Lasse Laurila

Three-Dimensional Thermal Model of a Lithium Ion Battery for Hybrid Mobile Working Machines: Determination of the Model Parameters in a Pouch Cell

Effective heat transfer and protection against high operating temperatures are important, lifetime-affecting items in the design and operation of batteries, especially those intended for hybrid mobile working machines, where the peak power and current demands are high. This paper describes a methodology for the modeling of the electrical and thermal behavior of lithium ion pouch cells for hybrid mobile working machines. The model is produced by coupling the equivalent electrical circuit of the pouch cell and the 3-D pouch cell thermal model. The temperature dependence of the battery operation parameters is added to the model in order to analyze the influence of temperature on heat generation during battery operation. Determination of the parameters of the thermal model is carried out empirically based on the presented methodology, which allows the construction of a 3-D thermal model of a pouch cell without requiring detailed information about the battery chemistry. The validity of the modeling procedure is demonstrated experimentally for a 60 Ah lithium titanate pouch cell.

Permanent Magnet Synchronous Machine Sizing: Effect on the Energy Efficiency of an Electro-Hydraulic Forklift

The energy efficiency of an electro-hydraulic forklift is significantly improved by using a permanent-magnet-synchronous-motor-servo-drive-based direct pump control to control the position of the fork without control valves. This paper provides a short evaluation of the hydraulic system and a more detailed analysis of the losses of the electric machine drive system. A theoretical approach is taken and the results are verified by practical measurements. Finally, possible improvements of the energy efficiency in the suggested system are discussed.

Measurements and Simulations of DTC Voltage Source Converter and Induction Motor Losses

Energy efficient pulse-width modulation inverters are widely used to control electrical machines accurately for process needs. The pulse-width modulation, however, has also adverse effects and produces additional losses in the motor. These losses increase the motor temperature and result in derating of the machine power in converter use. A reliable and reasonably accurate loss model of an induction motor drive system is important for the performance prediction of a variable-speed drive. A two-level frequency converter main circuit model is coupled to a finite-element method motor model. The drive model is controlled by closed-loop direct torque control. The frequency converter losses are calculated analytically, and the finite-element method motor model provides an analysis of the motor losses. The simulation results are compared with measurement results.

Electric energy recovery system efficiency in a hydraulic forklift

The purpose of this research is to find possibilities to recover electric energy in a hydraulic forklift system. The drive consists of a DTC controlled electric servo motor directly running a reversible hydraulic pump. A real system was built and tested, especially, from the energy recovery point of view. Results of the system were analyzed and compared and according to them, energy can be recovered efficiently from the hydraulic forklift system. Also new ideas and directions of further research were obtained during the research.

Loss calculation of a frequency converter with a fixed-step circuit simulator

The total losses of a frequency converter are calculated by using a fast fixed-step circuit simulator. A simple model for calculating the frequency converter total losses at different operating points is presented. Direct torque control (DTC) is applied as the control method of the converter. The simulated converter losses are verified by measurements.

Energy recovery efficiency comparison in an electro-hydraulic forklift and in a diesel hybrid heavy forwarder

Electro-hydraulic systems of heavy machines operating at different potential energy levels, using e.g. a lifting boom are evaluated. Practical results are found by using a light electro hydraulic forklift in measurements. A heavier diesel hydraulic forwarder is studied theoretically using the experimental results of the forklift as base data. An analysis of the efficiency of the energy recovery from a lifting boom of a forwarder is done.

Effect of PMSM sizing on the energy efficiency of an electro-hydraulic forklift

This paper investigates the effect of a permanent magnet synchronous machine (PMSM) drive on the efficiency of an electric energy recovery system of a hydraulic forklift. The control of the system is implemented directly with a permanent magnet AC servo motor drive without control valves. The paper provides accurate evaluation of the hydraulic system and the electric part of the working machine. An analysis of the theoretical model is made and the model is verified by practical results. Finally, possible improvements of the efficiency in the suggested system are estimated.

Effect of an Electric Motor on the Energy Efficiency of an Electro-Hydraulic Forklift

Mobile working machines can be classified as light mobile machines that operate by battery power and heavy machines that work using a diesel engine. Both of these types include mechanical structures, which are driven by hydraulics. With the rising concern in global scale environmental issues, energy saving in vehicles and mobile machines is an important subject and reduction of fuel consumption is strongly required (Petrone, 2010 ; Saber, 2010 ; Bhattacharya, 2009 ; Montazeri-Gh, 2010 ; Mapelli, 2010, Liu, 2010). Hybrid propulsion concepts in working machines are emerging to improve their fuel economy and reduce CO2 emissions (Fakham, 2011; Hui, 2010, Paulides, 2008). In addition, now there are government mandated Tier IV reduction regulations for harmful exhaust gases for diesel powered

DTC IM drive losses — Simulation and measurements

Pulse-width modulation (PWM) inverters are widely used to control electrical machines accurately for process needs, thereby increasing the system energy efficiency. The PWM methods, however, have also adverse effects and produce additional losses in the motor compared with the sinusoidal supply. Naturally, additional losses increase the motor temperature and, at least in principle, result in derating of the machine in converter use. A reliable and reasonably accurate loss model of an induction motor drive system is important for the performance prediction of a variable-speed drive. A frequency converter circuit model that includes an input choke, a diode rectifier, an intermediate DC circuit, and an IGBT inverter module is coupled to a FEM motor model. The drive model is controlled by closed-loop direct torque control (DTC). The frequency converter losses are calculated with analytical equations in a circuit model, and the FEM motor model provides the motor losses. The simulation results are compared with the measurement results.

Switching frequency harmonics of DTC IM drive in a system simulator with analytical and FEM motor model

Coupled system simulator based on FEM and analytical circuit equations is used to analyze direct torque controlled frequency converter fed industrial 200 kW squirrel-cage induction motor. The stator currents are analyzed in frequency domain. The performance of the FEM-motor model is compared with analytical motor model and the results are verified by measurements.