100 kV Integrated High-Voltage Module for Electrostatic Spray Robots

Industrial painting robots require the high-voltage generator to be mounted directly on the moving arm to eliminate corona loss in long supply cables and enable rapid color change, demanding a 100 kV, 300 µA module weighing under 1.9 kg with full environmental sealing against solvent vapors and paint overspray.

The integrated package uses a quasi-resonant flyback topology operating at 92 kHz with a gallium nitride primary switch driving a triple-insulated ferrite transformer and eight-stage Cockcroft-Walton multiplier fully encapsulated in solvent-resistant polyurethane. Total volume is 680 cm³ including control, feedback, and arc management circuitry.

Voltage control is performed by primary peak-current programming with a 180 kHz digital loop that maintains setpoint within ±0.6 kV across the full 0–300 µA load range created by varying gun-to-target distance. A fiber-optic feedback path from a resistive divider embedded in the multiplier eliminates ground-referenced noise pickup common in conductive paint bell applications.

Arc and short-circuit protection uses a two-level response: micro-arcs (<8 J) are quenched by instantaneous primary switch disable for 14 µs followed by soft restart at 65 % voltage; catastrophic shorts trigger full collapse to 4 kV for 180 ms with automatic cleaning cycle that pulses 28 kV reverse polarity to burn off conductive bridges. Average paint transfer efficiency remains above 78 % even with waterborne basecoats.

Robot motion compatibility is achieved through extensive EMI hardening: all control signals are fiber-isolated, the casing is a seamless carbon-fiber composite shield with conductive coating providing >120 dB attenuation to 3 GHz, and output cable uses low-tribo semiconductive silicone with active guard electrode that tracks gun potential within 180 V.

Color-change performance supports purge cycles under 11 seconds: the module ramps to 12 kV reverse polarity while purge solvent flows, then executes a 400 ms high-frequency burst at 38 kHz to ultrasonically dislodge residual paint from the bell edge before returning to forward voltage. No mechanical cleaning is required between colors.

These integrated 100 kV modules routinely achieve first-pass transfer efficiency above 82 % on complex automotive bodies with Class A surface requirements, while surviving 24/7 operation in explosive atmosphere zones with zero ignition incidents over five-year deployments.