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5 Grounding and Bonding
Published in C. Sankaran, Power Quality, 2017
In Chapter 1, a ground loop was defined as a potentially detrimental loop formed when two or more points in an electrical system that are normally at ground potential are connected by a conducting path such that either or both points are not at the same potential. Let’s examine the circuit shown in Figure 5.12. Here, the ground plane is at different potentials for the two devices that share the ground circuit. This sets up circulation of currents in the loop formed between the two devices by the common ground wires and the signal ground conductor. Such an occurrence can result in performance degradation or damage to devices within the loop. Ground loops are the result of faulty or improper facility wiring practices that cause stray currents to flow in the ground path, creating a voltage differential between two points in the ground system. They may also be due to a high-resistance or high-impedance connection between a device and the ground plane. Because the signal common or ground conductor is a low-impedance connection, it only takes a low-level ground loop potential to cause significant current to flow in the loop. By adhering to sound ground and bonding practices, as discussed throughout this chapter, ground loop potentials can be minimized or eliminated.
Facility Grounding
Published in Jerry C. Whitaker, Electronic Systems Maintenance Handbook, 2017
The AC line ground connection for individual pieces of equipment often presents a built-in problem for the system designer. If the equipment is grounded through the chassis to the equipment-room ground point, a ground loop can be created through the green-wire ground connection when the equipment is plugged in. The solution to this problem involves careful design and installation of the AC powerdistribution system to minimize ground-loop currents, while at the same time providing the required protection against ground faults. Some equipment manufacturers provide a convenient solution to the ground-loop problem by isolating the signal ground from the AC and chassis ground. This feature offers the user the best of both worlds: the ability to create a signal ground system and AC ground system that are essentially free of interaction and ground loops. Do not confuse this isolated signal ground with the isolated ground system described in the section entitled “Noise Control.” In this context, “isolated” refers only to the equipment input/output (signal) connections, not the equipment chassis; there is still only one integrated ground system for the facility, and all equipment is tied to it.
Noise and artefacts
Published in Kumar Shrawan, Mital Anil, Electromyography in Ergonomics, 2017
A complement to shielding is grounding. The purpose of grounding is to connect all metal objects in the environment to the common ground so that they will obtain the same potential. In this way there will be no voltage difference between the subject and the various objects and, thus, no electric field that can cause interference, nor for that matter, any currents through the subject’s body. Potential differences can be caused by, for example, stray currents in conducting pipes, ground currents in unsymmetrically loaded three-phase power systems, and currents induced in ground loops. In a measurement system consisting of pre-amplifiers, connecting cables, amplifiers, filters, RMS-DC converters, and analog-to-digital converters, etc., it is important to control the ground currents both from the disturbance and the safety point of view. It is difficult to separate a signal ground, a supply ground, and a protective ground. Since a supply ground may carry leakage currents from transformers, power line wires, and cables, it is advisable to use differential amplifier inputs in all units receiving input signals of low amplitude. Ground loops must be avoided, but to do that may require that protective ground is disconnected from all units but one and oversized ground wires between the units are used instead. If this solution cannot be permitted for safety reasons, depending of how the system is built together, it will be necessary to use isolation amplifiers between the subject and the equipment.
Design and implementation of a versatile H-bridge power supply for experiments on the STOR-M Tokamak
Published in Radiation Effects and Defects in Solids, 2023
H. Bsharat, M. Patterson, C. Xiao
The timing signals that control the gate drivers come from a Mercury Development Board (Model ME1B-200M) utilizing a Xilinx Spartan-3A FPGA. The TTL (Transistor-Transistor Logic) output voltage pulses are converted to optical signal using optical emitters (2521 HFBR). The scripting that describes the timing was coded in VHDL (Very-high-speed-integrated-circuit Hardware Description Language). The digital control system allows for rapid and accurate tuning of the gate signals to be adjusted for the resonant frequencies of different loads, and easy modification of RMP pulse length. The timing of the start of the sinusoidal waveform is provided by the STOR-M master control system, also through an optical trigger signal. Figure 5 shows the flow of FPGA timing control and the fiber optical links for floating the circuits and breaking ground loops.
Effects of noises on curve fitting to the I–V characteristics of retarding filed analyzers
Published in Radiation Effects and Defects in Solids, 2020
C. Y. Sun, Y. L. Li, I. Voldiner, L. Pan, N. Yan, H. Zhang, C. Xiao
The RFA entrance slits are biased negatively at −180 V and the grid 1 voltage is scanned from −100 V to 100 V at a frequency of 300 Hz to selectively allow part of ions in the velocity distribution to pass the grid. Grid 2 is biased negatively at −180 V to reflect secondary electron emission from the collector or from Grid 1. The DC bias voltage is provided by the 9 V battery packs connected in series. The scanning voltage is produced by a waveform generator programmable via remote desk control through an internet connection. The waveforms used are either triangular or sinusoidal in the experiments. Although the waveform generator stays on all the time, the data are collected starting shortly before the discharges. The collector is connected to the chamber wall through a current-to-voltage conversion resistor. The details about the circuits can be found in Ref. (11). The coaxial cable bundle connecting the RFA head to the power supplies and the data acquisition system is about 5 m. All signals from the RFA circuit go through optoelectronic isolators before being connected to the data acquisition system. The digitizers are 12 bits and the sampling rate is 1 M/s. The system is grounded as a single point on the chamber without ground loops.
Finite element simulation of self-heated pavement under different mechanical and thermal loading conditions
Published in Road Materials and Pavement Design, 2019
Xin He, Sherif Abdelaziz, Fangliang Chen, Huiming Yin
To overcome the high material costs and construction challenges associated with the Dutch system, this paper proposes to bury the loops in the base layer beneath the surface layer as shown in Figure 1(b), rather than embedding the loops directly within the thin asphalt layer. It is applicable for aggregate or concrete bases alike. Placing the pavement loops in the base layer allows the use of standard, inexpensive thin asphalt layers without special construction precautions to limit asphalt cracks. Also, by burying the loops in the base layer, the stress on the loops applied by traffic loads would be reduced as the base cover at top of the loops would take some loads. Based on this consideration, a more compliant and cheaper material can be used to make the loops. The proposed self-heated pavement technique consists of, as shown in Figure 1(c): (1) pavement loops installed in the pavement base layer, (2) geothermal ground loops installed at the highway sides, (3) circulation pumps to circulate a geothermal fluid between the pavement and ground loops, and (4) a solar system for pump operation including photovoltaic solar panels, converters, batteries to store the electricity generated during the day for use at night, and controllers to manage the system operation. Similar technology has been used in buildings (Chen, He, & Yin, 2016; Yin, Yang, Kelly, & Garant, 2013). The use of a solar system to operate the circulation pumps extends the applicability of the technique to US highways in remote areas faraway from electrical sources.