Study On High-power Bipolar Steep Pulse Source

In transient detection field, the quality and performance of excitation source willdirectly affect the detection signal of geological bodies, it needs the pulse currentsource of the linear reversal edge, the short delay reversal, the constant load currentvalue and the good consistency of positive and negative. In the ideal case the excitationsource is the bipolarity rectangular square-wave, but due to the load of the largeinductance coil, it is very difficult to realize the ideal bipolarity rectangularsquare-wave.At present, the front edge of the bipolar pulse current waveform ofemission is exponentially increasing, and the back edge is the slanting wave, theconventional transient electromagnetic method uses only the back edge response, andgets low efficiency. Meanwhile, the transmitter, which is generally powered by abattery, causes low voltage and power and is also not conducive to wild high powerdetection operations.To solve the mentioned problem, this paper studies the circuit topology andcontrol method of the improvement of impulse shape of emission current and designsthe bipolar pulse current source circuit to improve the stability of the emission currentpulse waveform and the risiong-falling edge linearity; This paper also studies theclamp voltage source based on pulse sequence control to provide a stable clampingvoltage for the rising-falling edge of the current waveform. By the way, the paperdesigns synchronous generator rectifier power supply to meet the requirements of thefired power electromagnetic probe.At first, this paper analyzes the research status, the problems and developmenttendency of the transient electromagnetic launch technology at home and abroad,analyzes the key issues of affecting the bipolar pulse current source waveform. Abipolar pulse current source, which lifts front slope, has the same linear front and backedge, the stable load current, is proposed based on the analysis of the advantages anddisadvantages of the existing transmitter circuit topology.Secondly, the existing transmitter circuit topology and control method has beenimproved. This paper designs the main circuit of high power bipolar steep pulsecurrent source which uses constant current source policy with front-rear clampingstrategy to achieve the rapid linearthe rising-falling and to reduce the number ofswitches and costs. It improves the reliability of the circuit and reduces the power consumption. Then this paper studies on the simulation and experiment to analyze theemission current waveform and verify the feasibility and peformance of the maincircuit topology.In order to maintain the stable clamping capacitor voltage, design the constantclamping voltage source based on the pulse sequence control technology, andsuccessfully applied to bipolar pulse current source, provide the constant clampingvoltage for the load current. The simulation results show that the voltage source hasdynamic response speed、good transient characteristics and provides stable clampingvoltage for the rising-falling edge of the load current when it’s unstable.At last, in order to meet the demand of wild long time experiment and high powertransmitter, this paper designs the power supply based on the synchronous generator.Excitation control system with double closed-loop control strategy, provides a stablevoltage when the power supply charges the capacitor, suddenly adds a load, loadchanges, and stable and adjustable DC voltage for the steep pulse current source.