High frequency noise reduction of high-precision machine grounding system

Abstract

        High-precision machine mostly employs linear motors controlled by PWM (Pulse Width Modulation) technique. PWM technique inherits high instantaneous rate of voltage change over time (dV/dt); consequently electromagnetic emission has generated a noisy environment and leads to Electrostatic Discharge (ESD) events that pollutes sensitive devices such as recording heads for Hard Disk Drive (HDD) industry. This work proposes the noise reduction technique through grounding modification specifically for high frequency noise by using SPICE simulations and experiments. The high frequency modeling concern was taken into an account by including the Skin Effect of the high-precision machine on the SPICE model. Model accuracy was verified with the comparison between the simulations and experimental results. The electrical model was later on used as a core for analysis and redesigning the grounding system with two approaches to handle high frequency noise. First is to reduce resistance to ground by adding and reconfigurating the ground path using wires. Second is to introduce a capacitive path. The first approach can reduce the induced voltage at machine down to 4%; on the other hand, the second method can drain the voltage down to 76%.