Patent ID: 8689950

Claim:
An electromagnetic type retarder comprising a main portion consisting of a stator having a plurality of magnetic coils arranged along a circle and spaced apart from one another, and of a steel rotor surrounding the stator and rotated according to the rotation of a tire; a driving device for the main portion to be controlled by an operation signal; and an output terminal for an additional device; the magnetic coils consisting of three-phase connections of A phase, B phase and C phase, each of the magnetic coils being connected with a capacitor so as to form a resonance circuit, respectively, the driving device having transistors connected in series to each of the three-phase connections and controlled so as to be opened and closed by the operation signal, wherein the revolution speed of a rotary magnetic field generated by three-phase AC voltage induced in the magnetic coils forming the resonance circuits by the rotation of the steel rotor is set smaller than the revolution speed of the steel rotor, and wherein the three-phase AC voltage is rectified to a DC voltage and applied to an input terminal of the additional device.