Shanelle N. Foster

Comparison between a spoke-type PMSM and a PMASynRM using ferrite magnets

Increasing concerns over costs and supply of rare earth magnets have introduced more attention to Permanent Magnet Synchronous Machine (PMSM) designs that can work with ferrite magnets. Ferrite magnets are weaker in comparison to rare earth magnets which makes it a challenge to achieve high torque density. In light of this, literature has introduced several PMSM designs that show an improved performance despite the challenges of ferrite magnets. This paper presents a comparison between the spoke-type PMSM design and the Permanent Magnet Assisted Synchronous Reluctance Machine (PMASynRM), both using ferrite magnets. The spoke type PMSM is based on an existing design, whereas the PMASynRM is designed by changing the configuration of the magnets in the rotor and using a lower number of poles. The PMASynRM design also incorporates some of the best practices from literature that are used to improve its performance. The objective is to determine which rotor configuration gives the best performance. In addition, a design used for quick implementation is presented. Finite Element Analysis (FEA) is used to analyze both designs, and some experimental results are shown.

Evaluation of a Parameter Identification Method for Permanent Magnet AC Machines Through Parametric Sensitivity Analysis

In this paper, the effectiveness of a simplified characterization method for permanent magnet machines is evaluated through performance sensitivity analysis. Performance sensitivity analysis is a novel way to evaluate the effectiveness of any identification method, as it investigates the effects of parametric errors upon the output performance of a machine. Parametric errors are due to inaccuracies during the identification process. This evaluation tool was validated using a 10-kW SmCo interior permanent magnet machine characterized using two different identification methods. A detailed identification procedure is used as the basis for evaluating a simplified method. The performance experimental data were collected using torque controllers based on the parameters extracted with both approaches. This information is used to perform the sensitivity analysis over the operating range of the machine. Finally, the results are compared and analyzed to determine the effectiveness of the simplified characterization method and its implications on the control performance.

High performance controllers for Interior Permanent Magnet Synchronous Machines using look-up tables and curve-fitting methods

Interior Permanent Magnet Synchronous Machines (IPMSM) used in hybrid powertrain applications are required to deliver high efficiency over wide speed and torque ranges. The performance of any control algorithm is directly dependent on the accuracy of the parameters. Saturation and cross-saturation of permanent magnet synchronous machines are well recognized phenomena. Developing a controller utilizing either a two-dimensional look-up table or linear approximation of the machine parameters generated from characterization data will include the effects of saturation and cross-saturation and thereby achieve the desired performance. Both the look-up table and curve-fitting methods are implemented on a microcontroller. A 125kW IPMSM drive is used to experimentally evaluate both methods. The work presented here demonstrates that both the look-up table and curve-fitting methods provide satisfactory performance over the entire operating range. A comparison of the complexity of implementing both methods is included.

A voltage based approach for fault detection and separation in permanent magnet synchronous machines

Different faults in Permanent Magnet Synchronous Machines will cause various and independent changes to the machine magnetic flux distribution, which will cause different changes to the machine parameters and performance. These changes will be reflected in the machine flux linkages, which can be determined from the machine voltages. In this paper, a method is proposed to detect and separate three types of faults in Permanent Magnet Synchronous Machines: static eccentricity, demagnetization and turn-to-turn short circuit. The proposed method is based on using the direction of the shift in the commanded d and q axis voltages while the machine is operating at steady state. Simulation tests using Finite Element Analysis software (MAGSOFT-Flux2D) were performed under healthy and faulted conditions on a 3 phase 10-pole fractional slot concentrated winding Permanent Magnet Synchronous Machine. Experimental tests were carried out and compared with Finite Element Analysis for the same machine under demagnetization and turn-to-turn short circuit faults. The effects of the speed and temperature variations were simulated to validate the detection method under different operating conditions.

Stator incipient fault identification in short secondary linear permanent magnet synchronous machines

Technology has advanced the reliability of electrical machines; however, machine failures still occur. Undetected stator inter-turn faults in permanent magnet synchronous machines can quickly propagate to catastrophic failure. In this work, unique signatures in the phase voltages of linear permanent magnet synchronous machines with a short secondary are used to detect and locate incipient turn-to-turn faults. Finite element and experimental results are presented to show that the d-q axis voltage variations due to the fault presence provide information required to both detect and locate.

Linear permanent magnet synchronous machine for high acceleration applications

In this work, a linear permanent magnet machine design is presented for applications that require high acceleration. This design uses aluminum as a supporting material for the moving secondary to reduce mass. Force production is maintained through the use of a quasi-Halbach array of permanent magnets. Aluminum, however, is conductive and the additional losses in the moving secondary lead to higher operating temperatures. The structural integrity of the moving secondary must also be maintained as the aluminum has lower material strength compared to other supporting tube material options. A comparison of material options and magnet array configurations highlights the advantages and disadvantages of the design options. Electromagnetic, thermal, and structural analysis of the selected design are carried out using finite element methods. Additionally, a prototype of the design is evaluated experimentally.

Online estimation of remaining useful life of stator insulation

Wide bandgap semiconductor devices in machine drive topologies are becoming more prevalent. These devices improve efficiency and can operate at higher switching frequencies. However, higher switching frequencies will increase the electrical stress applied to the insulation of the machine. Electrical stress, excessive heating, mechanical vibrations, and environmental contamination are leading factors that contribute to insulation degradation. Breakdown of the insulation will lead to a short circuit fault between two conductors. Short circuit faults can quickly propagate and lead to catastrophic failure. This project proposes an online method to accurately predict the remaining useful life (RUL) of the stator insulation by monitoring a trend in the leakage current. As the insulation degrades, the magnitude of the overshoot in the transient response of the leakage current exponentially decreases. An analog peak detection circuit is used to acquire this magnitude using low frequency sampling. An Extended Kalman Filter is applied to predict the RUL of the insulation. The proposed strategy will improve machine reliability, especially when using wide bandgap devices, while not requiring expensive or special equipment for assessing the health of the insulation.

Performance analysis of radial and axial flux fractional horsepower motors

This paper shows that axial flux motors are compact, torque dense, efficient replacements for radial flux fractional horsepower motors. A commercially available radial flux fractional horsepower motor is used as baseline for design of its axial flux counterpart. The torque density and losses of the radial and axial flux motors, with identical permanent magnet utilization factors, are compared with finite elements. An additional design is presented to demonstrate its ability to overcome the major challenge of axial flux designs without compromising performance.

Torque ripple reduction in interior permanent magnet synchronous machines with single-layer fractional slot concentrated windings

High power density and reliability associated with single-layer fractional slot concentrated winding interior permanent magnet synchronous machines make them appealing for automotive and aerospace applications; however, the associated magnetomotive force contains extra harmonic components that result in higher torque ripple. Mechanical vibrations, acoustic noise and bearing damage are often caused by torque ripple and can significantly reduce the life of the machine. In this paper, a priori estimation of torque ripple is used to decrease the torque ripple of a single-layer fractional slot concentrated winding design. Finite element and experimental results are presented demonstrating that the control technique is effective. The losses associated with this controller are also evaluated.