Sinusoidal and Triangular High-Voltage Neutralizers for Accelerated Discharge of Nonwoven Fibrous Dielectrics

Abstract

Electric charge accumulation on fibrous dielectric media during manufacturing processes can easily attain high levels of electrostatic hazard. In a previous paper, the authors addressed the problem of the accelerated discharge of such materials using a commercial ion generator. The aim of this paper is to evaluate the various factors that influence the efficiency of charge neutralization performed using a wire-type corona electrode energized from either a sinusoidal or a triangular ac high-voltage supply. The experiments were performed on 400-μm-thick nonwoven sheets of polypropylene and polyester, in ambient air. The samples were charged for 10 s using a triode-type corona electrode system of negative polarity. The surface potential on the charged medium, which was in contact with the grounded electrode, was then measured with an electrostatic voltmeter. After 10 min, the medium was moved beneath a neutralizing electrode, connected to a high-voltage amplifier. The efficiency of the neutralization was quantified by the ratio between the surface potential after and prior to the charged sample exposure to ac corona discharge. The experimental design methodology was employed for evaluating the effects of two factors, namely, amplitude (range: 16-24 kV) and frequency (range: 20-400 Hz), of the neutralizing voltage. The potential at the surface of the nonwoven fabrics after neutralization was found to vary insignificantly with thermal conditioning and signal waveform but was significantly lower for higher frequencies and amplitudes.