EPE Journal Volume 02-1 
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EPE Journal Volume 02-1 - Editorial
EPE Journal Volume 02-1 - Papers



 EPE Journal Volume 02-1 - Editorial 

Cooperation between universities and industry in Europe, as seen from Norway  [Details]
By T. Undeland

The Editorial of the EPE Journal Volume 2 N1, "Cooperation between universities and industry in Europe, as seen from Norway", written by Prof. Tore Undeland, Member of EPE Association's International Steering Committee.


 EPE Journal Volume 02-1 - Papers 

Industrial AC Drives, Status of Technology  [Details]
By V. R. Stefanovic

The technological reasons which are favoring AC drives as an alternative in adjustable speed applications are briefly summarized and the global trends, resulting from maturing of the AC drive technology, are examined. The developments of each of the drive sub-systems (static power converter, control and motor) are evaluated against industry requirements and the overall trends in their respective technologies are assessed.

Sensorless Position and Speed Control of a Brushless DC Motor from Start-up to Nominal Speed  [Details]
By A. Cassat; L. Cardoletti; M. Jufer

The brushless DC motors are sunchronous motors, self-commutated through a transistor bridge. The aim is to generate a magnetic field always positioned so that the torque is maximum. This principle needs a rotor position detection. Sensors as Hall effect devices, resolvers or optical disks are generally used. For small motors as those used in computer peripherics, it becomes impossible to implement such devices. Thus, the goal is to realize indirect sensors. The present paper describes a methodology to control a motor from standstill to full speed without direct position and speed sensors.

At standstill, the position is determined by short current pulses, enabling to detect indirectly the saturation level of the different phases. In order to avoid the temperature effect on the time constants, the measurement is converted into a current difference, with positive and negative current pulses in each phase. So, a logical state is defined, corresponding to the actual position with an angular accurancy of one electric period devided into 2m (m = number of phases). Such a method is necessary in order to assure a starting in the correct direction. A hazardous first switch on can let start the motor in the wrong direction. Consequently, the proposed system offers the possibility to start surely, without back oscillation.

The proposed system of position detection is used to start the motor from standstill to a medium speed, where the well-known method of the phase back E.M.F. position detection is applied. From medium speed to the nominal speed the motor is accelerated using the phase back E.M.F. position detection. Consequently, the motor is fully controlled in a closed loop sensorless mode from standstill to the nominal speed. The method is presented through a principle analysis, a process description and experimental measurements.

Monitoring an Ultra Fast Battery Charger with a ST6210 Micro-controller  [Details]
By L. Wuidart; P. Richter

Cordless and portable battery supplied equipments are proliferating thanks to the increasing capacity of rechargeable NiCd batteries. A usefull feature in applications where the battery is rapidly discharged, such as power tools, is the ultra fast charging in less then half an hour. The solution described in this paper is an efficient 100 kHz converter charging an NiCd battery in less then 15 minutes. The battery charge is monitored by a low cost micro-controller ST6210 enabling battery voltages identification, temperature monitoring and charge control.

Amplitude Control in Twelvepulse Voltage Source Inverters  [Details]
By K. Bouwknegt

The 12 pulse inverter is still widely used to combine a good sinusoidal waveform with a switching frequency of only 3 to 5 times the fundamental frequency of the inverter. Such a low switching rate has advantages in very high power inverters, in case of special requirements on low EMI or losses, or when the fundamental frequency is high.
This paper deals with VSI having pulse pattern control of the amplitude of the fundamental component of the output voltage . Some mathematical background in calculating the harmonics is given, as well as graphic optimisation of switching instants.

Multi-level Choppers for High Voltage Applications  [Details]
By T. A. Meynard; H. Foch

In the field of High Voltage Power Conversion, the circuit designer is often confronted to a serious problem: there are no semiconductors capable of sustaining the desired voltage (traction applications for example). The first solution involves plain series connection of several switches with synchronous control signals, thus obtaining the equivalent of a high voltage switch. Static and dynamic balancing of the voltage across the switches requires all the semiconductors to switch exactly at the same time; this requires selecting semiconductors with the same turn-on and turn-off times using control strategies capable of compensating the difference in switching time. In other respects, the output dV/dt at each commutation is the sum of the dV/dt generated by each switch, which is a serious stress for the environment and especially the firing circuits! The technique presented in this paper tolerates semiconductors switching at different times, thus allowing high voltage conversions with standard dV/dt. More, it will be shown that the control signals can be significantly phase-shifted to improve the harmonic spectrum of the output voltage.