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An alternator for use in an automotive vehicle includes a circuit for detecting initiation of rotation of an engine. Upon detecting the initiation of rotation, excitation current supply to a field winding is started, and thereafter an alternator output is controlled by controlling the excitation cur

An alternator for use in an automotive vehicle includes a circuit for detecting initiation of rotation of an engine. Upon detecting the initiation of rotation, excitation current supply to a field winding is started, and thereafter an alternator output is controlled by controlling the excitation current. A resistor is connected to one phase winding of an armature to obtain a voltage indicating initiation of rotation during a period in which no excitation current is supplied to the field winding, and a capacitor is connected to another phase winding to raise the indicating voltage level. Since the indicating voltage induced by a small amount of residual magnetism is increased to a sufficient level by the capacitor, the initiation of rotation can be accurately detected.

대표청구항 ▼

1. An automotive alternator, comprising: a rotor having a plurality of field poles; a field winding for magnetizing the field poles; an armature for generating alternating voltage induced by a rotating field of the rotor, the armature including three-phase windings; a rectifier for rectifying

1. An automotive alternator, comprising: a rotor having a plurality of field poles; a field winding for magnetizing the field poles; an armature for generating alternating voltage induced by a rotating field of the rotor, the armature including three-phase windings; a rectifier for rectifying the alternating voltage into a direct current voltage, the rectifier including at least one negative-side diode; a voltage regulator including a resistor for detecting a low voltage induced in one of the three-phase windings by residual magnetism in the field poles, the resistor being connected to the one of the three-phase windings; and a capacitor connected between another one of the three-phase windings and a negative terminal of the rectifier, wherein the voltage regulator detects initiation of rotation of the rotor based on a voltage across the resistor thereby to start excitation current supply to the field winding, and thereafter controls the excitation current to control an output voltage of the alternator. 2. The automotive alternator as in claim 1, wherein: the voltage regulator determines that rotation of the rotor is initiated when the voltage across the resistor is higher than a predetermined level and a frequency of the voltage exceeds a predetermined frequency. 3. The automotive alternator as in claim 1, wherein: an impedance of the capacitor in a basic frequency region corresponding to an idling speed of an automotive engine is set to a level lower than a resistance of the resistor. 4. The automotive alternator as in claim 2, wherein: an impedance of the capacitor in a basic frequency region corresponding to an idling speed of an automotive engine is set to a level lower than a resistance of the resistor. 5. The automotive alternator as in claim 1, wherein: the voltage regulator is composed of Zener diodes; and an impedance of the capacitor is set to such a level that the voltage appearing across the resistor at a maximum rotational speed of the rotor under a situation where no exciting current is supplied to the field winding becomes lower than a Zener voltage of the Zener diodes.