engineering

The pulsed current source inverter is equipped with turn-off elements that operate with a pulse-width modulation to generate sinusoidal output currents. Therefore filter capacitors are necessary at the inverter output. Since the semiconductor elements must block reverse voltage, S-GTOs and SGCTs are used. The input converter feeding the dc inductor can be either a SCR-bridge (TFE) like with the LCI or a pulsed bridge (AFE) like the motor side inverter, which implicates additional input filter capacitors. Due to the pulsed elements a high output frequency of up to 220 Hz is possible. The inverter is simple in design and therefore reliable, but needs output capacitors, which have to be carefully designed. Field weakening is not possible, as well as high dynamic responses. The pulsed CSI is best used for general purpose 2Q and 4Q applications together with a standard induction motor. Thanks to the sinusoidal motor voltage and current there is no additional voltage stress on the motor, long cables are allowed and torque ripple and motor losses are low. Using a TFE there are the line side disadvantages as known from dc converters.

Power Section of Mv Drive

1 INTRODUCTION In industrial plants,it is often needed to supply several adjustable speed AC drives from a common DC link.Power electronics offers several technical solutions for supplying such drives from AC grid The technical solution with a common DC link and several inverters supplied from that DC linkis used in the case of several low power adjustable speed drives and in the case when a medium power driveisused.In the case of low power drives(effec- tive current up to 370A), it is possible tousecom- pactAC/ACconverters(Figure1).Ifa plant has more adjustable speed drives, more convenient sys- tem price is achieved using technical solution with the common DClink, supplied from anACgrid witharectifier(Figure2).Thesameis valid in the case ofseveral medium powerdrives (effective cur- rent 370–1200A), where each motorhas its own inverter, supplied from the common DClink. The reason forthis lies in the fact that forsuch power levels there are no commerciallyavailable compact AC/ACdrives. Supplyingthe DClink from an ACgrid is pos- sible with several types of power converters, The final choice of the common DC link supply converter depends on the drive demands (particu- larly regarding the braking), the converter power factor and the project budget. Forhigh power diode and SCR rectifier units it is possible to use parallel units supplied from two-secondary transformers,

Control and monitoring