Industrial fuses provide reliable overcurrent protection for motors, transformers, and power distribution systems. This guide covers fuse selection for common industrial applications.

Motor Protection Fuse Selection

For motor protection, use gG (general purpose) fuses with separate overload relays. The fuse provides short-circuit protection while the overload relay handles motor overload conditions.

Sizing Guidelines:

  • Fuse rating = 1.5-2.5 x motor full-load current
  • Higher ratios for high-inertia loads
  • Verify fuse can handle motor starting current
  • Use aM fuses only with proper overload relays

NH Fuse Types

NH fuses are standardized per DIN 43620 and IEC 60269-1:

  • NH000: 2-100A, compact size
  • NH00: 2-160A, common for control circuits
  • NH1: 2-250A, medium power applications
  • NH2: 2-400A, large motors and distribution
  • NH3: 2-630A, high power applications

Coordination Requirements

Proper fuse coordination ensures selective protection:

  • Downstream fuse operates first
  • Maintain 2:1 current ratio between levels
  • Time-current curves should not overlap
  • Consider fault current at each location