Chapter3-AC machine Fundamentals《Electric Machinery 电机学（英汉双语）》英文课件.ppt

Chapter 3 AC Machine Fundamentals ? Operation Principles of the Three- Phase Synchronous Generator ? AC Windings ? Induced EMF of AC Winding ? Operation Principles of the Three- Phase Induction Motor ? MMF of AC Brief Content Operation Principles of the Three- Phase Synchronous Generator A simplified two-pole d three-phase synchronous generator is shown. The field winding on the rotor is excited by a DC voltage. The stator winding is a set of balanced three-phase winding with an axis of each phase displaced by 120 ?, and plete winding of each phase is represented by a single coil, there are six coil ends , which are A and X, B and Y, C and Z . These coil sides are placed in slots on the stator. ? the radial distribution of the air-gap flux density B is shown. As the rotor rotate s , the flux waveform sweeps by the six coil sides. The resulting coil voltage is a time function which has the same waveform as the spatial distribution B . And there are six sinusoidal waveforms of emf are induced in the six coil sides respectively, they have the same magnitude . ?t he space phase differences between two adjacent conductors are 60 ?, therefore, the induced emf time phase differences between two adjacent conductors are 60 ?, and the induced emf phasor -diagram of the six coil sides is shown. ? The set of three-phase stator windings can be connected to wye (Y) connection or delta ( ?) connection. A XA AXEEEE ????2??? B BYEE ??2? C CZEE ??2?? In a three-phase synchronous generator, a DC current is applied to a rotor winding, which will produce a rotor ic field. When the rotor is driven by a prime mover at a constant speed, there will be a rotating ic field in the machine. This rotating ic field induces a set of three-phase voltages within the stator windings of the generator. If the three-phase windings of the generator are connected to those three identical loads; there will be thre