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Improved power quality and productivity in an iron ore mine by
Improved power quality and productivity in an iron ore mine by

... −− Closed loop control, based on power factor control, Mvar control or voltage control on the 6.3 kV bus; − − Open loop reactive power control. Operating experiences The main goal of the SVC installation is to reduce voltage variations on the 6.3 kV and 145 kV bus bars. A comparison between the volt ...
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... Figure 1.36 (a) is a single-diode clipper circuit. The diode D1 is off as long as VI < VB + V . With D1 off, the current is approximately zero, the voltage drop across R is essentially zero, and the output voltage follows the input voltage. When VI > VB + V , the diode turns on, the output voltage ...
Long Lifetime DC-Link Voltage Stabilization Module for Smart Grid Application  Huai Wang
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... reactive shunt compensation. The purpose of this models, to eliminate time-varying inductances by reactive compensation is to change the natural referring the stator and rotor quantities to a fixed or electrical characteristics of the transmission line to rotating reference frame. On an overall cost ...
RFVC1824 数据资料DataSheet下载
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... power of 12dBm from a 3V supply. Phase noise is -106dBc/Hz at 100kHz offset. The RFVC1824 is avalable in a low cost leadless ceramic 4mm x 4mm surface mount QFN outline. ...
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... where: Vd = V+ – V– (differential voltage) Vcm= ½( V+ + V– ) (common mode voltage) ...
Differential power algorithm based maximum power point tracking
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... The kilowatt-hours (kWh) to a customer is measured with a kWh meter corresponding to the average power consumed over a period of time. The cost/rate of the kWh may very depending on when the power is used (high vs. low demand) and how much total power has been consumed (cost may go down after so man ...
DIY Kit189. 120 Second Voice Recorder Module
DIY Kit189. 120 Second Voice Recorder Module

... depending on the chip. The sampling frequency of each chip can also be adjusted from 4 kHz to 12 kHz with an external resistor, giving greater flexibility in duration versus recording quality. Recordings are stored in on-chip Flash memory, providing non-volatile storage when power is removed. The au ...
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... Load regulation of a FPS is provided by the use of a shunt magnetic path which has an air gap between it and the main EI lamination. The air gap is used to limit the flux in the shunt portion of the FPS and therefore preventing the magnetic saturation. In short it forms a "closed loop" whereby the f ...
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... depending on the chip. The sampling frequency of each chip can also be adjusted from 4 kHz to 12 kHz with an external resistor, giving greater flexibility in duration versus recording quality. Recordings are stored in on-chip Flash memory, providing non-volatile storage when power is removed. The au ...
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... $600 cost savings using a 750 VA buck-boost transformer over a 7,500 VA distribution transformer. Some larger tanning beds require 3 phase power, so using two transformers in the same example above will save the customer approximately $1200.00 and a lot of floor space. Multiply this by the number of ...
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Types of DR Island Systems - IEEE Standards working groups

...  May require load control and/or the ability to parallel multiple generators before load connection  Could have systems that carry through on grid fail, but cannot perform a cold load pickup  Turbines have little peak capability.  Recip machines typically will not do more than 100% because of tu ...
Sample Study Material
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... In Frequency Modulation (FM) the instantaneous value of the information signal controls the frequency of the carrier wave. This is illustrated in the following diagrams. Notice that as the amplitude of the information signal increases above 0 volts, the frequency of the carrier increases, and as the ...
< 1 ... 908 909 910 911 912 913 914 915 916 ... 1202 >

Pulse-width modulation



Pulse-width modulation (PWM), or pulse-duration modulation (PDM), is a modulation technique used to encode a message into a pulsing signal. Although this modulation technique can be used to encode information for transmission, its main use is to allow the control of the power supplied to electrical devices, especially to inertial loads such as motors. In addition, PWM is one of the two principal algorithms used in photovoltaic solar battery chargers, the other being MPPT.The average value of voltage (and current) fed to the load is controlled by turning the switch between supply and load on and off at a fast rate. The longer the switch is on compared to the off periods, the higher the total power supplied to the load.The PWM switching frequency has to be much higher than what would affect the load (the device that uses the power), which is to say that the resultant waveform perceived by the load must be as smooth as possible. Typically switching has to be done several times a minute in an electric stove, 120 Hz in a lamp dimmer, from few kilohertz (kHz) to tens of kHz for a motor drive and well into the tens or hundreds of kHz in audio amplifiers and computer power supplies.The term duty cycle describes the proportion of 'on' time to the regular interval or 'period' of time; a low duty cycle corresponds to low power, because the power is off for most of the time. Duty cycle is expressed in percent, 100% being fully on.The main advantage of PWM is that power loss in the switching devices is very low. When a switch is off there is practically no current, and when it is on and power is being transferred to the load, there is almost no voltage drop across the switch. Power loss, being the product of voltage and current, is thus in both cases close to zero. PWM also works well with digital controls, which, because of their on/off nature, can easily set the needed duty cycle.PWM has also been used in certain communication systems where its duty cycle has been used to convey information over a communications channel.
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