After the primary field disappears, the induced current excited by a good conductor will not disappear instantly. The magnitude of the current is related to the conductivity of a good conductor. At the falling edge of the current pulse, a primary field will be generated, the primary field will propagate downward, and an induced current will be excited when it contacts a benign conductor. First of all, the helicopter power supply transmits a bipolar current pulse waveform to the ground through the transmitting coil. HTEM method is a time-domain electromagnetic induction detection method, and its process is divided into three stages: transmission, electromagnetic induction, and receiving data. Our work in this article provides an efficient way to improve the performance of HTEM detection systems. The experimental results further demonstrate that it achieves lower switching losses and more flexible transmission. Moreover, the switching frequency of the inverter is reduced from 10 kHz to below 100 Hz. The nine-level inverter has a peak current of 1.5 A with an adjustable turn-OFF time from 129 μs to 162 μs. Moreover, by modifying the FPGA (Field Programmable Gate Array) control program, three different turn-OFF times are achieved. Through subsequent experiments, the inverter proved to have the capability of generating trapezoidal current waveforms. The proposed inverter has adjustable turn-ON-time and turn-OFF time, which is significantly different from the conventional single-clamp inverter. ![]() ![]() In this way, the current rising edge and falling edge of this inverter are also improved effectively. Using an inverter with the proposed topology is able to avoid the complex PWM control method and switching loss. This circuit topology overcomes the shortcomings of the traditional single constant voltage clamp circuit in which the turn-OFF time is not adjustable. This article proposes a new circuit topology based on nine-level inverter technology to overcome the drawbacks of typical PWM (pulse width modulation) inverters, such as switching losses and harmonics. It should meet the concerns of low loss, high power, and fast turn-OFF time. Using the Ohm's Law, we can find the resistances of the first, second and third resistors.The current inverter is the core component of the helicopter transient electromagnetic (HTEM) detection system. There are several ways of solving this problem (see alternate solutions), but this tutorial will only go through one of these ways.īecause the resistors are connected in series, then the same current flows through each one. What is true about potential drops of resistors when connected in series?įigure 3 Example Problem, with given dataįirst, let's label the diagram with the information given in the question.How are resistors related when connected in series?.Figure 2: Example Problem: Resistors in seriesįind the total voltage supplied by the battery, and also current, voltage drop, and resistance of each resistor in the circuit. The equivalent resistance of the circuit is \(R = 30 \Omega\). The potential drops across the first, second and third resistors are, respectively: \(V = 5 V\), \(V = 8 V\) and \(V = 7 V\). The current flowing in a circuit containing four resistors connected in series is \(I = 1.0 A\). So, by Ohm's Law:Įxample of Problem on Resistors in Series Question \(\varepsilon= V = 6.0V\)) must be lost in the resistor. By conservation of energy, the potential that was gained (i.e. No energy is lost to the wires, since they are assumed to be resistance-free. The gain of potential energy occurs as a charge passes through the battery, that is, it gains a potential of \(\varepsilon = 6.0V\).
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