NEMA XXX

NEMA XXX is the electrical-grade paper phenolic laminate — kraft paper and phenolic resin, like NEMA XX, but manufactured to tighter controls on paper purity and resin content to deliver meaningfully higher dielectric strength and insulation resistance.

TL;DR

Chemistry & Reinforcement

Like all paper phenolics, NEMA XXX is built from multiple plies of resin-impregnated kraft paper, pressed under heat and pressure to produce a rigid thermoset laminate. The distinction from NEMA XX lies in raw material selection and process controls:

• Reinforcement: Higher-purity alpha-cellulose kraft paper (lower ash, lower metallic contamination)
• Resin: Phenol-formaldehyde (phenolic), formulated for minimum ionic impurities
• Color/finish: Dark brown, same visual appearance as NEMA XX
• Density: ~1.34 g/cc

The lower ionic content of the paper and resin translates directly to higher volume resistivity and dielectric strength. XXX is the minimum-grade phenolic specified for most low-voltage electrical panel and transformer applications.

Key Properties

Typical Applications

NEMA XXX is the standard electrical insulation phenolic across low-voltage control and transformer applications:

• Terminal and mounting boards — the classic use case. XXX panels route and support bus bars, terminal strips, and wire bundles in motor control centers, switchboards, and distribution panels.
• Transformer coil forms and spacers — phenolic spacers between winding layers in dry-type transformers operating at 250°F or below.
• Relay and contactor mounting plates — low-voltage relay racks and contactor bases in industrial control cabinets.
• Coil forms — bobbin stock for low-voltage solenoids and chokes.
• Electrical panels in consumer appliances — motor control boards for appliance-class motors.
• Low-voltage bus bar supports — spacers and standoffs in 600V-class switchgear where cost matters and ambient temperature is controlled.

Standard Sizes

Tight-tolerance parts (coil forms, precision spacers) may require grinding to ±0.002 in. after cutting from stock.

Standards Reference

1. NEMA LI 1 — Grade XXX defines minimum dielectric strength (450 V/mil at 1/8 in. short-time), water absorption, and mechanical requirements. NEMA LI 1-2020 is the current edition.
2. MIL-I-24768/13 — Military specification for paper-base phenolic electrical grade (Type PBE — Paper-Base, Electrical). QPL certification required for military procurement.
3. ASTM D709 — covers test methods and grades for all laminated thermosetting materials; the testing backbone behind NEMA LI 1 values.

Comparison to Neighbor Grades

Choose XXX when: you need both electrical insulation and structural support in a single low-cost laminate, and punching production is not required. Choose XXX-P when the same part must be punched hot on a production press. Choose XXX-PC when punching must occur at room temperature.

More related guides

Other paper phenolic grades

• NEMA XX Mechanical Grade
• NEMA XXX-P Post-Formable
• NEMA XXX-PC Cold-Punch

Step up in electrical performance

• Canvas Phenolic CE
• Linen Phenolic LE
• Glass Phenolic G3

All grades index

• NEMA Grades Directory