Search

This work proposes an active thermal management technology that operates ac drive inverters safely at thermal limits to maximize their current and torque capability. For that purpose, the technology exploits two fundamental opportunities: First, it monitors the coolant and junction temperature to adaptively determine the maximal peak current capability that increases at low coolant temperature. Second, it takes advantage of the thermal impedance frequency response function $Z_{\mathrm{th}}(\text {j}\omega)$ that decays with higher frequencies. Thus, larger currents are feasible at higher excitation frequencies without increasing peak junction temperature, because the associated transient losses are absorbed by the thermal capacitance of the power module. This article presents a unique active thermal management algorithm that addresses the two identified opportunities. It utilizes primarily a reduced-order electrothermal real-time model as well as negative temperature coefficient thermistor temperature information. Thus, it can be applied on most drive systems with small software modifications to adaptively maximize its current capability. To make this technology applicable in ac drives, this article also proposes torque control strategies that utilize variable current limits and discusses essential design limitation. With the introduced technology, state-of-the-art drive inverters can operate safely at up to 200% overload current and torque across a wide speed range. This supports the development of highly reliable drives with increased base speed range and power density that save space, cost, and resources. [ABSTRACT FROM AUTHOR]

To effectively find an optimal solution in the development process of electrical machines, it is essential to predict machine iron loss and thermal behavior in the predesign stage. Most existing publications only consider thermal behavior by roughly limiting the maximum current density. However, especially for high-speed application, iron loss can also be an essential part in thermal-behavior estimation. This paper proposes a simplified model to efficiently calculate iron loss and thermal behavior in the design procedure of switched reluctance machines. For this purpose, a maximum coenergy loop control method is implemented to facilitate the estimation of flux waveform and machine torque. Three different iron loss calculation methods are compared in terms of accuracy and time. Besides, a simplified lumped parameter thermal network is applied for machine sizing. Furthermore, the impact of number of turns and peak magnetomotive force on the losses and machine sizing is discussed. The efficiency and power density of various machine geometries are comparatively analyzed. Finally, the accuracy of the simplified model is verified by comparison with finite element simulations and experiment results. [ABSTRACT FROM AUTHOR]

Steadily increasing power demands are linked with the ongoing process of electrifying the powertrain for dominant and pure electric vehicles. Fulfilling those requirements can be achieved by a multiphase approach which is implemented with a six-phase machine with buried permanent magnets. Besides the new modelling aspects, new control possibilities arise such as controlling the current harmonics individually using vector space decomposition (VSD) methods. Here, this method is used to influence the noise, vibration and harshness (NVH) maintaining the working point in torque and speed. A reduction up to 22 dB of the main acoustic order in the significant speed range was achieved. [ABSTRACT FROM AUTHOR]

To effectively find a valid solution in the development process of electrical machines, it is essential to predict machine iron loss in the pre-design stage. In guidance on the choice of the most suitable configuration of the switched reluctance machine (SRM) is given, but iron loss prediction is neglected. Based on the study of Burkhart et al., this study proposes a simplified model to efficiently calculate iron loss in the design procedure of SRMs. For this purpose, a maximum co-energy loop control method is implemented to facilitate the estimation of flux waveform and machine torque. Three different iron loss calculation methods are compared in terms of accuracy and time. The accuracy of the simplified model is verified by comparison with finite element simulation results. Furthermore, the impact of different parameters on the iron loss is discussed, and the iron loss of various machine geometries is comparatively analysed. [ABSTRACT FROM AUTHOR]

In this paper, the intermittent control is proposed for switched reluctance machine (SRM) drive to both increase the efficiency and decrease the cost of the traction system for low-cost electric vehicles. With the purpose of maintaining the average machine torque required by the load, the intermittent control imposes a higher phase torque during a shorter time. The simulation and experimental results achieved with three different SRMs show that the intermittent control increases the system efficiency by reducing the converter losses and the core losses. Additionally, three different strategies of the control have been proposed to analyze their impact automotive application based on the criteria of efficiency, machine vibration, and torque pulsation. It can also be easily applied for any SRMs using average-torque-control-based methods. [ABSTRACT FROM AUTHOR]

This paper examines the efficiency performance of an automotive-size high-speed switched reluctance drive. It investigates the impact of a smooth torque control algorithm on the efficiency and losses in the drive. In automotive drives, the application of a dedicated algorithm for torque ripple reduction at low to medium speed is indispensable to avoid excitation of mechanical resonances in the drive train. The predictive direct instantaneous torque control method is compared with efficiency optimized hysteresis current control in terms of efficiency. Dynamic finite-element loss analysis is employed to investigate the source of the efficiency deviation and the results are verified by measurements. The study shows that the requirement for smooth torque leads to a decrease in the drives efficiency and altered loss distribution. The efficiency map comparison reveals that the efficiency degradation amounts to 4–9% for this particular drive. [ABSTRACT FROM PUBLISHER]

Zero-volt loop (ZVL) algorithms are known to be able to reduce peak flux linkages and resulting iron losses while keeping the same average torque in average torque control (ATC) of switched reluctance motors (SRMs). However, exploiting ZVLs to minimize the losses has been challenging due to the strongly nonlinear correlations between the torque and the control parameters of ATC caused by extensive magnetic saturation. In this paper, a fast optimization method for loss minimization is proposed, which can utilize all control parameters of ATC while operating with ZVL control. The proposed optimization method quickly calculates the current reference, which is one of the control parameters, so as to satisfy a torque reference, and consequently removes the time-consuming nonlinear constraint on the torque from conventional optimization methods. Using the proposed optimization method, the impact of ZVL control in loss minimization of SRMs is investigated with detailed simulations and experiments. The results verified that the utilization of ZVLs reduces iron losses without significantly increasing copper losses. It was found that the loss reduction was especially large (more than 15%) at medium speed and partial load. The loss reduction in the Japanese JC08 driving cycle for automotive propulsion for city driving was investigated and was as large as 15%. Furthermore, the vibrations that cause acoustic noise were also reduced. [ABSTRACT FROM AUTHOR]

This paper presents the design and an encoder-based starting strategy for a low-cost single-phase switched reluctance machine (SRM). The single-phase SRM cannot produce a continuous torque over one revolution. Therefore, applications that do not require a continuous torque, e.g., pumps and fans, are especially suitable. Another issue of single-phase machines is start up. The starting direction is affected by the initial rotor position. Due to the functional concept of SRM the machine produces no torque at aligned and unaligned position of the rotor and consequently, cannot be started from these positions. To start up from every rotor position a saturation-based starting method is used. The design of the rotor with the saturable area is shown and the principles of an encoder-based starting strategy for a fast start-up under 0.5 s are introduced. Finally, the build prototype and experimental results of the starting strategy are shown. [ABSTRACT FROM AUTHOR]

Torque control of a spherical machine combining three degrees of freedom in motion is presented. This drive can be used for machine tools and robots to replace conventional rotating or linear machines which are connected in series or parallel. The proposed motor consists of a rotor sphere with permanent magnets and an outer stator core casing with 96 stator poles and windings. The currents of the stator coils have to be controlled individually because the pole pitch can vary continuously during operation. A unique solution to calculate all 96 current commands to produce the desired torque does not exist. Different control algorithms are presented on how to choose the individual phase currents to reach the required torque vector. Simulations show satisfying results which are confirmed by experiments. In addition, the control- lability of three-dimensional motion is demonstrated. [ABSTRACT FROM AUTHOR]

Presents an online instantaneous torque control technique for switched reluctance machines called direct instantaneous torque control (DITC). Estimation of instantaneous torque; Theoretical and practical operating range of DITC; Results of simulation and experimental tests.

Presents a study which developed a technique to estimate online average torque of switched reluctance machines. Estimation of the average torque; Simulation of the operating principle of the torque estimator under dynamic conditions; Control variables for direct average torque controller.