This paper presents a practical approach to model and analyze transient thermal effects in air-cooled electric traction motors. The developed thermal modeling method enables accurate estimation of temperature in motor critical parts including winding and bearing. Advantages of both numerical and analytical modeling methods are exploited with the aim of realizing accurate estimation of hot spot temperatures in traction motors while keeping the computation time within a reasonable range. Computational fluid dynamics simulations are carried out to model air flow in the motor in order to provide heat transfer boundary inputs to the developed combined finite-element (FE) and lumped parameter (LP) thermal models. The combination of the FE and LP models keeps the size of the model relatively small and enables running transient calculations reasonably fast. Also, the developed model provides the possibility to study the influence of stator and rotor duct blockages on the motor thermal performance, which is a common root of failure in traction applications during operation in dirty environments. The proposed thermal model is verified using experimental results on a traction motor equipped with temperature sensors at different running conditions and a good agreement between the estimated and measured temperatures is achieved.

A high demand for electrification of the transport sector has resulted in a need to provide compact and reliable electric power trains where the electric machine is a key element. The cooling system has a strong impact on the specific torque and power capability of the machine. The selection of the cooling solution should not be based on the steady-state cooling performance only but also on the transient characteristics owing to the typical operational load nature of the propulsion system, where the load is not continuous (as it usually is in industrial applications), but it frequently varies in time depending on the vehicle type and the driving style. This article investigates in detail the cooling capabilities of a direct winding liquid cooling solution and compares it with a traditional frame liquid cooling arrangement in the transient condition. As a result of the comparison, it was found that the location of heat removal close to the heat source makes the temperature transient time faster, which allows to apply overload operating points more frequently.

Sinusoidal ripple-current charging has previously been reported to increase both charging efficiency and energy efficiency and decrease charging time when used to charge lithium-ion battery cells. In this paper, we show that no such effect exists in lithium-ion battery cells, based on an experimental study of large-size prismatic cells. Additionally, we use a physics-based model to show that no such effect should exist, based on the underlying electrochemical principles.

Modeling of electrical machines is a multiphysics problem. Depending on the phenomena of interest and the computational time constraint, this can be done at different levels of detail. In this paper, the main approaches to model the thermal behaviour of electrical machines with a liquid cooled casing around the stator (often referred to as cooling jacket) are analyzed and a novel approach is presented. The proposed method aims at creating computationally efficient 3D multi-physics models of electrical machines with liquid cooled jacket. This model is based on the assumption of a fully developed flow in the cooling jacket which allows to scale the CFD simulation to 1D. The slot with a two layer concentrated winding and potting material is modeled using a composite material comprising of both the conductors and slot filler. Similarly, a unified material is used to model the end-windings. Experimental results on a traction machine for vehicle applications are presented showing good agreement with the simulations. Also, a comparison with a 3D CFD is presented to verify the pressure drop in the pipe bend. Finally, the model is used to simulate a dynamic load cycle, which would be computationally extremely demanding with combined 3D CFD and thermal FEA of the machine and its cooling.

In this paper, a novel induction machine topology with wound, independently-controlled stator coils is presented. The introduced configuration of the stator-winding enables the individual energization and control of the coils in each stator slot. Therefore, the possibility of changing the number of poles and active phases in the stator winding during operation is explored in this study.

In the majority of applications using lithium-ion batteries, batteries are exposed to some harmonic content apart from the main charging/discharging current. The understanding of the effects that alternating currents have on batteries requires specific characterization methods and accurate measurement equipment. The lack of commercial battery testers with high alternating current capability simultaneously to the ability of operating at frequencies above 200 Hz, led to the design of the presented experimental setup. Additionally, the experimental setup expands the state-of-the-art of lithium-ion batteries testers by incorporating relevant lithium-ion battery cell characterization routines, namely hybrid pulse power current, incremental capacity analysis and galvanic intermittent titration technique. In this paper the hardware and the measurement capabilities of the experimental setup are presented. Moreover, the measurements errors due to the setup’s instruments were analysed to ensure lithium-ion batteries cell characterization quality. Finally, this paper presents preliminary results of capacity fade tests where 28 Ah cells were cycled with and without the injection of 21 A alternating at 1 kHz. Up to 300 cycles, no significant fade in cell capacity may be measured, meaning that alternating currents may not be as harmful for lithium-ion batteries as considered so far.