Explore chapters and articles related to this topic
Essentials of Electricity
Published in Anthony J. Pansini, Guide to Electrical Power Distribution Systems, 2020
While the basic units used in the measurement of electrical quantities are the ohm, volt, ampere, and watt, these units often appear in such large quantities that it would be inconvenient to speak in terms of the basic unit. For example, approximately 6 volts may be obtained from a storage battery, and 117 volts from a house electrical receptacle. However, when discussing high-voltage transformers and transmission lines terms of 10,000 V, 50,000 V, and sometimes voltage in excess of 100,000 V are used. To simplify this, the prefix “kilo” is generally used for large quantities. This indicates that the number should be multiplied by 1000. Thus, a 10-kilovolt (kV) transformer is rated as being capable of handling 10,000 V; similarly, 60 kV, 60 kW, and so on. In general notation, abbreviate kilo and simply refer to “k,” hence, kV, kW, and so on.
Instrumentation and Measurement
Published in Dale R. Patrick, Stephen W. Fardo, Ray E. Richardson, Brian W. Fardo, Energy Conservation Guidebook, 2020
Dale R. Patrick, Stephen W. Fardo, Ray E. Richardson, Brian W. Fardo
The amount of electrical energy that a building uses during operation is constantly monitored by a watt-hour meter. This instrument responds to the amount of voltage and current that is delivered to the system to do work. Since power is expressed as voltage times current, we can describe electric energy as amount of power used for a given period of time. Watt-hours (Wh) and kilowatt hours (kWh) are common measures of electrical energy. The prefix “kilo” of one term is a metric expression denoting 1000. The electrical utility company determines power consumption by kilowatt hour values.
Introduction
Published in Ronald L. Fournier, Basic Transport Phenomena in Biomedical Engineering, 2017
Oftentimes, a particular unit is expressed as a multiple or a decimal fraction. For example, 1/1000th of a meter is known as a millimeter, where the prefix “milli-” means to multiply the base unit of meter by the factor of 10−3. The prefix “kilo-” means to multiply the base unit by 1000. So, a kilogram is the same as 1000 grams. Table 1.4 summarizes a variety of prefixes that are commonly used to scale a base unit.
Feasibility investigation regarding evaluation of external wall-thickness loss in nonmagnetic tubes using a bobbin-typed electromagnetic acoustic transducer
Published in Research in Nondestructive Evaluation, 2019
Yong Li, Bei Yan, Haoqing Jing, Yi Wang, Jinhua Hu, Zhenmao Chen
In a bid to predict the signal responses from the proposed EMAT probe to EWL, simulations are needed. Until now, Finite Element Modeling (FEM) has been prevalent for EMAT simulations [10]. Whereas, it is prone to considerably high computation burden, and thus give rise to time-consuming simulations. This is because the frequency of the excitation current is normally over hundreds of kilo-hertz. As a result, extremely dense mesh should be applied when discretizing the conductor region if proper solutions particularly to electromagnetic problems are pursued. Besides, although analytical models for fast solutions to the electromagnetic quantities have been proposed for EMAT simulations, in order for model simplification, parameters of the magnet are barely taken into account, and the static magnetic field is assumed to be homogeneous within the solution region [11]. The modeling treatment and assumption leave the prediction of EMAT signals vulnerable to loss in computation accuracy. Consequently, a better model is still demanded for efficient simulations with the bobbin-typed EMAT probe.
A Lead-Free Spiral Bimorph Piezoelectric MEMS Energy Harvester for Enhanced Power Density
Published in IETE Technical Review, 2021
Vicky Butram, Ashutosh Mishra, Alok Naugarhiya
Various energy sources like solar, vibration, radio frequency and thermal are suitable candidates for energy harvesting methods [7]. Out of these, vibrations are readily available in the environment which is directly converted into the electrical energy. Within the Micro-Electromechanical System (MEMS)-based vibration energy harvester space, piezoelectric transducers are mostly preferred over electrostatic and electromagnetic generators [8–10]. Piezo-MEMS-based energy harvester is a promising approach to develop an on-board power source grown over the silicon substrate. These energy harvesters are compact and cost-effective for scavenging electrical energy from a low level of vibrations present in the environment [11–14]. The most common structure for piezoelectric energy harvesters is cantilever beam subjected to vibratory excitation. There exist an optimum damping and resonant frequency of harvester at which the maximum electrical energy is extracted from vibration [15]. Typical cantilever of dimension less than 1 inch exhibits resonant frequency in order of kilo hertz. It is quite higher than normally available ambient vibration frequency (<200 Hz). A slight deviation in the harvester’s resonant frequency from the vibration frequency leads to a significant drop in extracted power. Therefore, in order to maximize output power, the harvester should maintain on-resonance condition. The cantilever beam subject to a loading has natural frequency inversely proportional to the length [16]. Therefore, a trade-off between the length and frequency is developed for designing harvester with low active area. Hence, designing such harvesters at micro-scale dimension of less than 200 Hz is a challenging task.