Electrical Insulation: Materials, Ratings and the Products Wedge Supplies (2027 Guide)

Electrical insulation is the material that keeps current where it belongs — between conductors, between live parts and earth, and between equipment and the people who operate it. In a switchboard, a motor, a furnace or an EV battery pack the insulation is doing two jobs at once: blocking voltage and surviving heat, arcing, vibration and chemicals for the life of the equipment.

This guide explains how electrical insulation is rated, compares the common insulation materials, and sets out the electrical insulation products Wedge Industries Limited supplies from India — led by the WedgeMICA mica range rated to 1100 °C, 23.6 kV/mm and UL 94 V-0.

What electrical insulation has to do

An insulator is judged on a handful of properties, and the right product is the one that meets all of them at the operating temperature, not just at 20 °C in the catalogue:

Property	What it means	Typical value — mica laminate
Dielectric strength	Voltage per mm of thickness before breakdown	19.7–23.6 kV/mm minimum (WedgeMICA WMB); natural mica film 40–80 kV/mm
Volume resistivity	Resistance to leakage current through the bulk	Natural muscovite 4×10¹³ – 2×10¹⁷ Ω·cm
Dielectric loss (tan δ)	Energy lost as heat under AC — matters in HV and HF service	Muscovite 0.1–0.4 × 10⁻³; phlogopite 1–5 × 10⁻³
Arc resistance	Seconds an arc can play on the surface before a conductive track forms	420–500 s (mica) vs 120–130 s (G10 / FR4)
Thermal endurance	Highest continuous temperature at which the material keeps insulating	550 / 800 / 1100 °C by mica grade
Flammability	Behaviour when ignited	UL 94 V-0 on all WedgeMICA rigid grades
Mechanical strength	Resists bolting, vibration and electromagnetic forces	Tensile 110–195 MPa, shear 207 MPa (WMB boards)

Thermal classes of electrical insulation

IEC 60085 groups insulation systems by the temperature they can run at continuously: Class Y 90 °C, A 105 °C, E 120 °C, B 130 °C, F 155 °C, H 180 °C, N 200 °C, R 220 °C and 250 °C. Most polymer films, varnishes and glass-epoxy laminates stop at Class H or N. Anything hotter — furnace coils, arc chutes, heating elements, molten-metal plant — is mica, ceramic or glass territory, which is where the WedgeMICA range sits.

Electrical insulation materials compared

Material	Continuous temperature	Dielectric strength	Arc resistance	Machinable?	Best for
Mica laminate (WedgeMICA WMB)	550 / 800 / 1100 °C	19.7–23.6 kV/mm min.	420–500 s	Yes — CNC, stamp, drill	Heat + voltage + arcing: switchgear, furnaces, heaters
Natural sheet mica	500–900 °C (mineral)	40–80 kV/mm (thin film)	High	Cut, punch	Gauge-glass shields, capacitors, transistor washers
G10 / FR4 glass-epoxy	about 130 °C	19.7–21.7 kV/mm	120–130 s	Yes	Ambient-temperature panel parts, PCBs
Polyester / polyimide film	about 130 °C / 240 °C	High per µm	Low	Cut, wrap	Slot liners, wire wrap, flexible insulation
PTFE and fluoropolymers	about 260 °C	High	Good	Yes	Chemical and HF service
Ceramics (alumina, steatite, porcelain)	1000 °C+	High	Very high	No — fired to shape	Bushings, standoffs, HV insulators
Silicone rubber / EPDM	about 180–200 °C	Moderate	Good tracking	Mould	Cable, flexible HV covers

Values for non-mica materials are typical published ranges for comparison only. The pattern is clear: polymers win on cost and flexibility below 200 °C, ceramics win on temperature but cannot be machined, and mica is the only sheet material that gives high dielectric strength, arc resistance and 550–1100 °C service while still being cut, drilled and stamped in a normal workshop.

Electrical insulation products from Wedge Industries Limited

Rigid boards and sheets

• Rigid mica board / mica sheet — WMB-M550, WMB-P800, WMB-S1100; 1–50 mm; 1000×1200 and 1000×2400 mm. The workhorse for arc chutes, phase barriers, busbar supports and furnace panels.
• Mica heater plates — thin rigid sheet 0.15–1.5 mm for heating elements, appliances and industrial heaters.
• Corrugated mica plates — spacing and supporting resistance coils in high-watt-density heaters.

Flexible sheets, rolls, papers and tapes

• Flexible mica sheet — WMF-M500 / WMF-P600, 0.15–5 mm, for motor slot liners, coil wraps, transformers and circuit breakers.
• Mica roll for induction furnaces — glass-, polyester- or ceramic-backed mica paper, 0.2–5 mm, the slip plane between crucible and coil.
• Muscovite mica paper and phlogopite mica paper — the reconstituted dielectric web behind every laminate and tape.
• Glass mica tape, muscovite mica tape, phlogopite fire-resistant mica tape and synthetic mica tape — for fire-resistant cables and coil insulation.

Tubes, bushes, gaskets and machined parts

• Mica tubes and bushes — ID from 8 mm, length to 1000 mm, four grades from 130 °C to 1100 °C, for bolt, stud and terminal insulation.
• Mica gasket sheet — phlogopite, plain or stainless-steel reinforced, for hot flanges where the gasket must also insulate.
• Machined mica parts to drawing — arc barriers, washers, rings, spacers, collars, slotted coil supports and terminal plates, supplied under SKU WMX-[grade]-[drawing no.], counted and labelled.

Natural mica and electronics

• Natural ruby muscovite mica — blocks, splittings, strips, discs, washers and gauge-glass shields in visual qualities V1–V6, from the Giridih mica belt.
• Transistor mica insulator plates (TO-3 / TO-220) — the thin, electrically isolating, thermally conductive pad between a power semiconductor and its heatsink.
• Condenser mica films — precision-split films for capacitors and optical windows; gauge glass mica and mica shields for boilers and process sight glasses.

EV and battery energy storage

• EV busbar and module mica insulation sheet — die-cut 0.15–1 mm sheet for busbar wrap, module wall lining and high-voltage creepage barriers.
• EV battery mica barrier plate — die-cut phlogopite plates that contain thermal runaway between cells, over modules and under pack lids.
• Aerogel thermal runaway pads and fire barriers — paired with mica where a thin, very low-conductivity layer is needed next to the electrical barrier; see the aerogel for BESS guide.

Powders and fillers

• Wet ground mica powder 325 mesh and calcined mica powder — dielectric fillers for insulating coatings, compounds and welding electrodes.

Every product above sits in the electrical insulation category; the mica families are detailed in the WedgeMICA catalogue (PDF).

Electrical insulation by application

Application	Duty	Wedge product
LV / MV switchgear — arc chutes, splitter plates, phase barriers	Arc plasma, 420+ s arc resistance, mechanical shock	Rigid mica board WMB-M550 / WMB-S1100, machined parts
Busbar supports and standoffs	Electromagnetic forces, heat from the bar, creepage	WMB-M550 board, mica tubes WMT-M550, EV busbar sheet
Induction furnaces	Coil clamp bolts, spacers, panels, slip plane at 800 °C	WMB-P800 board, WMT-P800 tubes, WMR mica rolls
EAF / LF and smelting	Electrode clamp, mast arm, bus tube, anode clamp insulation	WMB-P800 / WMB-S1100 machined parts
Motors, generators, transformers	Slot liners, coil wraps, phase separation, stud bushes	Flexible mica sheet WMF, mica tapes, mica tubes
Heating elements and appliances	Element support at 550–1100 °C	Heater mica plates WMH, corrugated plates
Power electronics	Isolation between semiconductor and heatsink	Transistor mica insulators TO-3 / TO-220
EV and BESS packs	HV creepage barriers plus thermal runaway containment	EV mica sheet, mica barrier plates, aerogel pads
Boilers and process plant	Transparent, steam-resistant gauge protection	Gauge glass mica, mica shields
Fire-resistant cables	Circuit integrity in fire	Glass / phlogopite / synthetic mica tapes

How to select electrical insulation

1. Start with temperature. Continuous operating temperature at the part, including hot spots, decides the material family. Below 130 °C glass-epoxy and films are economical; above it, move to mica or ceramic.
2. Add the electrical duty. System voltage sets the thickness through dielectric strength; the presence of arcing or tracking risk (switchgear, contactors) favours mica over glass-epoxy.
3. Check the mechanical load. Bolted supports and parts under electromagnetic force need the 195 MPa tensile strength of muscovite board; coil wraps need flexible sheet.
4. Decide the form. Sheet to cut on site, stamped plates, wound tubes, or finished machined parts to drawing — the last option removes mica dust and cutting from your line.
5. Specify by SKU. WedgeMICA parts are ordered as family-grade-thickness-size, for example WMB-P800-10-1012 (phlogopite rigid board, 10 mm, 1000 × 1200 mm), or WMX-P800-D1042 for a machined part against drawing D1042.

Electrical insulation price and ordering (2027)

Electrical insulation materials are priced by material, grade, thickness, sheet size or drawing and quantity, so Wedge Industries Limited quotes each enquiry in ₹ INR and $ USD rather than publishing list prices. As a rule muscovite grades cost less than phlogopite, which cost less than synthetic mica; boards are priced per sheet or per kg, papers and tapes per roll, and machined parts per piece.

A Technical Data Sheet comes with every quotation, a Material Test Certificate with batch test values with every delivery, and samples are available for evaluation before bulk orders. MOQ and lead time are confirmed with each quotation; export orders are packed flat on pallets or in wooden cases and shipped to 45+ countries.

Get PriceDownload the WedgeMICA catalogue (PDF)

Electrical insulation FAQs

Related pages

• Electrical insulation products — full category
• Mica insulation — WedgeMICA range and selection guide · Mica insulation guide 2027
• EV battery insulation and thermal runaway barriers · BESS in India 2027 guide
• High-temperature insulation · Passive fire protection