Vesa Ruuskanen

Direct-Driven Interior Magnet Permanent-Magnet Synchronous Motors for a Full Electric Sports Car

The design process of direct-driven permanent-magnet (PM) synchronous machines (PMSMs) for a full electric 4 × 4 sports car is presented. The rotor structure of the machine consists of two PM layers embedded inside the rotor laminations, thus resulting in some inverse saliency, where the q-axis inductance is larger than the d-axis one. An integer slot stator winding was selected to fully take advantage of the additional reluctance torque. The performance characteristics of the designed PMSMs were calculated by applying a 2-D finite-element method. Cross saturation between the d- and q-axes was taken into account in the calculation of the synchronous inductances. The calculation results are validated by measurements.

Dynamic Torque Analysis of a Wind Turbine Drive Train Including a Direct-Driven Permanent-Magnet Generator

Mechanical interactions between a wind turbine and a direct-driven permanent-magnet synchronous generator (PMSG) are studied, and a model to analyze the system behavior is suggested. The proposed model can be applied to analyze the mechanical vibrations of direct-driven wind turbine installations both in steady state and in dynamic cases. The cogging torque and torque ripple of the PMSG are used as excitation sources in the mechanical model. Four different permanent-magnet rotor constructions are analyzed. It is shown that the maximum allowable value of the cogging torque of the direct-driven permanent-magnet wind generator in this case is 1.5%-2% of the rated torque even when the corresponding resonance frequency does not occur in the operational speed range of the wind turbine. Furthermore, it was noticed that the resonance caused by the excitation torque should occur at the lowest possible speed.

Permanent-Magnet Length Effects in AC Machines

Permanent-magnet synchronous machines (PMSMs) are gaining popularity in the industry and, especially, in distributed generation, for instance in windmill applications. Some of the traditional analytical design principles seem not to be valid for permanent magnets in machine excitation. We report on the effects of the permanent-magnet length in machine design.

Drive Cycle Analysis of a Permanent-Magnet Traction Motor Based on Magnetostatic Finite-Element Analysis

This paper introduces a method for the drive cycle performance analysis of a permanent-magnet traction motor based on a fast magnetostatic finite-element analysis (FEA). The flux linkage and torque behavior of the permanent-magnet synchronous machine is studied by a nonlinear magnetostatic FEA as a function of direct- and quadrature-axis stator current components. In the analytical machine performance analysis, the current combinations producing the desired torque and minimizing the losses are determined. The iron loss is calculated with the time-transient FEA at no load. The maximum stator flux linkage, limited by the battery voltage, is taken into account. The drive cycle analysis, based on optimal current component surfaces, is carried out for a traction motor of an electric sports car. The results are compared with values measured for the drive cycle on a racetrack.

Effect of Lamination Stack Ends and Radial Cooling Channels on No-Load Voltage and Inductances of Permanent-Magnet Synchronous Machines

The effect of lamination stack ends and radial cooling channels on the effective stator stack length, no-load voltage, and synchronous inductances of a permanent-magnet synchronous machine are studied using three-dimensional finite element analysis. The stack ends and the radial cooling channels decrease the equivalent electrical length of the machine, thus leading to the fact that a two-dimensional (2-D) approach overestimates the no-load voltage. The effect of stack ends and radial cooling channels on the electrical length of the machine can be compensated by making the rotor stack and permanent magnets longer than the corresponding stator stack. It is shown that in case of no radial cooling channels, synchronous inductances are typically overestimated with the 2-D approach. However, in the case of stator structure having several radial cooling channels, inductances are underestimated using the 2-D approach.

Effect of Radial Cooling Ducts on the Electromagnetic Performance of the Permanent Magnet Synchronous Generators With Double Radial Forced Air Cooling for Direct-Driven Wind Turbines

Most of the high-power, low-speed, direct-driven permanent magnet synchronous generators for wind energy applications apply a cooling solution where the stator core is divided into a number of substacks. Cooling air is blown through the stator through radial cooling channels formed between the adjacent stator substacks. The use of the stator substacks has an effect on the equivalent length of the generator, and thus, if neglected, leads to an incorrect no-load voltage and synchronous inductance calculation. In this paper, the design issues related to the thermal and electromagnetic design of permanent magnet synchronous machines are highlighted. The analysis starts with a preliminary electromagnetic design. Then, the allowable number and width of cooling ducts are calculated based on the maximum allowable temperatures and fluid flow speed with a thermal resistance network model. The effect of cooling ducts on the no-load voltage and synchronous inductances of the machine are discussed in detail. The calculated no-load voltage and synchronous inductances are used in the analytical performance evaluation. It is shown that the cross-saturation of the synchronous inductances must be taken into account in order to get realistic results.

Original article: Lumped-parameter-based thermal analysis of a doubly radial forced-air-cooled direct-driven permanent magnet wind generator

A lumped-parameter-based thermal analysis of a direct-driven permanent magnet wind generator with double radial forced-air cooling is presented. In the proposed thermal model, the thermal conduction and convection as well as the heating of the cooling fluid are modeled in terms of thermal resistances. The electromagnetic losses of the generator are calculated by a two-dimensional, non-linear, time-stepping finite element method. The developed thermal calculation model can be applied both to static and transient problems. The performance of the proposed thermal model is compared with the results calculated by using computational fluid dynamics. The presented modeling strategy is implemented into an analytical calculation tool, which is used in the design process of a 3.35MW high-torque low-speed direct-driven permanent magnet synchronous generator. Experimental results for a 3.35MW permanent magnet generator are presented.

Iron Loss Analysis of the Permanent-Magnet Synchronous Machine Based on Finite-Element Analysis Over the Electrical Vehicle Drive Cycle

Fast methods to estimate iron losses of the permanent magnet traction motor during the drive cycle of the electrical vehicle are compared. The methods use the iron loss information calculated by a finite-element analysis as a function of rotational speed both at no load and with a short-circuited stator to take into account the variable frequency and field weakening of the traction motor. The effect of iron losses on the optimal current components, providing the maximum efficiency, is studied. Several methods yield a good accuracy even based on the no-load iron loss only, but the accuracy can be improved especially in deep field weakening by including the short-circuit iron loss information in the analysis.

Optimization strategies of PEM electrolyser as part of solar PV system

Solar and wind power have intermittent nature. In order to guarantee continuous power supply, they need to be accompanied with energy storage systems or bridges between different energy sectors. Hydrogen is a potential candidate for both applications (an energy storage system and bridging technology). Hence, it is interesting to study the practical dynamic properties and limitations of electrolysers in the viewpoint of renewable energy production. This paper studies optimization strategies of a proton exchange membrane (PEM) electrolyser together with a solar photovoltaic (PV) system.

Specific energy consumption of PEM water electrolysers in atmospheric and pressurised conditions

Power electronics enable the interconnection between renewable energy and electrolytic hydrogen production. At ambient conditions, the volumetric energy density of hydrogen is low, and therefore pressurisation is required. This paper studies the effect of the hydrogen outlet pressure from PEM electrolysers on the specific energy consumption of water electrolyser systems.