China
Africa
Explore chapters and articles related to this topic
AC Circuits Relationships
Published in Muhammad H. Rashid, Ahmad Hemami, Electricity and Electronics for Renewable Energy Technology, 2017
It can be followed from Figure 8.12 that the current through an inductor has an inverse effect with the frequency of the AC line. The effect of the insertion of an inductor in an AC circuit is exhibited in the form of impedance to the current, but because it is not a resistance (with ohm value that can be measured), it is called reactance. So, reactance in an AC circuit is what exhibits a resistance to the flow of current, but it is not because of a resistive element that converts the electrical energy to heat. Reactance is measured in ohms. To specify that reactance is due to an inductor, when necessary, it is more particularly addressed as inductive reactance. The reactance of an inductor, denoted by XL, depends on the frequency and the inductance, and can be found from XL=2πfL where π is a constant (π = 3.14159265), f is the frequency of the AC electricity measured in Hz, and L is the inductance measured in henries (see Section 4.10).
Series alternating-current circuits
Published in Adrian Waygood, An Introduction to Electrical Science, 2013
From: XL=2πfLandXC=12πfC . .. we know that the inductive reactance of a circuit is directly proportional to the supply frequency whereas the capacitive reactance is inversely proportional to the supply frequency. So, if we gradually inc rease the supply frequency, the inductive reactance will gradually increase, while the capacitive reactance will decrease.
Electricity
Published in Neil Petchers, Combined Heating, Cooling & Power Handbook: Technologies & Applications, 2020
Capacitive reactance depends on rate of voltage change, in volts per second. Like inductive reactance, capacitive reactance is affected by frequency and tends to limit the magnitude of current flow. That is, the greater the capacitive reactance, the lower the magnitude of current flow. The critical difference is that while inductive reactance is directly proportional to frequency, capacitive reactance is inversely proportional to frequency. If frequency is increased, the value of capacitive reactance is reduced. For example, if the frequency in an ac circuit containing capacitive reactance is increased from 50 Hz to 60 Hz, the magnitude of current flow will increase by 120% of the 50 Hz value.
Dielectric Thermoscopy Characterization of Water Contaminated Grease
Published in Tribology Transactions, 2018
Nicholas Dittes, Anders Pettersson, Pär Marklund, Defeng Lang, Piet M. Lugt
There is more than one physical property that contributes to the functionality of this measurement. Research shows that the dielectric constant of water rises rapidly as the frequency of measurement becomes lower (Angulo-Sherman and Mercado-Uribe (25)). This is due to two properties of water: the first results from the ability of water to separate into ion pairs that can move toward the charged electrodes, decreasing reactance and increasing capacitance. Reactance is the imaginary part of impedance, meaning that a smaller magnitude capacitive reactance results in a higher opposition of the capacitor to a change in voltage or current. The ions increase ionic conduction, allowing electrons to move more easily and, additionally, with a lower frequency the ion pairs can separate farther resulting in more stored energy (“Ion Association” (26)). The second involves the dipole pairs of water molecules that polarize according to the direction of the electric field (Lewowski (23)). This happens only with low frequencies (in the range of tens or hundreds of Hertz, not megahertz or higher) because there is a greater time between alternating electric fields, thus allowing for a charge to be stored in either polarized dipoles or ion pairs due to it being a “slow” process (Trout and Parrinello (22)). Normally, dielectric properties are measured at frequencies above 1 MHz (i.e., radio frequency–based techniques) to reduce the mentioned increases in dielectric constant but are more complicated than low-frequency measurements (Dean, et al. (20)). In other words, more typical dielectric measurements use high frequencies (in the range of megahertz to gigahertz), so the contribution to the impedance of the measurement from ionic conduction is less than that of the impedance due to the capacitance (Lewowski (23); Bonanos, et al. (27); Flaschke and Trankler (28)).