Current oscillation elimination for the helicopter transient electromagnetic inverter based on pole configuration

Abstract

In a helicopter transient electromagnetic system, the quality of the transmitting-current waveform will affect the geological exploration effect. In this paper, a helicopter TEM inverter, based on a single-clamp source and pulse width modulation technology, is designed and analyzed. Besides, it finds that there will be current oscillation in the early measuring stage. For this problem, first, the factors that cause the current oscillation are analyzed. Then, it is proposed to apply the RC snubber to eliminate this current oscillation. Since the imaginary part of the pole is the essence of oscillation, configuring the pole can eliminate the current oscillation. By establishing the early measuring stage system model, the characteristic equation of the load current with the snubber circuit is deduced. Next, the characteristic equation is solved by the exhaustive method and the root locus method to obtain the parametric region that eliminates the oscillation. Finally, through simulation and experimental verification, the proposed snubber circuit design method can be used to eliminate the early measuring stage current oscillation. Compared to the method of switching into the damping circuit, it can achieve the same performance, more important is that there is no switching action and it is easy to achieve.

Influence of Parasitic Capacitance on Turn-Off Current and Its Optimization Method for Transient Electromagnetic System

“…Implementing an RCD snubber circuit into the full bridge circuit can also curb the oscillation induced by stray inductance, thereby reducing the nonlinear error [13]. Reference [14] proposed a method distinct from matching damping resistors, which eliminates the oscillation by using the RC snubber circuit and pole configuration. This approach achieves the same performance as using damping resistors, without requiring the switching device to connect the damping resistor to the circuit.…”

“…At the end period of the current's falling edge, the clamping effect will eventually disappear. Consequently, for the inverter circuit equipped with a damping resistor or RC snubber, the current continues to flow through the damping resistor or RC snubber circuit, resulting in exponential decay [12][13][14][15]. For the circuit without a damping resistor or RC snubber, the current oscillates via the coil's parasitic capacitance and internal resistance [9][10][11].…”