The NH system is classified among plug-in fuse systems and is composed of:
- fuse-base (possibly including terminal covers and phase barriers)
- fuse-link with blade contact
- fuse-link replacement device (LV HRC fuse puller)
Since the design of this system cannot guarantee non-interchangeability of rated current it must be handled by a qualified professional. Type aM NH fuse-links are partial-range breaking capacity fuse-links, used to protect motor circuits as they are strongly current-limiting and have low power losses. They interrupt currents from 6.3 times In up to their maximum breaking capacity and are therefore suited for short-circuit protection only. They must be associated with other switchgear for protection against overloads. These fuse-links can have a rated current equal to the motor's nominal current.