Bourns, Inc. Resettable Fuses MF-R025

PTC RESET FUSE 60V 250MA RADIAL

MF-R Series, Radial Leaded PTC Resettable Fuses, 60 V Voltage Rating, 40 A Current Rating, Multifuse products are made from a conductive plastic formed into thin sheets with electrodes attached to either side. The conductive plastic is manufactured from a non-conductive crystalline polymer and a highly conductive carbon black. The electrodes ensure even distribution of power through the device and provide a surface for leads to be attached. The conductive carbon black filler material is dispersed in the polymer. When the polymer is at room temperature, there are numerous carbon chains forming conductive paths through the material. Under a fault condition, I 2 R heating causes the plastic material's temperature to rise, resulting in a phase transformation of the polymer matrix to an amorphous stricture. This is accompanied with a small expansion. As the conductive particles move apart, most of them no longer conduct current and the resistance of the device increases sharply. The device will remain in this condition until the fault is cleared, allowing the carbon chains to reform as the polymer re-crystallizes. The resistance quickly returns to its original value. While fuses work well only once, replacement is not an option in many applications due to inconvenience, warranty cost or damaged reputations. Applications for resettable devices include computers and PDAs, motors, audio equipment, test and measurement equipment, security and fire alarms, medical, POS equipment, industrial controls, automotive and marine electronics, and battery-operated toys. Maximum Current: 40-100 amps. Manufacturer's literature available upon request. Kinked lead option is available for board standoff. Contact Allied for details.