Klixon® 3MP Self Hold

Manufacturer: Klixon®

Motor Protector

Recent history has seen a growing demand for a non-self resetting motor protection device to ensure a high level of safety. Sensata Technologies has developed the self hold motor protector for both 120 & 250 Vac applications in a wide current range. The heart of the 3MP self hold consists of the pre-set Klixon® snap action bimetallic disc welded into a metal housing with integrated terminal. The housing is covered by the plate on which a heater can be welded to increase the current sensitivity of the device. A PTC pill is mounted on top of the metal housing by a clip to meet the requirements for self hold.

The combination of a variety of standard terminal configurations and carefully selected materials provides easy handling and mounting. Customized terminal configurations are available on request. Wires including connectors can be automatically attached to the standard crimp terminals. Sensata Technologies supplies a range of standard leads configurations; customized solutions are available on request. In construction where the 3MP self hold device is contacting conductive parts of the motor assembly, Sensata Technologies can deliver the self hold devices with a Mylar ™ insulation sleeve. Customized coding and coloring is an option on request. The operating principle of the 3MP self hold is both simple and effective. The protector is actuated by current passing through it and by the heat received from surrounding parts.
The electrical circuit is interrupted when the disc reaches its pre-set open temperature. Due to the heat supply from the PTC pill, the bimetal disc does not cool down below the close temperature. The contacts will remain open untill the appliance switched off by the user, assuring a higher level of safety. When switched off the device cools down to a safe temperature again and the contacts will automatically reset. The bimetal disc provides excellent thermal and current sensitivity in overload situation. Under locked rotor conditions the integrated heater in combination with the bimetal disc provide very accurate trip times for maximum protection. Applications The 3MP self hold is used in domestic and industrial electric motors for washers, vacuum cleaners, chain saws, trimmers, lawn mowers and pumps in the 120 and 250 Vac applications.


  • Provides higher level of safety for appliances having free access to rotating parts
  • Minimizes the total cost of the motor protection function
  • Guarantees to pass the UL 18 days locked rotor test in combination with high currents
  • Provides mounting flexibility.
  • Assures maximum protection under locked rotor conditions
Application domestic and industrial electric motors