Gas-cleaning techniques using nonthermal plasma are slowly introduced into industry nowadays. In this paper, we present a novel power modulator for the efficient generation of large-volume corona plasma. No expensive high-voltage components are required. Switching is done at an intermediate voltage level of 1 kV with standard thyristors. Detailed investigations on the modulator and a wire-plate corona reactor will be presented. In a systematic way, modulator parameters have been varied. Furthermore, reactor parameters, such as the number of electrodes and the electrode-plate distance, have been varied systematically. The yield of O radicals was determined from the measured ozone concentrations at the exhaust of the reactor.