Search

Depending on the stator lamination manufacturing processes (e.g., punching, laser cutting, clamping, welding, interlocking, and bonding), the motor’s magnetic performance parameters, such as cogging torque, hysteresis torque, and iron losses, can vary significantly. In sub-fractional horsepower (SFHP) permanent magnet motors, the manufacturing influence is typically even more severe because, due to their small dimensions, practically, the whole stator material is likely to be affected. This article analyzes the magnetic performance parameters cogging torque, hysteresis torque, and iron losses of three different stator lamination stacks (i.e., M250-35A punched with interlocking, M250-35A laser cut with bonding, and NO10 laser cut with bonding) of an SFHP single-phase brushless permanent magnet motor often found in automotive fan applications. A rheometer is used for extremely accurate torque measurements in the sub-millinewton meter range, and electron backscatter diffraction measurements are performed to visualize changes in the grain morphology and crystal orientation. The findings reveal that the punched stator with interlocking is affected the most by the manufacturing process, showing the lowest cogging torque yet the highest average hysteresis torque and thus up to 40% higher iron losses. The results presented in this article allow for both making basic stator lamination design choices and translating the iron losses, as well as the hysteresis torque and cogging torque waveforms, of a laser cut and bonded prototype into those of its punched and interlocked mass-produced counterpart. [ABSTRACT FROM AUTHOR]

Cogging torque reduction measures are hardly applied to low-cost sub-fractional hp brushless direct current (BLDC) motors, because the additional fabrication operations involved typically increase both the manufacturing complexity and cost significantly. By proposing an innovative punching layout, this paper shows how to minimize the high cogging torque of the mass-produced single-phase outer-rotor BLDC claw-pole motor—opposed to conventional cogging torque reduction—with no increase to the manufacturing cost. Systematically, a way is presented in which the selected introduction of auxiliary slots can double the cogging torque fundamental frequency, making stator claw skewing much more effective in reducing the cogging torque; both measures can be included at the stage of punching the steel sheets and subsequent deep-drawing thereof, at no additional cost. A detailed analysis of the effects of the cogging torque reduction measures on the most important motor performance parameters is conducted. The findings show that, with the exception of a three percentage point reduction in the efficiency, the proposed design can reduce the peak-to-peak cogging torque by 70% in both the simulations and experiments. The reduction in the cogging torque translates into a reduction in the output torque ripple of 17%, ensuring smoother operation especially at low speeds. [ABSTRACT FROM AUTHOR]

Open-switch faults in inverter-driven electric drives have recently gained increasing attention in the scientific community. Since these faults may lead to undesired effects, their fast and unambiguous detection is desirable. This paper proposes a detection algorithm for open-switch faults, which is based on the observation of the current control deviation and a subsequent test procedure. This algorithm detects the fault immediately after its occurrence within a few switching periods, even during transient operation. The proposed method is tested via simulations and experiments at different operating points of a surface permanent magnet drive. [ABSTRACT FROM PUBLISHER]

State-of-the-art design methods for electric machines use published correlations of either power or torque with electromagnetic and current loading, available for different cooling approaches. However, the applicability of these correlations for electric machines used within hybrid electric vehicles, with their different degrees of integration into the overall system, is limited. Using an integrated starter generator and an electric rear axle drive as example case applications, we study the influences of the thermal environment within the hybrid electric vehicle application, i.e., heat sinks and sources external to the machine on the thermal design of the machines. We quantify these influences by scaling factors for the air-gap shear stress of the machine. [ABSTRACT FROM PUBLISHER]

This paper describes a method for fast identification of the thermal behavior of vehicle integrated electric drives to propose a better understanding of electric machine design tailored to driving cycles. A simple, but satisfactorily accurate, calculation method for the estimation of machine losses, which is an input for the analytic thermal network, in the early design stage is introduced. The analytic models, which are verified using measurement data, are used for parameter and case studies for consideration of the thermal environment, with a focus on the gearbox. The first case study analyzes the influence of the gearbox on the thermal behavior of critical machine components. Aiming to use the gearbox lubricant for cooling the winding heads, an improvement of machine performance using an alternative cooling approach, which cools down the end windings, is shown in the second case study. [ABSTRACT FROM PUBLISHER]

Permanent magnet brushless dc (BLDC) machines are widely used due to various advantages such as high efficiency and high torque density, and therefore compactness as well as long expected lifetime. All of these benefits are of major interest when designing a drive for a small fan application of a few watts. This paper presents the design investigations of a small single-phase BLDC motor for such an application. Notably, it discusses different constraints which arise during the design process and which may be of special relevance due to the particular given power level and application. [ABSTRACT FROM PUBLISHER]

We present an alternative approach to analytic force computation in permanent-magnet machines, focusing on the tangential forces that generate the armature and the cogging torque. We extend previously presented methods using conformal mapping to overcome the limits imposed by the singularity of the magnetic flux density at the tooth tip that occurs during the transformation. Using our approach, the cogging and armature torques developed in lightly loaded electric machines can be computed without these limits and without introducing auxiliary parameters. We also revisit Maxwell's stress theory to compute the force on the interface of two materials with different permeabilities, in contrast to the common application to compute the force on a rigid body placed in an electromagnetic field. Using this technique, we then calculate the forces at the slot sides so that the influence of the machine design parameters on the result is directly available. [ABSTRACT FROM AUTHOR]