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The aim of this paper is to analyse the possibility of applying a topology of an eighteen-pulse thyristor rectifier for the electromagnet power supply. The scope was to determine if the proposed rectifier topology, with the two input interphase transformers, as well as the output one, can work with an output current ripple being less than 100ppm, with the acceptable dynamic characteristics of the voltage controller. Using the computer simulation, it has been found that, with a medium output filter capacitor and distinctively non-symmetric input parameters, the rectifier can work with an output current of approximately 80ppm of the DC component. If the input phase voltages were equalized, the effective value of the output current ripple could be reduced down to 17ppm. In both cases, satisfactory dynamic characteristics of the voltage controller have been achieved. The dominant influence on the output current filtering had the output interphase transformer magnetization inductance, as well as the capacitance of the filter capacitor. Increase of their values leads to better filtering of the output current, but also to a significant deterioration of the AC/DC converter dynamic characteristics. Measures for harmonization of the output low-pass filter characteristics and the PI voltage regulator parameters are proposed.

U radu je analiziran rad tiristorskog usmjerivača Simoreg DC Master koji se sastoji od dva tiristorska mosta u antiparalelnom spoju. Kao regulirani pogonski stroj stavljen je istosmjerni motor s nezavisnom uzbudom. Analizirana su pogonska stanja motora te je prikazan 4-kvadratni rad pretvarača. Fokus je stavljen na analizu i prikaz načina prijelaza u radu pretvarača s jednog na drugi tiristorski most. This paper analyzes the operation of the thyristror converter Simoreg DC Master consisting of two thyristor bridges in an inverse-parallel. As a regulated drive it is installed a separately excited DC motor. It is analyzed and displayed four quadrant drive. The focus is placed on the analysis and presentation of the transmutation mode of operation from one to the other of the thyristor bridge.

In this paper was presented the technical procedure implemented for the fault diagnostics of the thyristor bridge in an АС/DC converter. During the development of the new generation of digital controllers for AC/DC converters, it was required for these devices to have a possibility for a real-time detection of the thyristor converter fault. Thyristor bridge fault should be detected without the need for the state monitoring of the particular power semiconductor switches or rapid fuses. Thyristor bridge fault was identified using the measurement of the line-frequency second harmonic in the rectifier output current signal. Output voltage and current waveforms were presented, as well as the current spectra, in the cases of the thyristor bridge operation without one switch. The operation principle was described for a protection from an asymmetric operation of a thyristor bridge. A negative influence of high-order harmonics was analysed on the particular rectifier components, both in the cases of the output voltage control, as well as for operation in the current limit mode.