Directives, Part 2: Guidelines on the structure and drafting of international standards.
• Additional international standards covering electrical component testing, solderability, and climate testing relevant to varistors.

Professionals working with surge suppression devices are encouraged to consult these complementary standards to ensure comprehensive compliance and product excellence.

By implementing IEC 61051-2:2021, manufacturers and engineers achieve enhanced protection against transient voltage surges, ensuring the durability and safety of modern electronic systems while aligning with global quality and safety standards.