Proposal of Electromagnetic Clutch Structure to Suppress Surge Voltage

A new structure for a vehicular electromagnetic (EM) clutch is proposed here that suppresses the surge voltage generated by turning off the ignition switch of a vehicle. Through the theoretical consideration of the EM field, it is found that a larger eddy current in the EM clutch would be able to suppress the surge voltage because it causes a small time change in the magnetic flux passing through the coil. Therefore, the proposed structure has a metal layer with low resistivity surrounding the clutch coil and located between the coil and the coil housing. Numerical calculation of the EM field and electrical circuit, which expresses the measured time-series surge voltage well, shows the suppression effect of the surge voltage with the proposed structure. Therefore, the structure is verified to be useful for suppressing the surge voltage.