MV/HV Fuse Body Tubes: Matching Material to Voltage Class and Arc Duty
The fuse body is not a housing. It is the arc chamber, the pressure vessel and the structural member at the same time, and the material has to be chosen for the clearing duty before the drawing is fixed.
The short answer
- Two questions decide the material: does the surface face the arc, and what is the breaking duty? Everything else follows.
- Arc-facing surfaces need a gas-generating or ablative material. Vulcanized fiber is a structural and end-cap material, not an arc-facing liner. This is the mistake we correct most often.
- 1 kV to 36 kV is covered by four families: vulcanized fiber for non-arc structural bodies, vulcanized fiber plus fiberglass composite for cutout and expulsion tubes, G5/G9 melamine for LV and HRC bodies, and G10/G11 epoxy glass or filament wound tube for HV current-limiting bodies and above-36 kV duty.
- Send the drawing, not a catalogue number. Bore, wall, end-cap interface and venting are all application-specific, and the body is machined to your link geometry.
A fuse body carries four duties at once. It insulates, so the arc cannot reach neighbouring phases. It contains, so the arc, hot gas and debris stay inside the barrel. It supports the element, so the fusible section stays where the design put it. And on expulsion and cutout designs it actively helps extinguish the arc by releasing gas into the bore. A body that fails any of those four takes the protection scheme with it.
That is why material selection cannot be reduced to a voltage number. A 24 kV drop-out cutout tube and a 24 kV current-limiting body may sit at the same voltage but face completely different thermal and pressure pulses. The cutout relies on gas generation and a long expulsion path. The current-limiting body has to survive a very high pre-arcing energy density in a short time, in a sealed barrel, and hold its bore geometry long enough for the element to part. Same voltage, different material, different bore, different venting.
Material map by voltage class and duty
| Voltage class | Fuse type | Body material | Liner / arc-facing surface |
|---|---|---|---|
| LV, up to 1 kV | Cartridge, HRC, cylindrical | G5 / G9 melamine tube, insulating paper, fish paper | Integral to the melamine wall, or a paper liner |
| MV, 1 to 12 kV | Current-limiting, transformer protection | G10 epoxy fiberglass, filament wound epoxy glass | Synthetic arc-quenching composite or a melamine liner |
| MV, 12 to 24 kV | Drop-out cutout, expulsion | Vulcanized fiber composite with epoxy fiberglass outer | Arc-extinguishing vulcanized liner, gas generating |
| MV to HV, 24 to 36 kV | Current-limiting, capacitor bank, striker | G10 / G11 epoxy glass, filament wound tube | Synthetic arc-quenching liner to drawing |
| HV, above 36 kV | Current-limiting, special HV | G11 high-temperature epoxy glass, ceramic epoxy glass, ceramic | Arc-quenching composite or ceramic bore |
| Non-arc structural | End caps, carriers, spacers, mechanical bodies | Vulcanized fiber, canvas epoxy, knurled and screwed fiber tube | None. Keep vulcanized fiber away from arc-facing surfaces |
Arc quenching: what the material is actually doing
When a fuse element parts under fault, an arc forms in the bore. The energy in that arc has to go somewhere. There are two production strategies, and they use different materials for the same reason.
Gas generation (expulsion and cutout designs)
A liner that releases gas when it meets the arc generates a high-pressure gas column inside the barrel. That column drives the arc along the bore and out of the open end, where it is stretched, cooled and extinguished. The classic material for this is a vulcanized fiber liner, which decomposes under arc heat and produces the gas. The outer wall has to hold the pressure while the liner does the work, which is why cutout tubes are usually a composite: an arc-extinguishing vulcanized liner wrapped in filament wound or epoxy fiberglass. Tensile strength on those wound outers runs around 280 MPa axial and up to 600 MPa circumferential, with arc resistance in the 150 to 180 second class and thermal stability to 180 °C (Class H).
Ablation and splitting (current-limiting designs)
In a current-limiting fuse the element parts into many short arcs inside a sealed, filled barrel. The arc energy is absorbed by the filler and by the bore surface, and the material has to resist that without losing its geometry. This is where a synthetic arc-quenching composite or a ceramic-filled epoxy bore earns its place. The body must also hold its dimensions through the thermal pulse, because a bore that swells closes the path the filler needs.
Bore geometry and venting
Bore diameter sets the arc energy density. Venting determines where the gas goes. Both are part of the fuse design, not free choices at the tube factory. Send us the bore, the venting arrangement and the breaking capacity you are designing to, and we machine the body to suit rather than supplying a standard bore that happens to be close.
Specifications we hold
| Parameter | Range / value |
|---|---|
| Voltage coverage | 1 kV to 36 kV production, above 36 kV on drawing |
| Body materials | Vulcanized fiber, vulcanized fiber composite with epoxy fiberglass, G5 / G9 melamine, G10 / G11 epoxy glass, filament wound epoxy glass, canvas epoxy, ceramic epoxy glass, synthetic arc-quenching composite |
| Inner diameter | From ~5 mm upward, to drawing |
| Outer diameter | Up to ~300 mm |
| Length | Up to ~2000 mm |
| Wall and concentricity | To drawing; thin-wall sections typically within ±0.05 mm on ID and OD |
| Typical cutout tube sections | 100 A: 12.7 mm ID x 18.24 mm x 25.4 mm OD; 200 A: 16 mm ID x 24 mm x 30 mm OD |
| Winding angle | 50 to 90 degrees, tuned for hoop and axial strength |
| Insulation strength | Axial 3 to 6 kV/mm, radial 10 to 12 kV/mm |
| Water absorption | Less than 0.03% on wound glass composite |
| Thermal stability | Class H, 180 °C and above depending on system |
| Machining | ID and OD ground or turned, internal steps, chamfers, threading, knurling, slotting, punching, OEM print |
| Standards cited | IEC 60269-2, IEC 60282-1, ANSI C37.47, IEC 60893, RoHS, REACH |
Standards listed are the ones we build against and can cite in documentation. Confirm which standard governs your approval file and we will match the test and inspection plan to it.
Pick this, skip this
Talk to us when
- You are launching a new fuse link, cutout door tube or current-limiting body and the material is still open
- The tube is a composite with an arc-quenching liner and the interface between liner and outer wall matters
- The end caps, contacts or firing mechanism need a machined interface held to a drawing
- The vehicle is PV, EV or ESS and the duty includes 25-year outdoor exposure with thermal cycling
- The existing body is failing at heavy fault duty and you need to know whether it is the material, the bore or the venting
- You need to move a ceramic body to a non-ceramic composite for weight or cost without losing breaking capacity
- You need COA, FAI and batch traceability with the link approval file
You are on the wrong track when
- The drawing puts vulcanized fiber on an arc-facing surface. Change the material before tooling
- The body is specified by voltage class alone with no breaking capacity and no bore definition. That specification cannot be quoted correctly
- You are reusing a catalogue bore for a redesigned element. Bore and arc energy are coupled; changing one changes the other
- The requirement is a standard LV cartridge and a low-cost rolled or pultruded tube will do. Do not over-specify a wound composite
- The plan is to substitute material without re-running the type test. Arc-facing material changes invalidate the test
- No one has stated the venting or gas path. On expulsion designs that is half the extinguishing mechanism
What goes wrong in the field
Vulcanized fiber specified against the arc
The most common technical error we see. Fiber machines beautifully and takes threads and knurls, so it gets used as a body material everywhere, including arc-facing surfaces where it does not belong. It belongs on mechanical bodies, end caps, carriers and spacers. On the arc, use melamine, ceramic-filled epoxy glass or a synthetic arc-quenching composite.
Bore changed without re-testing
A bore change alters arc energy density and gas volume, which changes the clearing performance. A body that passed a type test at one bore is not the same product at another. If the design changes, the test has to follow, and we will say so rather than quietly ship a different bore.
Composite interface not controlled
On a cutout tube the liner and the wound outer are bonded. If the interface has voids or the bond is inconsistent, the pressure pulse finds it and delaminates the tube. We control the bond as a process step with in-process checks, not as an afterthought.
End-cap interface tolerance too loose
The cap seals on a shoulder, a thread or a press fit. If the interface is out of tolerance the seal leaks, moisture enters the bore, and the element behaviour drifts over years. This is the failure that shows up late and gets blamed on the element.
Outdoor duty without UV and moisture accounting
PV and cutout bodies sit outside for 25 years. UV exposure, thermal cycling and moisture uptake all act on the outer wall. We coat and finish for UV resistance on those programmes, and we state the water absorption figure rather than leaving it implicit.
Thermal expansion mismatched to the cap
The body and the end cap expand at different rates. Where the differential is large, the joint works loose over thermal cycles. Expansion coefficient belongs in the design review, and we will raise it if the pairing looks mismatched.
Related Engineering Guides
- → Fuse Tube Material Guide: Choosing by Voltage Class and Duty
- → High-Voltage vs Low-Voltage Fuse Tube: Where the Design Splits
- → Vulcanized Fiber and Arc Quenching: What It Does and Does Not Do
- → How to Specify a Custom Fuse Tube on a Drawing
- → PV Solar Fuse Tube: Designing for a 25-Year Life
- → EV Fuse Link vs Fuse Tube Selection
Components for this solution
Fuse Body Tube for Power Protection
The full fuse tube line, from LV cartridge bodies to MV and HV composite tubes.
Vulcanized Fiber Tube
The structural and non-arc-facing tube, machinable with threads, knurls and slots.
Vulcanized Fiber Composite Fiberglass Tube
Composite cutout and drop-out tube with an arc-extinguishing liner inside a wound wall.
Synthetic Arc-Quenching Fuse Tube
Gas-generating liner for expulsion, drop-out and cutout duty.
Current-Limiting Fuse Tube
Sealed bodies that hold bore geometry through a high pre-arcing energy pulse.
MV/HV Fuse Link Bodies to Drawing
Cylindrical bodies with end-cap interfaces machined to your spec.
Ceramic Epoxy Fiberglass Tube
Arc-facing and HV duty where a filled system is required.
Canvas Epoxy Fuse Tube
Canvas-based composite body for mechanical and end-cap applications.
Fuse Link Body: Small Diameter, Thin Wall
Narrow bores and thin walls for compact link geometries.
G9 / G5 Melamine Tubes
LV, HRC and AC fuse body material with inherent arc resistance.
Vulcanized Fiber Combination Fiberglass Tube
Combined build for cutout and expulsion fuse bodies.
Knurled and Screwed Vulcanized Fiber Tube
Threaded and knurled fiber components for end caps and mechanical interfaces.
Related solutions
Common questions
What material makes a MV or HV fuse body tube?
It depends on the voltage class and the duty. LV cartridge and HRC bodies use G5 or G9 melamine, insulating paper or fish paper. MV and HV current-limiting bodies use G10 or G11 epoxy fiberglass or a filament wound epoxy glass tube. Cutout and expulsion tubes are usually a vulcanized fiber composite with an arc-extinguishing liner inside an epoxy fiberglass outer wall.
Is vulcanized fiber suitable for arc-facing fuse applications?
No. For arc-facing surfaces use ceramic-filled epoxy glass, melamine or a synthetic arc-quenching composite. Vulcanized fiber is for non-arc-facing mechanical bodies, end caps, carriers and spacers. It machines well and takes threads and knurls, which is why it gets over-applied, and that is the error we most often correct at drawing review.
How does the tube actually extinguish the arc?
Two mechanisms, depending on the fuse type. In expulsion and cutout designs the liner decomposes under arc heat and generates gas at high pressure, driving the arc along the bore and out of the open end where it stretches and cools. In current-limiting designs the element parts into many short arcs inside a sealed filled barrel, and the bore surface plus the filler absorb the energy while the body holds its geometry.
What voltage range do you build to?
Production coverage is 1 kV to 36 kV, with above-36 kV bodies built to drawing using G11 high-temperature epoxy glass, ceramic epoxy glass or ceramic. Tell us the class and the working voltage, not just the nominal.
Can you machine the end-cap interface?
Yes. We bore and turn ID and OD, cut internal steps and chamfers, thread, knurl, slot and punch to your drawing, and we review feature depth, edge distance and remaining wall before quotation. The cap interface is verified against the print, not against a blanket tolerance.
What tolerance can you hold on thin-wall fuse bodies?
On thin-wall sections we typically hold ±0.05 mm on ID and OD. Capability is confirmed against your drawing rather than published as a blanket figure, because the achievable tolerance depends on the diameter, the wall and the length.
What bore should I specify?
The bore that your element design needs, not a catalogue bore. Bore diameter sets arc energy density and gas volume, and both are coupled to the clearing performance you are designing for. Send the bore, the venting arrangement and the breaking capacity, and we will tell you if the material and wall you have chosen can carry it.
Can I change the bore or material on an existing tested design?
Not without re-running the relevant type test. Arc-facing material changes and bore changes both alter the clearing behaviour, so a body that passed at one configuration does not carry the approval at another. Tell us the standard governing your file so we can match the test and inspection plan.
Which standards apply?
IEC 60269-2 for LV fuses, IEC 60282-1 for high-voltage current-limiting fuses, and ANSI C37.47 for distribution cutouts are the ones most often cited. Wound composite bodies also reference IEC 60893 for the laminate. Confirm which standard governs your approval file and we will align documentation to it.
Do you supply cutout tubes in the common 100 A and 200 A sections?
Yes. Typical sections are 12.7 mm ID with a 25.4 mm OD for the 100 A class and 16 mm ID with a 30 mm OD for the 200 A class, in section lengths from roughly 240 mm to 1200 mm, with an inner layer diameter set to the liner. Custom ID, OD and length are made to drawing.
Can you supply the body and the liner as one bonded assembly?
Yes, and on cutout tubes that is the normal supply form. The arc-extinguishing liner is wrapped in resin-impregnated fibre glass at an optimised winding angle to give the finished tube its tensile and anti-burst strength, with the liner bonded as an integral part of the wall.
How do you handle outdoor and PV duty?
PV and outdoor cutout bodies see UV, rain, thermal cycling and salt fog for decades. We apply UV-resistant insulating finishes, control water absorption on the wound composite, and state the thermal stability class. For 25-year-life programmes, tell us the environment and the expected cycle count.
Can you print or mark the tube?
Yes. OEM print, part numbers, ratings and identification marks are applied to the drawing. Tell us the print area and the ink compatibility requirement, especially on coated bodies.
Do you provide COA, FAI and traceability?
Yes. Every batch is traceable to the incoming material certificate. Material COA, first-article inspection per your plan, in-process dimensional checks at each station and final inspection reports are supplied on request. Dielectric strength and insulation resistance testing is available.
What do you need to quote a fuse body tube?
The governing standard, voltage class, breaking capacity you are designing to, body and liner materials, ID, OD, wall, length, bore and venting arrangement, the end-cap interface with tolerances and datum scheme, features such as slots, threads and holes, finish and marking, acceptance criteria, and prototype plus annual volume.