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This paper presents an approach to the thermal design of an ac machine where the application requires low-duty transient operation. To provide accurate temperature predictions, the design process has been informed with experimental data from tests on a stator-winding sector (motorette). These have been shown to be a time and cost-effective means of calibrating the thermal model of a full machine assembly, prior to manufacture of the final design. Such an approach is usually adopted in design analysis of machines with a concentrated winding topology. Here, the motorette testing has been extended to a machine with a distributed winding. Several alternate slot liner and impregnating materials have been evaluated to maximize the heat transfer from the winding body into the machine periphery, and a total of nine stator section samples have been manufactured and tested. The performance tradeoffs between the various combinations are discussed in detail alongside their ability to satisfy the design requirements. Based upon these experimental results, the most promising designs have been selected for transient duty analysis against the design specification. A lumped parameter thermal model has been used for this purpose and calibrated using the data from the subassembly testing. Experimental results on the full machine assembly are presented, showing good correlation with the motorette calibrated thermal model. [ABSTRACT FROM AUTHOR]

This paper presents the results from a coupled thermal and power loss analysis of an open-slot permanent-magnet (PM) generator. The research focus has been placed on the winding design providing minimum power loss at an ac operation, together with low-cost manufacture. The analyzed PM generator is intended to operate at a fixed speed, allowing for the winding design to be finely tuned for a single operating point. Such a design approach has not been widely reported in literature, and the existing body of work is largely focused on variable-speed applications, where the winding design is a compromise between the low-speed and high-speed operating points for a given torque–speed envelope. The ac winding power loss has been analyzed for several winding variants with different conductor dimensions, accounting for the winding operating temperature. The calculated results suggest that, in the analyzed PM generator, a lower winding slot fill factor is preferable as compared with the more common approach, where the highest manufacturable winding slot fill factor is usually considered. The power loss predictions have been supplemented with the thermal analysis of the complete generator assembly for the winding variants considered, illustrating the importance and influence of the appropriate winding design on the power output capability of the fixed-speed PM generator. The most promising winding design for the minimum power loss at a rated operating point has been downselected for prototyping. The theoretical findings from the analysis have been compared with the experimental data from hardware tests on a stator winding section, showing close agreement. [ABSTRACT FROM PUBLISHER]

This paper presents the development of a hardware-in-the-loop (HIL) simulation system that facilitates the experimental testing of cell balancing circuits by emulating energy storage components. The system is developed with four cell simulators, each of which can emulate the battery voltage with the capabilities of sourcing and sinking current for the cell balancing circuit being tested. The cell simulator can also operate in battery testing mode for characterizing the behavior of a battery. One Li-polymer cell has been characterized using the cell simulator and a battery model has been built by the extracted parameters from the measurements. An active cell balancing experiment was conducted with a real 4-cell Li-polymer module followed by the same experiment using the HIL simulation system to emulate the Li-polymer cells based upon the method described in this paper. With the real battery module having a 9.4% SOC deviation initially, the final SOC deviation is reduced to 1.0% and the balancing time is 51.4 min. The HIL simulation gives very close results where the final SOC deviation and the balancing time are 1.2% and 52.0 min, respectively. The results demonstrate that the system can provide representative results for testing cell-balancing circuits with minimum resources and time. [ABSTRACT FROM AUTHOR]

The present paper describes an angle and speed estimation algorithm suitable for the control of a wound-field synchronous starter/generator (S/G) without position sensors for aircraft engine starting applications. The proposed control strategy is based on the injection of a high-frequency voltage signal and the subsequent demodulation of the resulting high-frequency stator current components. The coupling due to high-speed operation that degrades the estimation accuracy of similar algorithms based on signal injection is taken into account. Modeling of the machine response to a high-frequency voltage signal injected into the estimated d-axis is presented, also considering the influence of damping circuits both on the d- and q-axis. Local asymptotic stability of the proposed observer is also demonstrated. Through extensive experimental results, the proposed control technique is shown capable of guaranteeing full-torque sensorless operation at zero speed and sustained operation up to engine ignition speed. [ABSTRACT FROM AUTHOR]

A simple analytical technique, which uses readily available datasheet parameters, is developed to model the low-current switching characteristics of insulated-gate bipolar transistors (IGBTs). Simulation and experimental results obtained using three differently rated inverters are presented to demonstrate the accuracy of the technique. The model is applied to compensate the nonlinear distortion, introduced by IGBT switching action in a three-phase inverter, of high-frequency injected voltage and current signals used in sensorless control of a permanent-magnet brushless ac machine. Experimental results show that the compensation technique improves rotor position estimation by up to 20^\circ electrical. [ABSTRACT FROM AUTHOR]

Discusses the unification of the Lorentz and Coulomb gauges of electromagnetic theory. Velocity gauge condition; Physicality of the velocity gauge.