Basic mechanism and working principle of brushless three-phase alternator

Basic structure

The brushless three-phase alternator structure is basically the same as the brushed three-phase alternator, and its components are exploded as shown in Figure 3-15 . Show. It differs from the brushed three-phase alternator structure in that it replaces the collector ring with an AC exciter and a rotary rectifier. The AC exciter is a three-phase alternating current generator that senses three-phase alternating current with the pole core and the pole winding on the stator and the armature on the rotor. See Figure 3-40 for the structure of AC exciter and rotary rectifier for brushless three-phase generators . The AC exciter stator includes a stator core and a stator winding. The stator core is the main part of the magnetic circuit of the AC exciter, which is assembled by stacking stator cores. When the direct current flows through the stator winding, the stator core establishes the main magnetic field of the AC exciter.

The AC excitation electromechanical armature includes an armature core and an armature winding, and the armature core is also a main part of the magnetic circuit of the AC exciter, and is formed by stacking armature core punching sheets. The armature winding is a part of the AC exciter that emits three-phase alternating current, which is rectified into a direct current by a rotary rectifier to supply an excitation current to the generator rotor winding.

The rotary rectifier is assembled into a three-phase full-wave rectifier by six rotating rectifying elements, or is assembled into a three-phase half-wave rectifier by three rotating rectifying elements, which are fixed on the rotating shaft of the brushless generator for emitting three of the armature windings. phase AC voltage to DC input rotor winding wire and dried.

2. Working principle

The principle circuit of the brushless three-phase alternator is shown in Figure 3-16. A generator driven by the engine rotation close to the rated speed, the rotor pole double relying residual magnetic field and the AC exciter stator core pole cores, a stator core fitted in the groove in the secondary winding (main winding or tap) induces a voltage, and by AVR After the rectification link is rectified, the stator winding of the AC exciter is input, and the magnetic field of the AC exciter is established. The AC excitation electromechanical three-phase winding induces a three-phase AC voltage. The voltage is rectified into a DC voltage by a rotary rectifier, and the rotor pole winding is input to establish a main magnetic field of the generator, so that the generator stator winding induces a three-phase voltage and outputs three-phase electric energy. . Adjust the potentiometer in the AVR to set the terminal voltage to the rated value. At load time , the AVR automatically throttles the generator excitation current to maintain the generator voltage constant.