Torque and back-emf in hybrid excited claw pole generator

Abstract

Purpose The paper aims to present the hybrid excited claw pole generator design, simulation and experimental results. The prototype has claw poles on two rotor sections, between which an excitation coil is located. The innovation of this machine is permanent magnets location on claws of one part of the rotor. The paper presents construction of the machine and analysis of the current in the excitation control coil influence on the electromagnetic torque, cogging torque and back-emf values. Presented studies enabled the determination of the torque and the back-emf for both: the strengthening and the weakening of magnetic field. Design/methodology/approach In the study, finite element analysis was used to perform simulation research. Then, based on the simulation studies, an experimental model was built. The paper also presents selected experimental results. Findings Achieved results show that the proposed machine topology allows to eliminate the disadvantages mentioned in paper, i.e. necessary to introduce special areas inside the machine to limit magnetic flux leakage or its complicated construction. Research limitations/implications The obtained cogging torque values and back-emf pulsation are still relatively high. In the near future, some of known techniques for reducing these pulsations can be applied, including the use of magnetic wedges, changing shapes of rotor’s poles and/or skewing of permanent magnets. Practical implications The proposed solution can be used in wind turbines as a generator. Originality/value The paper presents an original design of a new construction of a hybrid-excited claw pole machine and also an excitation current influence on cogging torque and back-emf values.

Modern Hybrid Excited Electric Machines

“…One of the innovative solutions is the use of hybrid excitation in claw pole machines by placing permanent magnets on or inside the claws. A construction of a hybrid excited claw machine with permanent magnets placed in milled areas on one [56] or both parts [57] of the rotor was proposed. Figure 16 shows these structures.…”

“…As a result of the work, it was possible to develop a technical solution that made it possible to self-excite the machine without the use of an additional DC source. In the first solution [56], self-excitation took place at the rotational speed equal to 1300 rpm, while in the second solution [57]-at 850 rpm. This feature can be used in a home wind turbine-in the absence of wind, thanks to the use of one diode, the generator regulator would not get energy from the batteries, while when the wind of sufficient strength appears, the generator would be self-excited, and consequently the energy would be generated for the storage system.…”

“…Figure16. Visualization of a claw pole machine: (a) With permanent magnets on one part of the rotor[56]; (b) With permanent magnets on both parts of the rotor[57].…”

The Design and Optimization of a Novel Hybrid Excitation Generator for Vehicles

“…Therefore, it not only has the good adjustment characteristic of a silicon rectifier generator but also has the advantages of high-power density, high efficiency and high reliability of a permanent magnet generator. It is suitable for operating conditions with variable speeds and loads [5][6][7][8].…”