A Novel DC-Coil-Free Hybrid-Excited Machine with Consequent-Pole PM Rotor

Abstract

This paper proposes a new DC coil free hybrid excited machine concept, which has no external field windings. The technical novelty is the integration of field windings and armature windings. DC bias current is injected into the excitation and the field windings in the traditional hybrid excited machine are eliminated. Compared with traditional hybrid-excited machines with additional field windings, the proposed machine can realize a higher slot utilization ratio, hence achieve a higher torque density and a wider flux adjusting range. Another advantage of the proposed machine is that the voltage drop associated with flux regulation is small due to the small DC resistance, and the torque generating capability at the flux regulating region can be improved accordingly. The rotor is specifically designed with magnet-iron sequences and a consequent-pole, in which the permanent magnet and iron pole are alternatively employed. A bi-directional flux modulating effect can be achieved, which can contribute to the magnetic coupling in the air-gap. Analytical derivation is used to describe the operating principle, and the proposed machine was optimally designed using the Tabu search algorithm. A prototype was made, and its performances investigated through experimental tests.

Optimization Design and Performance Evaluation of a Hybrid Excitation Claw Pole Machine

“…B m is the maximum flux density. The three design objectives (i.e., torque, torque ripple, loss) are closely influenced by the MMF and air gap permeance [12], and the relationship between them and w PM , w not , w st , d PM , d ry , d st , g main can be obtained from [12]. The PM MMF, field excitation equivalent MMF and air-gap permeance are determined by the seven dimension parameters (i.e., w PM , w not , w st , d PM , d ry , d st , g main ).…”

“…Moreover, conventional CPM has two major drawbacks: clawto-claw flux leakage leads to low efficiency and the use of a slip-ring system leads to low reliability [7][8][9][10][11]. A permanent magnet claw pole machine (PM-CPM) can address the slip-ring system problem and the permanent magnet (PM) excitation method can reduce the volume of the machine and improve the power density and efficiency [12]. However, it is difficult to regulate voltage and is easily affected by temperature.…”

“…The air gap field is mainly produced by PMs and the role of the field current is to adjust the air gap field. HE-CPM can achieve a wide constant power speed range and higher efficiency at the flux weakening region [12].…”

Flux-Modulated Permanent Magnet Machines: Challenges and Opportunities

“…Induction machines used to be the leading choices for traction applications because of the robust structure, low cost, and simple control technique. However, with the development of high energy density permanent magnet (PM) materials, PM machines are gradually taking the leading position, because PM machines can achieve higher torque density and higher efficiency [7,8]. The PMs can be surface mounted on the rotor [9] or inserted into the rotor [10], and they can be magnetized in a special pattern referred to as Halbach array [11] to make the air-gap flux more sinusoidal and increase torque and efficiency accordingly.…”