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International Electrical Engineering Journal (IEEJ) Vol. 5 (2014) No.7, pp. 1484-1489
International Electrical Engineering Journal (IEEJ) Vol. 5 (2014) No.7, pp. 1484-1489

... varying analog signals; this PWM conversion generally has a very high electrical efficiency [3]. In controlling either a three phase synchronous motor or a three phase induction motor it is desirable to receive a perfectly sinusoidal current waveform in motor windings, with relative phase displaceme ...
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... products are ideally suited for controlling the output of brushless excited synchronous generators up to 5MW. These devices offer higher powered output and accept a variety of accessory items for new and retrofit applications where high performance and reliability are mandatory. These devices utiliz ...
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... coupled across to the secondary winding. These high frequency harmonics on the secondary winding are difficult to suppress. Even with an output filter inductor, the high frequency harmonics pass through the filter inductor to the output via the inductor’s parasitic capacitance. The best solution fo ...
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... switching pulses can be generated during one fundamental period, which results in a switching frequency to fundamental frequency ratio of 3-4. Therefore, PWM cannot provide acceptable results. The final goal is to run the introduced system with a current THD of less than 5% without the use of an add ...
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... and explained through an average behavioral model and state-plane analysis. The operation of the controller is experimentally verified on a 12W 12V-to-1.5V converter, demonstrating voltage-mode control operation as well as time-optimal response for load transients. Existing system:  In recent years ...
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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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