HV generator regulating loop for electrostatic spray guns - has piezoelectric transducer reducing current as voltage falls enabling earthed object spraying

摘要

The regulating loop has a piezoelectric transducer consisting of ceramics containing lead, titanium and zirconate. The transducer controls the high voltage generator output current so that it continuously decreases as the output voltage falls towards zero. A stabilising oscillator output is fed to the transducer, and its control input receives the rectified output of the transducer so that the oscillator frequency is kept at the transducer resonant frequency. The system enables the insides of long tubes to be sprayed which would normally be difficult because of the screening effect and the resulting discharge occurring when the spray head is close to an earthed object.