Patent ID: 7642690

Claim:
A tandem alternator comprising: a rotary shaft; a first and a second field which are arranged in tandem on the rotary shaft, the first field including a first lundell-type field core fitted on the rotary shaft and a first field winding wound around the first field core, the second field including a second lundell-type field core fitted on the rotary shaft and a second field winding wound around the second field core; a first and a second armature which are arranged in tandem in an axial direction of the rotary shaft, the first armature being provided on an outer periphery of the first field to constitute, together with the first field, a first electric power generation unit, the second armature being provided on an outer periphery of the second field to constitute, together with the second field, a second electric power generation unit; a housing rotatably supporting the rotary shaft and accommodating therein both the first and second electric power generation units, the housing having a first and a second end face that are apart from each other in an axial direction of the rotary shaft with the first and second electric power generation units intervening therebetween, the first end face being closer to the first electric power generation unit than the second electric power generation unit, the second end face being closer to the second electric power generation unit than the first electric power generation unit; a slip ring-brush mechanism provided around an end portion of the rotary shaft, which is closer to the second end face than the first end face of the housing, to pass a first and a second field current respectively to the first and second field windings; a first and a second rectifier which are respectively fixed to the first and second end faces of the housing and work to respectively rectify AC powers output from the first and second armatures into DC powers; a controller electrically connected between the first rectifier and the slip ring-brush mechanism to control, at least, supply of the first field current to the first field winding, the controller controlling the supply of the first field current to have an ON mode, in which the first field current flows from the first rectifier to the first field winding via the controller and the slip ring-brush mechanism, and an OFF mode in which the first field current is interrupted, the controller being configured to form, when the supply of the first field current is in the OFF mode, a freewheeling circuit to discharge energy stored in the first field winding, the controller being fixed to the second end face of the housing to minimize a distance from the controller to the slip ring-brush mechanism, thereby minimizing resistance loss of the freewheeling circuit; and an electric wire that electrically connects the first rectifier to the controller, wherein the electric wire is arranged outside both the first and second armatures in the radial direction of the rotary shaft.