Types of Fuses: NH, HRC, Cut-Out, PV and Fuse-Switch Forms

Fuse types are decided by the body and the contact system, not by the current rating. A 100 A NH knife-blade link, a cylindrical HRC cartridge, an LV service cut-out and a PV fuse can share the same ampere figure and still not fit each other's holder. This guide covers the forms YOMIN actually builds, what each is for, and the label checks that decide whether a substitute will work.

Fuse type is a mechanical question first

Every fuse has to do two things: carry the load current without overheating, and interrupt a fault without letting the arc restrike. The second job is what shapes the product. A body designed to clamp between blade contacts in a base cannot be swapped for a screw-in or a bolt-in form, whatever the label says about amperes.

That is why the practical order of selection is: holder or base first, voltage and duty second, current rating third, breaking capacity fourth. Buyers who start from the ampere figure usually end up with a part that protects correctly on paper and does not physically install.

The fuse families side by side

Catalogues use different words for the same family, so the contact geometry is the reliable identifier. Two parts that look alike in a photograph are often separated by the size code alone.

NH knife-blade fuses

NH links are the workhorse of industrial low-voltage distribution. The two blade contacts slide into spring clips in a base, so the link is changed without touching a bolt and the base stays wired. Sizes are standardised by body width, which is what makes a 160 A NH00 link from one supplier fit another supplier's base.

YOMIN's NH00 knife-blade link (ym-0378) is a 160 A, three-pole copper link in a polyester body, intended for overload and short-circuit protection. The NH1 PV DC version (ym-0066) covers 80 A, 125 A and 250 A at 48 V DC for solar distribution boxes, keeping the same blade geometry with a DC-rated element.

Two ordering details cause most returns: the size code, because NH00 and NH1 are not interchangeable even at the same current, and whether the element is a general-purpose or a motor-duty type. Ask for both in writing.

HRC cartridge fuses

The HRC cartridge is a sealed ceramic tube filled with quartz sand, with blade contacts bolted to a busbar or held in a clip. Sealing the arc inside the tube is what gives this form its high breaking capacity in a small volume, and why it survives in motor circuits and feeders where a miniature device would be undersized.

The HRC fuse guide covers element classes and time-current behaviour in detail. For type selection the point to keep is that the cartridge is a bolt-in or clip-in part: the holder, not the fuse, determines the mounting.

Service cut-outs are still the standard LV form

In much of Asia, Africa and the Middle East the service cut-out remains the default protection at the supply point: a bakelite base, a fuse carrier and two terminals. It is inexpensive, the occupant can replace the fuse, and installation teams already know it.

The range starts at small single-phase ratings. ym-0174 is a 32 A, 1P+N single-phase cut-out fuse with a high breaking capacity, and continues to the 1501 house service cut-out (ym-0746) at 60/80 A and 500 V in the same 1P+N pattern. For single-pole work, ym-0135 is a 500 V bakelite cut-out built for high-breaking service.

The failure mode to design out is contact heating. A carrier that is opened repeatedly under load will char at the contacts, so where switching is frequent a fuse-switch is the better answer.

PV and DC fuses

Direct current does not pass through zero, so an arc drawn on a DC circuit sustains itself until the gap is long enough or the current collapses. A fuse rated for AC service only, used on a string, may interrupt once and weld on the second event.

YOMIN builds the PV fuse series with a replaceable holder (ym-0321) and the FG series box form with knife-shape contacts (ym-0330), both for low-voltage PV work, alongside the 48 V DC NH1 link above. The selection rule is the DC system voltage, not the AC equivalent: a 1000 V DC string needs a fuse marked for that DC voltage.

String fuses also need the correct current ratio to the module short-circuit current, and that calculation belongs to the array design rather than to the fuse catalogue.

Fuse-switch disconnectors

Where maintenance staff must see an open gap before touching a circuit, a fuse-switch disconnector does isolation and protection in one body. The knife contacts open visibly, the fuse carrier sits behind a touch-safe cover, and the assembly replaces a separate isolator plus a fuse base.

The PB series is built this way: fp-1063 at 250 A and fp-1064 at 400 A, both with anti-accidental-touch knife switches in flame-retardant PC with pure copper contacts, carrying CE and RoHS marking. The BP32 negative-pole isolating switches in the same catalogue extend the pattern to 630 A for DC and battery work.

Reading the label: five checks before substituting

The first and last checks are the ones buyers skip. Voltage is usually printed on the body; the size code often is not, and it is the one that decides fit.

Choosing between the forms

If the base is already installed, start from the size code and buy the link that fits it. If the panel is new, choose by duty: cut-outs at service entrances and small boards, NH links for industrial LV distribution and PV DC, HRC cartridges where breaking capacity is tight, and fuse-switches wherever visible isolation is required.

The fuse and protection selection guide walks through the sizing steps, and the fuse versus circuit breaker comparison covers the decision to use a fuse at all. Holders, bases and the full range are listed under fuses and protection.

Frequently asked questions

Is an NH fuse the same as an HRC fuse?

Not exactly. HRC describes breaking performance, meaning a high rupturing capacity. NH is a body and contact standard with defined sizes. An NH link is an HRC fuse, but many HRC cartridge fuses are not NH, so the size code is what decides interchangeability.

Can I replace a 250 A link with a 300 A one?

Only if the base, the cable and the upstream protection are all rated for 300 A. The fuse is meant to be the weakest point in the circuit; raising it without checking the cable moves the weak point into the wiring.

Do I need a DC-rated fuse for a solar string?

Yes. A fuse rated only for AC may fail to extinguish a DC arc. The rating must state the DC voltage of the string, and the current must be matched to the module short-circuit current.

What is the difference between a cut-out and a fuse-switch?

A cut-out is a low-cost carrier for a replaceable fuse with no load-breaking mechanism. A fuse-switch adds a visible knife gap and a touch-safe cover, so it can be opened under load and used as an isolator.