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Electricity
Published in Neil Petchers, Combined Heating, Cooling & Power Handbook: Technologies & Applications, 2020
The relationship of real power, apparent power, and reactive power can be understood through the trigonometric relationships of a right, or power, triangle. The power triangle consists of the following three components: VA: Volt-amperes — or apparent power — expresses power as the simple product of voltage, in volts, and current flow, in amperes, without regard to the phase relationship of the current and the voltage. A kilovolt-ampere (kVA) equals 1,000 VA.W: Watt — or true power — measures power corrected for the degree to which voltage and current are out of phase. It is the product of current times the voltage across the resistance. If voltage and current are in phase, W equals VA. If they are at all out of phase, W is less than VA. A kW equals 1,000 W.VAR: Volt-amperes reactive — imaginary or reactive power — measures the product of the voltage across and the current flowing through a reactance (inductive, capacitive, or both). It is the component of total current that is 90 degrees out of phase with voltage. Reactive power must flow from a generator, but none of this reactive power is actually expended. A kilovar (kVAR) equals 1,000 VAR.
AC Circuits Relationships
Published in Muhammad H. Rashid, Ahmad Hemami, Electricity and Electronics for Renewable Energy Technology, 2017
The power found this way is called the apparent power. This is the power that a power supply must provide for a load. The unit for measure of apparent power is VA (standing for Volt-Ampere). You may pronounce it Vee-A or say volt-amp. In conjunction with the two previously defined terms, active power and reactive power, only a part of this apparent power converts to heat and work (active power). The rest of that (reactive power) exchanges between the reactive components (inductor and/or capacitor) and the electricity source. Although the reactive power is not consumed, it must be present; that is, the source must be able to maintain it. Figure 8.29 exhibits an analogy for a better understanding of this fact. (To have the desired volume/height of water at the outlet, the reservoir must be full; that is, the volume/height below the outlet must also be provided.)
Economic Analysis of Energy Projects
Published in Moncef Krarti, Energy-Efficient Electrical Systems for Buildings, 2017
The power factor is defined as the ratio of actual power used by the consumer (expressed in kW) to the total power supplied by the utility (expressed in kVA). Figure 9.5 shows the power triangle to illustrate the concept of power factor. The reader is referred to Chapter 2 for more details on the concept of power factor. For the same actual power consumed by two customers but with different power factor values, the utility has to supply higher total power to the customer with lower power factor. To penalize customers for low power factor (generally lower than 0.85), some utilities use a power factor clause to increase the billing demand charges or to impose new charges (on total power demand or reactive power demand). For instance, the billing demand can be increased whenever the measured power factor of the customer is below a reference value or base power factor: Billeddemand=Actualdemand*(pfbasepfactual)
Design and Analysis of quasi Resonant high gain Impedance source DC-DC converter for DC microgrid
Published in International Journal of Electronics, 2023
Harinaik Sugali, Shelas Sathyan, N. J. Merlin Mary
where is the core cross-sectional area, is window area, VA volt-ampere rating, is flux density=0.2T, J is current density =3A/, is window utilization factor = 0.4 and is switching frequency. The EE25/13/7 ferrite core is selected based on area product of = 2910. The transformer turns are obtained as
Design and analysis of isolated high step-up Y-source DC/DC resonant converter for photovoltaic applications
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2023
Harinaik Sugali, Shelas Sathyan
where , is the core cross-sectional area and window area. is window utilization factor = 0.4, is flux density = 0.2T, J is current density = 3A/, VA volt-ampere rating, and is switching frequency. Based on area product value, the EE25/13/7 ferrite core is selected (available in the laboratory) having an area product of = 2910. The primary and secondary turns of the transformer are obtained as follows:
Removal of phosphorus in wastewater by sinusoidal alternating current coagulation: performance and mechanism
Published in Environmental Technology, 2022
Yihui Zhou, Shuaiqi Chen, Jingxian Qiu, Chunyou Zhu, Tao Xu, Muping Zeng, Xi He, Bonian Hu, Xueyuan Zhang, Gang Yu
A schematic diagram of phosphate removal system by SACC is shown in Figure 1. The 13 dm3 electrolytic cell was made of polymethyl methacrylate (PMMA). Ten iron plates (size: 100 × 300 mm, thickness: 2 mm) separated with five groups of parallel sacrificial anodes and cathodes were built up. The distance between any two close electrodes was 10 mm. The electrolysis that occurred on the electrode was driven by a sinusoidal alternating current (SAC) power supply (CHP-500 VA, 45–400 Hz and 0–300 V). The aeration tray was set at the bottom of the electrolytic cell. The stirring airflow rate was controlled with a valve and a rotameter. The watt-hour meter (accuracy: 0.001 kW h) was used to record the power consumption of electrolysis. Phosphorus was efficiently removed from wastewater in the electrolytic cell through a series of processes of iron dissolution, oxidation, coagulation, adsorption, complexation and precipitation.