J. Pyrhönen

Control of zero-sequence current in parallel connected voltage source PWM rectifiers using converter-flux-based control

A new zero vector selection strategy for the converter flux based control (CFC) of voltage source PWM rectifiers is introduced. With this strategy the circulating current in paralleled rectifiers is effectively suppressed and independent operations of the individual converter units are achieved. In addition to normal line filter, no additional passive components such as transformers or current sharing reactors are required to parallel the converters. Simulation and experimental results validate the developed model and the proposed zero vector selection scheme

Test results with the direct flux linkage control of synchronous motors

Synchronous motors are important in large drives. The application of the direct flux linkage control (DFLC) in synchronous machine drives is examined. This control method guarantees the best possible dynamics for the drive. Torque steps the height of which correspond to the motor nominal torque are achieved within a few milliseconds.

Uncertainty in motor efficiency measurements

Results of five induction motor efficiency measurements according IEC 60034-2-1 are presented. The uncertainty of the measurements is analyzed using scientific and numerical methods.

Motion synchronization of two linear tooth belt drives using cross-coupled controller

Different assembly, printing and cutting applications demand often fully synchronized movement of multiple actuators. The linear tooth belt drive offers an inexpensive and fast solution for linear movement applications. In this paper the cross-coupled controller is implemented and tested with biaxial linear tooth belt drive system for motion synchronization. The elastic tooth belt set uncertainty in the system parameters and the quantitative feedback theory is applied to design controllers for the biaxial system. Due to an elastic belt stretching phenomena system accuracy is analyzed using two different feedbacks with cross-coupled controller - firstly values are measured from driving motors encoders and secondly from belt drives load carts.

Indirect tension control method for an intermittent web transport system

Tension and conveyance in web-handling machines should be controlled accurately to ensure high product quality. Unlike typical web handling applications, the motions in discontinuous web transport process are typically fast, and thus, dynamically more demanding. Conveying the web in a discontinuous way brings new performance requirements for position and tension control. In this paper, a simple control method is proposed for dynamic tension regulation in a discontinuous web transport system. The web tension is controlled indirectly based on feedback information about position difference between two rollers. The tension controller is implemented in parallel with the speed controller. The parallel control structure improves dynamic reaction to changes in the web tension. The performances of the mathematical model and the controller designed are tested with experimental tests. The tension controller is implemented as part of the frequency converter control structure. The effectiveness of the tension control in dynamical web handling is studied with simulations and by experimental tests.

Modelling of low inductive busbars for medium voltage three-level NPC inverter

Design of low inductive busbars for medium voltage Neutral Point Clamped (NPC) inverter is studied. In a hard-switched inverter the stray inductance causes various problems, such as over voltages, current unbalance, and possible resonance with DC-link capacitors. These problems lead to improper operation of the inverter and an increased level of electromagnetic interference (EMI). The laminated busbars are known to be a good solution for minimizing the stray inductance. It is important to estimate and minimize the stray inductance of the busbars in an early design stage. FLUX3D is used to compare three physical layouts and analyze the influence of the placement of the main circuit components on the inductance value.

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 efficiency of hoisting motors

This study concentrates on energy efficiency of hoisting motors in industrial cranes. Motors in the scope are of three-phase cage-induction type and specially designed for intermittent duty S3. The main focus is on converter-fed motors. For a motor of certain rated power dimensions and rotor material are varied and electrical efficiency as a function of load is calculated. Energy consumptions for typical load spectra and operating hours are determined and compared to the energy consumptions of material production. It is shown that for light loads and infrequent usage manufacturing phase constitutes a significant part of the total energy consumption. Thus, increasing the efficiency of a motor may not provide notable energy savings. However, at high loads and operating hours better efficiency decreases the life-cycle energy consumption of an intermittent duty motor as well.

Recursive identification of linear tooth belt-drive system

Tooth belt drives with directly connected permanent magnet servo motors are mechanically very flexible systems, and the resonances of the system change significantly as function of cart position and load. This paper addresses issues in identification of a linear tooth belt-drive with limited stroke. Particular attention is paid to detecting the changes in the system dynamics. This is achieved by using recursive least squares algorithm and exciting the system in different cart positions in order to identify the varying dynamics. Moreover, the direct identification in open-loop as well as under closed-loop conditions is considered. The identification of linear tooth belt drive is evaluated by simulations as well as through experimental tests.

P.M synchronous generator design analytical method

Often P.M. synchronous generator designer finds some difficulties in matching the different quantities that conform the machine design; load requirements (V, i and cosφ), machine sizing, proper election of electrical circuit parameters and amount of permanent magnets on the excitation system. In addition to that, appears the difficulty of taking into account the effect of saturation. In the specialized literature can be found many methods in order to obtain a good compromise between the mentioned quantities, however they implicate approximate solutions and, in many cases, in despite of other indexes or parameters. The proposed Analytical Method overcomes these design problems starting from the two fundamental physical laws: Ampèrè s theorem and power balance. Also it is important to have an insight of the heat transfer and heat evacuation system, in order to determine the machine sizing. Optimization was carried out for maximal efficiency.