The NH system is assigned to the plug-in fuse systems and is made up of the following: fuse base (possibly with connection covers and phase cover), fuse inserts with contact blades, device for replacing the fuse inserts (low-voltage plug-in handle), maintenance and repair must be carried out by qualified personnel. NH fuse inserts of operating class aM are partial range fuses and protect electrical devices from destruction in the event of impermissibly high short circuits due to their strong current limitation and low thermal conductivity values. They switch off currents that are greater than 6.3 x IN up to the maximum breaking capacity. NH fuse inserts aM are preferably used to protect systems and switching devices in motor circuits. When assigning the NH inserts, the nominal fuse current can be selected to be equal to the nominal motor current. VDE 0636 Part 201, IEC 60269-1 and -2.