How DMC Insulators Respond to Updated Safety Requirements for Low-Voltage Electrical Products

Introduction

With the continuous upgrading of electrical safety regulations, low-voltage electrical products such as switchgear, distribution boards, and control panels must comply with stricter requirements related to insulation coordination, fire safety, and thermal stability. International standards such as IEC 60664-1 (Insulation Coordination), IEC 60112 (Comparative Tracking Index test), and fire-safety requirements like UL94 flame-retardant ratings are now widely referenced in national and industry standards for electrical equipment.

As a thermosetting composite material made from unsaturated polyester resin, glass fiber, and fillers, DMC (Dough Molding Compound) insulators provide a balanced combination of electrical insulation, mechanical strength, and environmental resistance. These characteristics allow DMC insulators to meet the evolving safety requirements of modern low-voltage electrical systems.

Material Group Compliance: Tracking Resistance and Insulation Coordination

One of the most important safety indicators for insulating materials in low-voltage equipment is the Comparative Tracking Index (CTI), defined in IEC 60112. The CTI measures the ability of an insulating material to resist electrical tracking caused by moisture, contamination, and electrical stress.

According to IEC 60664-1, insulating materials are divided into four groups based on CTI values:

Material Group	CTI Range
Group I	≥ 600 V
Group II	400–599 V
Group IIIa	175–399 V
Group IIIb	100–174 V

High-quality DMC insulating materials typically achieve CTI ≥ 600 V, which places them in Material Group I, the highest classification.

Why this matters for safety

A higher CTI rating provides several design advantages:

Reduced risk of surface tracking failure

Improved resistance to contamination and humidity

Shorter creepage distances allowed in equipment design

For low-voltage switchgear and busbar support systems, compliance with Material Group I or II significantly improves insulation reliability under pollution conditions defined in IEC standards.

Thermal Resistance: Meeting Long-Term Temperature Requirements

Thermal stability is another key requirement in modern electrical safety standards. Electrical components must withstand continuous operating temperatures and temporary overload heating without degrading insulation performance.

DMC insulators typically provide the following thermal characteristics:

Continuous operating temperature: −40 °C to about 130–135 °C

Relative Thermal Index (RTI): about 130 °C (mechanical) and 105 °C (electrical)

Insulation class: Class B (130 °C) according to insulation system classifications

These values satisfy the thermal endurance requirements commonly applied to low-voltage switchgear and controlgear assemblies, which often follow insulation system classifications similar to IEC and JIS standards.

Practical safety benefits

Stable insulation under high current load
Busbars and terminals generate heat during operation. DMC maintains mechanical strength and dielectric performance even at elevated temperatures.

Reduced risk of insulation aging
Thermosetting polyester resin structures resist thermal deformation and creep better than many thermoplastics.

Compatibility with modern compact equipment
As electrical panels become more compact and heat density increases, high thermal endurance materials are increasingly required.

Flame Retardancy and Fire Safety Compliance

Electrical safety regulations also emphasize fire prevention and self-extinguishing properties of insulating materials.

Most DMC compounds are designed to meet:

UL94 V-0 flame-retardant rating

Glow-wire ignition test up to 960 °C (IEC 60695-2-13)

UL94 V-0 requirements

To meet the UL94 V-0 classification, the material must:

Self-extinguish within 10 seconds

Produce no flaming drips

Prevent fire propagation

These characteristics are particularly important for switchgear enclosures, busbar supports, and power distribution equipment, where insulation materials are located close to live conductors.

Glow-wire test significance

The IEC 60695 glow-wire test simulates overheating caused by faulty electrical connections. Materials that pass the 960 °C glow-wire ignition test demonstrate strong resistance to ignition and flame propagation.

Additional Electrical Safety Properties

Beyond material classification, thermal resistance, and flame retardancy, DMC insulators also provide several electrical properties essential for compliance with low-voltage safety standards:

Typical values include:

Dielectric strength: about 10–17 kV/mm

Surface resistivity: around 10¹³ Ω

Arc resistance: greater than 180 seconds

Water absorption: typically <0.2%

These characteristics help ensure:

Stable insulation performance in humid environments

High resistance to electrical arcing

Long service life in industrial power distribution systems

Why DMC Insulators Are Widely Used in Low-Voltage Equipment

Due to their compliance with modern safety standards, DMC insulators are widely used in:

Low-voltage switchgear assemblies

Busbar support systems

Motor control centers (MCC)

Power distribution cabinets

Industrial control panels

Their combination of high CTI, thermal endurance, and flame retardancy allows designers to meet strict safety regulations while maintaining compact equipment layouts and long-term reliability.

Conclusion

As safety requirements for low-voltage electrical products continue to evolve, insulating materials must provide higher levels of electrical reliability, thermal stability, and fire resistance.

DMC insulators effectively meet these demands by offering:

High CTI values that satisfy IEC insulation material group requirements

Thermal endurance up to Class B (130 °C) for stable operation under load

UL94 V-0 flame retardancy and glow-wire resistance for improved fire safety

Excellent dielectric strength and moisture resistance

These properties make DMC insulators a reliable choice for modern low-voltage electrical systems where safety compliance, durability, and performance are essential.

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