CHARACTERIZATION OF METHODS FOR SURFACE CHARGE REMOVAL FOR THE REDUCTION OF ELECTROSTATIC DISCHARGE EVENTS

Khandakar Nusrat Islam, Doctoral Student, Electrical and Computer Engineering

Description

Electrostatic discharge (ESD) from charged dielectric materials used in explosive environments presents a significant hazard. In order to investigate dielectric surface charging and methods of removing this charge in a controlled manner, a test stand has been built to study the behavior of several common dielectric materials used in such environments. A corona discharge source of the type used in electrostatic printing technology has been employed at normal laboratory temperatures and at low and high relative humidity in a controlled manner. Dielectrics tested included black/semi-black/yellow Kapton, Lexan, Delrin, and red Adiprene with surface potentials (Vdiel) ranging from -1 kV to -15 kV. Uniform charging and discharging of individual dielectric samples of varying thickness have been characterized by spatial scans of the surface potential at relatively low voltages. At higher charging voltages, the surface potential is found to decay or increase with time in complex ways, showing a dependence on the magnitude of the surface potential Vdiel, as well as two characteristic time constants, td (�1, �2) in some cases. The initial discharge of vii Vd (td) is rapid, while the subsequent discharge of surface potential is found to be much slower. The decay time constant(s) is(are) found to be a nonlinear function of the surface voltage, Vdiel. A conductive brush and a static dissipative brush grounded on the metal plate is found the most effective method to remove the majority (typically 80-90%) of the surface charge, Qs. Additionally, it was found that localized discharging results in a constant electric field gradient, ∇� on the dielectric samples in 2D. A limited number of experiments have been conducted if there is any correlation between the tendency of a dielectric to charge more and the surface resistivity of the dielectric material. Experimental results from surface resistivity and chargeability on all tested dielectric at 10 kV show that the semi black/yellow Kapton charges even more than that materials have low resistivity than Lexan/Delrin. Even after 10 mins, yellow Kapton still retain a significant amount of charge than Delrin. An investigation on yellow Kapton with 0.127 mm thickness also shows that the higher relative humidity affects the surface resistivity significantly.

 
Nov 8th, 2:15 PM Nov 8th, 3:15 PM

CHARACTERIZATION OF METHODS FOR SURFACE CHARGE REMOVAL FOR THE REDUCTION OF ELECTROSTATIC DISCHARGE EVENTS

Bobo Room, Hodgin Hall, Third Floor

Electrostatic discharge (ESD) from charged dielectric materials used in explosive environments presents a significant hazard. In order to investigate dielectric surface charging and methods of removing this charge in a controlled manner, a test stand has been built to study the behavior of several common dielectric materials used in such environments. A corona discharge source of the type used in electrostatic printing technology has been employed at normal laboratory temperatures and at low and high relative humidity in a controlled manner. Dielectrics tested included black/semi-black/yellow Kapton, Lexan, Delrin, and red Adiprene with surface potentials (Vdiel) ranging from -1 kV to -15 kV. Uniform charging and discharging of individual dielectric samples of varying thickness have been characterized by spatial scans of the surface potential at relatively low voltages. At higher charging voltages, the surface potential is found to decay or increase with time in complex ways, showing a dependence on the magnitude of the surface potential Vdiel, as well as two characteristic time constants, td (�1, �2) in some cases. The initial discharge of vii Vd (td) is rapid, while the subsequent discharge of surface potential is found to be much slower. The decay time constant(s) is(are) found to be a nonlinear function of the surface voltage, Vdiel. A conductive brush and a static dissipative brush grounded on the metal plate is found the most effective method to remove the majority (typically 80-90%) of the surface charge, Qs. Additionally, it was found that localized discharging results in a constant electric field gradient, ∇� on the dielectric samples in 2D. A limited number of experiments have been conducted if there is any correlation between the tendency of a dielectric to charge more and the surface resistivity of the dielectric material. Experimental results from surface resistivity and chargeability on all tested dielectric at 10 kV show that the semi black/yellow Kapton charges even more than that materials have low resistivity than Lexan/Delrin. Even after 10 mins, yellow Kapton still retain a significant amount of charge than Delrin. An investigation on yellow Kapton with 0.127 mm thickness also shows that the higher relative humidity affects the surface resistivity significantly.