Abstract
The magnetic properties of the claw pole have a direct effect on the output power of a generator. Many methods can be used to measure these magnetic properties, each with its own advantages, but an important shortcoming is that all are destructive. In this study, a new non-destructive method to measure the magnetic properties of claw pole was proposed and a corresponding testing set-up was designed. A finite-element model was constructed to simulate the measurement process. Results proved that the measured magnetization-like curves had good agreement with the trend of the input magnetic curves and the effect of the positioning error in the measuring process could be neglected. To further validate the new method, seven types of claw poles of different materials subjected to different heat-treatment processes were forged and tested by both the new method and the conventional ring-sample method. Compared with the latter, the new method showed better consistency, relatively higher accuracy, and much stronger stability of measurement results; however, its sensitivity needs to be improved. The effects of material compositions and heat-treatment parameters on the magnetic properties of the claw pole were briefly analyzed.
Highlights
The claw pole is a necessary component of a synchronous generator with direct-current (DC) excitation, which is commonly used in the automobile industry because of its low cost and ease of regulation [1]
Claw poles are mainly manufactured by hot forging: common forging schemes include closed-die forging [2], casting–forging [3], single forging with a spring-controlled die [4], and radial forging with forward extrusion [5]
The effect of precipitate element addition on the magnetic properties of the magnetostrictive Fe83Ga17 alloy was studied with ring samples: the results showed that the coercivity significantly increased with the addition of such elements [9]
Summary
The claw pole is a necessary component of a synchronous generator with direct-current (DC) excitation, which is commonly used in the automobile industry because of its low cost and ease of regulation [1]. 3.2 Simulation Results To analyze the measurement process in detail, specific magnetization curves, which were measured using the ring-sample method, of two claw poles made by different manufacturing processes (shown in Figure 5) were imported into the constructed FE model to simulate the static magnetic field. The magnetic flux density through the cross-section of the inner boss of the claw pole was quite uniform and the absolute value was larger than that of other zones This proved that the use of Eq (1) for the calculation of magnetic induction intensity was reasonable.
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