A Consequent-Pole Hybrid Exciter for Synchronous Generators

Abstract

In low-to-medium power generating sets, a selfpowered brushless excitation system is typically employed. This solution is cost-effective, simple and compact, but it suffers from an unreliable voltage build-up at start-up, a slow dynamic response and a relatively low efficiency for the exciter. The push towards more effective, reliable and efficient products has recently led to consider excitation systems equipped with permanent magnet exciters and controlled rotating converters, but their diffusion is limited by their higher complexity and cost. This paper investigates the utilization of a hybrid excitation for the exciter, aiming to join the benefits of field windings and permanent magnets. As a case study, this concept is applied to a mid-size industrial generating set. After a preliminary analysis, a consequent-pole layout with surface-mounted bonded magnets is selected as the most effective solution in an industrial perspective, since it permits to maximize the benefits while minimizing the required modifications in the system design. Theoretical considerations, numerical analysis and experimental validation are reported to show that the hybrid excitation concept can actually lead to a significant reduction of the exciter field losses as well as to other appreciable side benefits with a very limited impact on the present design of the generating set.

Exciterless Wound-Field Medium-Power Synchronous Machines: Their History and Future

“…Whereas the 'brushless' AC exciter replaces the commutator/slip-ring arrangement with a shaft mounted diode rectifier, this provides a maintenance free solution whilst still leveraging the prime mover power, thereby minimizing converter requirements of the control system. These advantages make it the dominant choice for medium-plus power machines [3], [4]. Both these solutions are still in common use today despite a number of exciterless topologies having been proposed.…”

An Active Control Excitation Method of Three-Stage Brushless Synchronous Starter/Generator in Electric Starting Mode for MEA

“…In [33], a SVPWM control inverter circuit is proposed to study the excitation current characteristics of input exciter under different SVPWM modulation; SVPWM control has the advantages of less current harmonics, less torque ripple and higher DC voltage utilization. In [34], it is investigated a different solution consisting in using an exciter featuring a hybrid excitation, equipped with both PMs and field winding. In addition, considering the additional copper and core loss of the exciter, many various models have been established to optimize the design of the auxiliary exciter, such as a transfer function model in [35], an equivalent circuit model in [36], and a dynamic model in [37].…”

PM Halbach Arrays in Motors: Loss Reduction and Performance Improvements

“…In study 'B', the magnets will be segmented along the axial direction. Then, in study 'C', the PMs will be firstly changed from arcshaped to bricks [11], then the angular span Spm will be investigated. Study 'D' will modify the PM tips that is near the airgap.…”