Power supply for screened equipment enclosure - incorporates low pass filter on isolating transformer secondary side and overvoltage discharge elements on primary side

摘要

The equipment components in a screened enclosure are fed from an AC source itself in a screened case. On the primary side of the isolating transformer discharge elements are connected to each input lead, to divert over-voltages to earth. A screen lead may be similarly protected. On the secondary side a low pass filter to eliminate electromagnetic impulses is connected to each lead. In single phase one end of the secondary winding is earthed to give voltage equalisation and the filter connected to the unearthed line. The filter typically provide damping of the order of 60 db in the range 10 to 10 Hz.