Lumped-parameter grey-box modelling of traction machines for low-speed operation

This paper presents a procedure to derive a thermal lumped-parameter grey-box model of an electric machine built for traction. The procedure includes experimental data logged under overload conditions for accurate temperature prediction at high currents, and features a relatively simple loss estimation approach. Validation of the model shows a good fit between measured and simulated results. Possible applications for the procedure are discussed in the end of the paper

Direct electromagnetic actuation on high ratio gears

This document demonstrates a conceptual study, design and development of unconventional electromagnetic actuators for applications where a high torque over a limited part of a rotational turn is required. The unconventionality of the actuators is that the electromagnetic actuation is applied directly on a high ratio transmission gear such as a cycloid disc in a cycloid drive or a flex-spline in a harmonic drive. Furthermore, normal forces are intentionally used to displace and rotate a cycloid disc or deform a flex-spline instead of tangential forces, which are typically used when integrating conventional rotating machine driving a high ratio gear transmission. The conceptual study is based on a number of finite element models where the idea is first presented and followed by field and force analysis. A finite element static model is used to calculate the expected excitation versus the gear location. The gear location of the cycloid disc is defined by an eccentric origin and rotation angle while the flex-spline is defined by a deformation and rotation angle. The analysis of the integrated normal force actuator inside the harmonic drive demonstrates the challenging strain gearing action in terms of elasticity and magnetic saturation. The challenge with the cycloid drive is the electromagnetic action force direction compared to the desired mechanic reaction force direction that causes unnecessary inner load or even locks the gear mechanisms. A prototype machine with the maximized rotor eccentricity is used to characterize four different rolling and geared cycloid transmissions

Dynamic Testing characterization of a synchronous reluctance machine

The Dynamic Testing Method has been shown to accurately characterize the electromagnetic model of Permanent Magnet Synchronous Machines by describing the relationship between the phase currents and the linked magnetic flux. Within this work, a performance evaluation of the Dynamic Testing Method applied to the Synchronous Reluctance Machine is presented. This paper discusses the difficulties of a dynamic test of a nonlinear synchronous machine and suggests a Fuzzy PD+I controller for improved control performance and measurements. Finally, the Dynamic Testing Method measurements are compared to results of the Constant Speed Method. The Constant Speed Method measurements of flux linkage and torque curves confirm the validity of the Dynamic Testing Method measurements for this machine

Characterization and application of forced cooling channels for traction motors in HEVs

This paper presents the characterization of forced cooling channels with three different shapes which are applied in traction motors mounted in Hybrid Vehicles (HEVs) or Zero Emission Vehicles (ZEVs). Generally, there are two different positions of forced cooling channels in electric motors. One way is by drilling holes or cutting cooling channels inside the housing, which is called indirect cooling approach. The other way is to cut the cooling channels at the edges of housing or/and stator back to form direct cooling channels, where the coolant is in direct contact with the hot stator back. In both cases, choosing suitable shapes of cooling channels are necessary. In this paper, both heat transfer coefficient hf and pump power Wpump are calculated. The dimensional parameters are easily understood and also used for further thermal analysis of the completed machine by either Finite Element Analysis (FEA) or lumped parameter approaches. In addition, the dimensionless parameters Nusselt number Nu and Darcy friction factor f are evaluated with the aim to understand the characterizations for different channels. These parameters are easily used for further cooling channels optimization. In the end, the thermal analyses for a stator segment with three different shaped channels are carried on by applying the calculated results from Computational Fluid Dynamics (CFD) simulations

Direct Conductor Cooling in Concentrated Windings

This paper presents and assesses the cooling integration of electrical machines with concentrated windings. A conventional coil in a concentrated winding with forced cooling applied on the exterior coil surfaces is replaced by an alternative solution where the coil is opened up in a laminar structure with the intention of the coolant fluid penetrating the coil and removing the interior heat. This is a purely theoretical study where a set of FE models are used to evaluate the torque capability under elevated thermal loads, comparing conventional to alternative cooling integration topologies. The objective of the unsophisticated FE evaluation models and simple design rules is to demonstrate the potential of the laminated type of windings where the space between the current carrying flat conductors is used to circulate coolant so that the heat losses are removed in the vicinity of where they are generated. Conjugate heat transfer analysis in Comsol multiphysics based on 2D and 3D is used to demonstrate the cooling capability for air and oil cooled windings up to thermal loads corresponding to 50 A/mm2at 24 nΩm and a target hot spot temperature of 120°C for copper

Direct Conductor Cooling in Concentrated Windings

This paper presents and assesses the cooling integration of electrical machines with concentrated windings. A conventional coil in a concentrated winding with forced cooling applied on the exterior coil surfaces is replaced by an alternative solution where the coil is opened up in a laminar structure with the intention of the coolant fluid penetrating the coil and removing the interior heat. This is a purely theoretical study where a set of FE models are used to evaluate the torque capability under elevated thermal loads, comparing conventional to alternative cooling integration topologies. The objective of the unsophisticated FE evaluation models and simple design rules is to demonstrate the potential of the laminated type of windings where the space between the current carrying flat conductors is used to circulate coolant so that the heat losses are removed in the vicinity of where they are generated. Conjugate heat transfer analysis in Comsol multiphysics based on 2D and 3D is used to demonstrate the cooling capability for air and oil cooled windings up to thermal loads corresponding to 50 A/mm2at 24 nΩm and a target hot spot temperature of 120°C for copper

Statistical Assessment of Core Loss Measurement Techniques for Laminated Steel

In this paper, a comparative study of core losses in laminated steel samples by means of inferential statistics is presented. In particular, core loss measurements taken upon Epstein Frame, Single-Strip tester, and Ring Core specimens at several frequencies and induction levels are compared via Analysis of Variance and two-sample t-tests. The hypothesis of a statistically significant difference among the testing procedures is sustained and ring cores showed a lower magnetic performance when compared to Epstein Frame and Single-Strip tester