| 摘要 |
The supply has a converter 10 coupled to a primary power source 12 for producing a converted voltage with a different frequency content to that of the source 12, the output of the converter 10 being connected to a step-up transformer 14 and a rectifier 20A to provide a high voltage fed to the precipitator 28A, 28B. The converter 10 may be an adjustable frequency, adjustable duty-cycle A.C. to A.C. converter supplied from a 60 Hz source and giving an output at a different frequency (Figs. 1, 2). The source 12 may be D.C. in some embodiments. In a further embodiment, the voltage applied to the precipitator is controlled by a micro-computer responsive to various current and voltage sensors, including means for sensing sparking and back corona. The conduction angle of thyristor Q1, Q2 is incremented from half-cycle to half-cycle of a 60 Hz supply 12 until the sensed conditions indicate that the conduction angle should be decremented or that the thyristor Q1, Q2 should be turned off. Every nth half cycle, e.g. every sixth half cycle, the conduction angle is increased to prevail throughout the majority of that half cycle, so that a high peak voltage is produced every nth half-cycle, these pulse peaks constituting the different frequency content (Figs. 6, 7). MOSFETS or a saturable reactor may be used instead of thyristors Q1, Q2. <IMAGE> |
