Permeance coefficient (PC) value of magnet

• Magnets with higher PC values have either same diameter with longer length or same length with smaller diameter.
• Magnets with higher PC values have better self demagnetization characteristics and hence lower aging loss.

Density of magnet

• To achieve higher density, magnets are pressed with higher tonnage. This causes additional powder fracturing which creates fresh surfaces.
• Exposed fresh surfaces lead to higher aging loss.

Saturation of magnet

• Insufficient saturation of the magnet results in
  • Reduced squareness of hysteresis loop
  • Lower Hci

• Reduced squareness and lower Hci leads to higher aging loss.