• Energy Research

An electrical variable transmission (EVT) is an electromagnetic device with dual mechanical and electrical ports. In hybrid electric vehicles (HEVs), it is used to split the power to the wheels in a part coming from the combustion engine and a part exchanged with the battery. The most important feature is that the power splitting is done in an electromagnetic way. This has the advantage over mechanical power splitting devices of reduced maintenance, high efficiency, and inherent overload protection. This paper gives a conceptual framework on how the torque on both rotors of the EVT can be simultaneously controlled by using a field-oriented control (FOC) scheme. It describes an induction-machine-based EVT model in which no permanent magnets are required, based on classical machine theory. By use of a predictive current controller to track the calculated current reference values, a fast and accurate torque control can be achieved. By selecting an appropriate value for the flux coupled with the squirrel-cage interrotor, the torque can be controlled in various operating points of power split, generation, and pure electric mode. The conclusions are supported by simulations and transient finite-element calculations.

An electrical variable transmission (EVT) is an electromagnetic device with dual mechanical and electrical ports. In hybrid electric vehicles (HEVs), it is used to split the power to the wheels in a part coming from the combustion engine and a part exchanged with the battery. The most important feature is that the power splitting is done in an electromagnetic way. This has the advantage over mechanical power splitting devices of reduced maintenance, high efficiency, and inherent overload protection. This paper gives a conceptual framework on how the torque on both rotors of the EVT can be simultaneously controlled by using a field-oriented control (FOC) scheme. It describes an induction-machine-based EVT model in which no permanent magnets are required, based on classical machine theory. By use of a predictive current controller to track the calculated current reference values, a fast and accurate torque control can be achieved. By selecting an appropriate value for the flux coupled with the squirrel-cage interrotor, the torque can be controlled in various operating points of power split, generation, and pure electric mode. The conclusions are supported by simulations and transient finite-element calculations.

The rotor design of Synchronous Reluctance Motors (SynRMs) has a large effect on their efficiency, torque density and torque ripple. In order to achieve a good compromise between these three goals, an optimized rotor geometry is necessary. A finite element method (FEM) is a good tool for the optimization. However, the computation time is an obstacle as there are many geometrical parameters to be optimized. The flux-barrier widths and angles are the two most crucial parameters for the SynRM output torque and torque ripple. This paper proposes an easy-to-use set of parametrized equations to select appropriate values for these two rotor parameters. With these equations, the reader can design a SynRM of distributed windings with a low torque ripple and with a better average torque. The methodology is valid for a wide range of SynRMs. To check the validity of the proposed equations, the sensitivity analysis for the variation of these two parameters on the SynRM torque and torque ripple is carried out. In addition, the analysis in this paper gives insight into the behavior of the machine as a function of these two parameters. Furthermore, the torque and torque ripple of SynRMs having a rotor with three, four and five flux-barriers are compared with three literature approaches. The comparison shows that the proposed equations are effective in choosing the flux-barrier angles and widths for low torque ripple and better average torque. Experimental results have been obtained to confirm the FEM results and to validate the methodology for choosing the rotor parameters.

The rotor design of Synchronous Reluctance Motors (SynRMs) has a large effect on their efficiency, torque density and torque ripple. In order to achieve a good compromise between these three goals, an optimized rotor geometry is necessary. A finite element method (FEM) is a good tool for the optimization. However, the computation time is an obstacle as there are many geometrical parameters to be optimized. The flux-barrier widths and angles are the two most crucial parameters for the SynRM output torque and torque ripple. This paper proposes an easy-to-use set of parametrized equations to select appropriate values for these two rotor parameters. With these equations, the reader can design a SynRM of distributed windings with a low torque ripple and with a better average torque. The methodology is valid for a wide range of SynRMs. To check the validity of the proposed equations, the sensitivity analysis for the variation of these two parameters on the SynRM torque and torque ripple is carried out. In addition, the analysis in this paper gives insight into the behavior of the machine as a function of these two parameters. Furthermore, the torque and torque ripple of SynRMs having a rotor with three, four and five flux-barriers are compared with three literature approaches. The comparison shows that the proposed equations are effective in choosing the flux-barrier angles and widths for low torque ripple and better average torque. Experimental results have been obtained to confirm the FEM results and to validate the methodology for choosing the rotor parameters.

Distortion of the supply voltage undoubtedly reduces the overall energy efficiency of induction motors. The goal of this paper is to evaluate additional harmonic losses in relation to the machine's initial efficiency rating. However, due to the relatively small amount of additional loss, the main drawback when evaluating the effect of supply voltage distortion on the machines' overall efficiency is the measurement accuracy of the current methods. In order to validate the effect of motor efficiency rating in relation to supply voltage distortion, the use of the parameter "harmonic active power" is suggested. This new strategy is subsequently validated by measurements and compared to current methods such as the NEMA MG1, or the procedure according to the IEC60034-2-3. Although this strategy is only valid under certain constraints, this new method enables a fast and highly accurate measurement of the additional loss. Consequently, this parameter is used to validate the effect of efficiency rating of induction motors in relation to the additional loss related supply voltage distortion.

Distortion of the supply voltage undoubtedly reduces the overall energy efficiency of induction motors. The goal of this paper is to evaluate additional harmonic losses in relation to the machine's initial efficiency rating. However, due to the relatively small amount of additional loss, the main drawback when evaluating the effect of supply voltage distortion on the machines' overall efficiency is the measurement accuracy of the current methods. In order to validate the effect of motor efficiency rating in relation to supply voltage distortion, the use of the parameter "harmonic active power" is suggested. This new strategy is subsequently validated by measurements and compared to current methods such as the NEMA MG1, or the procedure according to the IEC60034-2-3. Although this strategy is only valid under certain constraints, this new method enables a fast and highly accurate measurement of the additional loss. Consequently, this parameter is used to validate the effect of efficiency rating of induction motors in relation to the additional loss related supply voltage distortion.

The aim of this paper is to calculate the static eccentricity (SE) of a double rotor axial flux permanent magnet (AFPM) machine by using a general analytical model. The flux density in the air gap under healthy conditions is calculated firstly, where the axial and circumferential magnetic flux densities are obtained using a coupled solution of Maxwell’s equations and Schwarz-Christoffel (SC) mapping. The magnetic flux densities under SE conditions are calculated afterwards using a novel bilinear mapping. Some important electromagnetic parameters, e.g., back electromotive force (EMF), cogging torque and electromagnetic (EM) torque, are calculated for both SE and healthy conditions, and compared with the finite element (FE) model. As for the double rotor AFPM, SE does not contribute much effect on the back EMF and EM torque, while the cogging torque is increased. At each calculated section, FE models were built to validate the analytical model. The results show that the analytical predictions agree well with the FE results. Finally, the results of analytical model are verified via experimental results.

The aim of this paper is to calculate the static eccentricity (SE) of a double rotor axial flux permanent magnet (AFPM) machine by using a general analytical model. The flux density in the air gap under healthy conditions is calculated firstly, where the axial and circumferential magnetic flux densities are obtained using a coupled solution of Maxwell’s equations and Schwarz-Christoffel (SC) mapping. The magnetic flux densities under SE conditions are calculated afterwards using a novel bilinear mapping. Some important electromagnetic parameters, e.g., back electromotive force (EMF), cogging torque and electromagnetic (EM) torque, are calculated for both SE and healthy conditions, and compared with the finite element (FE) model. As for the double rotor AFPM, SE does not contribute much effect on the back EMF and EM torque, while the cogging torque is increased. At each calculated section, FE models were built to validate the analytical model. The results show that the analytical predictions agree well with the FE results. Finally, the results of analytical model are verified via experimental results.