Paula Immonen

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.

Design of a Traction Motor With Tooth-Coil Windings and Embedded Magnets

Traction motor design significantly differs from industrial machine design. The starting point is the load cycle instead of the steady-state rated operation point. The speed of the motor varies from zero to very high speeds. At low speeds, heavy overloading is used for starting, and the field-weakening region also plays an important role. Finding a suitable field-weakening point is one of the important design targets. At the lowest speeds, a high torque output is desired, and all current reserves of the supplying converter unit are used to achieve the torque. In this paper, a 110-kW 2.5-p.u. starting torque and a maximum 2.5-p.u. speed permanent-magnet traction motor will be studied. The field-weakening point is altered by varying the number of winding turns of machine. One design is selected for prototyping. Theoretical results are verified by measurements.

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.

Multidisciplinary Design of a Permanent-Magnet Traction Motor for a Hybrid Bus Taking the Load Cycle into Account

An electrical and mechanical design process for a traction motor in a hybrid bus application is studied. Usually, the design process of an electric machine calls for close cooperation between various engineering disciplines. Compromises may be required to satisfy the boundary conditions of electrical, thermal, and mechanical performances. From the mechanical point of view, the stress values and the safety factors should be at a reasonable level and the construction lifetime predicted by a fatigue analysis. In a vehicle application, the motor has to be capable of generating high torque when accelerating, and in normal operation, the losses of the machine should be low to be able to cool the machine. Minimization of the no-load iron losses becomes a very important electrical design requirement if the traction motor and the generator are mechanically connected with an internal combustion engine when it is operating as the only source of torque. The manufacturing costs of the motor are also taken into account in this paper.

The design of rotor geometry in a permanent magnet traction motor for a hybrid bus

The paper addresses the electrical and mechanical design process of a traction motor for a hybrid bus application. In general, the design process of the electric motors requires intimate co-operation between different engineering disciplines. Often compromises are needed in order to satisfy both the electrical and mechanical performance specifications. From the mechanical point of view the stress values should be on reasonable level and safety factors should be taken into account. From the electrical point of view the torque level should be high while accelerating the traction motor and the losses of the machine should be small in order to be able to cool the machine and sustain high efficiency. In traction use the no-load iron losses will be loading the overall system all the time - also while driving direct with diesel engine. While selecting the best rotor design also the costs will be taken into account - one expensive part of the motor is the permanent magnet material. Therefore, the material price is estimated when selecting the rotor design.

Energy saving by hybridization of a city bus

Energy efficiencies of different hybrid systems are investigated in an urban bus cycle. A diesel bus is converted into a multihybrid bus also capable of operating in a direct diesel drive. The target is to investigate which kind of a hybrid system provides the lowest fuel consumption in different operating conditions.

Component selection tool to maximize overall energy conversion efficiency in a pumping system

Often, the components of a pumping system are not selected from the perspective of the total system, as the individual components are selected using different programs. In this paper, a selection tool that optimizes the energy conversion efficiency of a pumping system according to actual process requirements is introduced. The tool requires only the catalog data of the components. Its application to an industrial pump system sizing, and thereby, to a component selection problem is demonstrated.

Energy saving in working hydraulics of long booms in heavy working vehicles

Abstract Hybridization of heavy off-highway working vehicles brings considerable energy savings in the form of a downsized internal combustion engine (ICE) by means of reduced no-load losses. In this paper, a novel energy saving opportunity in working hydraulics at the end of long booms of working vehicles is proposed. In traditional off-highway working vehicles, the working hydraulics is supplied through pipes, hoses, and valves by a hydraulic pump located near the main engine. A significant amount of energy is lost in long pipelines and hoses as well as in valve throttles. A new topology is introduced to supply the power along the long boom; the power for a hydraulic actuator is supplied by an integrated electro-hydraulic energy converter (IEHEC), which is located at the boom end. The electrical energy to the converter is supplied through electrical cables, which have negligible losses compared with a conventional fluid power supply with long pipelines. The converter transforms the electrical energy into hydraulic energy at the end of the boom, and may also recover energy for additional energy savings.

Modelling and simulation of a parallel hybrid drive system for mobile work machines

Hybrid drive systems have become more common during the latest decade not only in passenger cars but also in heavy vehicles and work machines. The tightening diesel engine emission standards will force manufacturers of work machines to develop their systems. Hybrid drive systems have a remarkable potential to reduce the emission of diesel-engined vehicles and work machines. This paper discusses the modelling, control strategies and simulation of diesel-electric hybrid drive systems.

Analyses of modular windings of a traction motor in a hybrid bus

Winding constructions are studied for a traction motor utilized in a hybrid bus. In vehicle applications, acceleration and deceleration require high torque. Thereby high current density is required intermittently while volume is adjusted to minimum. However, mobile converters may have a limited current output. This current amount is usually not enough for heavy drive cycles. Therefore, the authors designed a traction machine, which has two separate windings to be supplied by two separate converters. Therefore, the motors total current may reach higher values. Another important benefit is that the machine can be driven even when one winding or one supply unit is broken. In transportation use this may give the bus driver the possibility to drive to the destination or to a repair workshop. Several separated winding arrangements were designed and simulated with finite element method. A hybrid bus is designed and constructed at Lappeenranta University of Technology and the modular winding motor presented here has been applied in the bus.