Power Converter Characteristics

CERN is realizing a laboratory for the testing of high voltage storage capacitors with big capacitance values.

The testing laboratory comprises an AC source and a DC source. The AC source is constituted by 6 single phase H bridge power converters, while the DC source is made up by 2 six pulses diode bridges powered by an adjustable 3 phase voltage source.

The two sources provide a composite stress across the capacitors, made up of an AC sinusoidal voltage superposed to a DC one.

Maximum stressing values for capacitor under testing

Operation Responsibles

Responsibles:	Fulvio BOATTINI
	Charles GENTON
	Yves GAILLARD

Power Converter Architecture

This composite voltage is meant to supply a load constituted by a set of capacitors.

The capacitance value changes depending upon the test to be effectuated, with a maximum rms current fixed in 80Arms.

Power converter architecture

Power Part

The AC source is the most demanding in term of power. In-fact it has to provide all the kVAr needed by the tested capacitors.

The worst conditions are met when the testing of the fully sized element is required. To keep a limit, let’s consider the present capacitor value of 2mF; the following calculations give us the power needed:

The simplest DC source is a 3 phase diode bridge. For easier realization (and to keep compatibility with other testing requirements), a 12 pulse diode bridge is foreseen.

Two 6 pulses diode rectifiers are then connected in series.

The following values have to be considered for bridge sizing:

Control & Regulation Part

Control overview simplified schematic