Breaking capacity where it matters
NH fuse systems are chosen for high prospective short-circuit currents, visible isolation and predictable current limitation. Where a circuit breaker would need a larger frame to reach the same breaking capacity, an NH link achieves it in a compact footprint.
Selection by application, not only by current
- gG (general purpose): cable and line protection in distribution circuits.
- aM (motor protection): short-circuit protection for motor feeders, used together with an overload relay.
- Semiconductor and DC applications: specialist links on request.
Bases and carriers built for the link
Porcelain bases are dimensioned for the thermal and mechanical load of the matching link size, with contact blades that keep the contact pressure over the service life. Three-pole bases are available for panel mounting and for direct mounting on the busbar system.
Documented coordination
Fuse links are tested to IEC 60269. Where a fuse is combined with a switch disconnector, the assembly is selected as a unit so the making and breaking capacity of the switch matches the link.
1. Determine the required breaking capacity
Start from the prospective short-circuit current at the point of installation. The fuse rating must exceed it; NH systems are normally chosen where the fault level is high and space is limited.
2. Choose the characteristic
- gG for cable and line protection — the link protects the cable against overload and short circuit.
- aM for motor circuits — the link covers short circuit only and an overload relay covers the overload.
3. Size the link to the cable, not to the load alone
The rated current of the link must not exceed the current-carrying capacity of the cable it protects, after correction for ambient temperature and grouping.
4. Select the base and carrier
Match the base size to the link size (NH000 to NH4, NT00 to NT4), choose single-pole or three-pole, and decide between panel mounting and direct busbar mounting. Add a cover where the base is accessible.
5. Add monitoring if the process cannot stop
Fuse monitoring and signal switches report a blown fuse to the control system, which matters in unattended installations and in processes where a single-phase loss would damage motors.
What to send for a quotation
- Link size and rated current, characteristic (gG or aM)
- Rated voltage and the prospective short-circuit current
- Base type: single-pole or three-pole, panel or busbar mounting
- Whether monitoring, signal switches or covers are needed
- Quantity per size and delivery destination
