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electromagnetic clutch[i¦lek·trō·mag′ned·ik ′kləch]
an electromagnetic device for the connection and disconnection of two coaxial shafts or of a shaft and a loosely fitting part, such as a gear or a pulley. Electromagnetic clutches provide for remote control and easy automation. They are used in, for example, metalcutting machine tools and diesel locomotives.
The following types of electromagnetic clutches are distinguished: electromagnetically activated friction clutches, electro-magnetically activated positive clutches, magnetic fluid and powder clutches, hysteresis clutches, and eddy-current clutches (seeCOUPLING).
Electromagnetically activated friction clutches are usually disk clutches; less often, they may be cone clutches. Electromagnetically activated positive clutches have small teeth that are usually located on the mating faces. In magnetic fluid and powder clutches, a space in the magnetic coupling system between the driving and driven clutch members is filled with a powder or liquid mixture that contains a ferromagnetic powder. Under the influence of a magnetic field, the viscosity of the mixture increases, thereby coupling the clutch members.