# automatic power factor controller using microcontroller

Posted on Feb 6, 2014

The 230 V, 50 Hz is step downed using voltage transformer and current transformer is used to extract the waveforms of current. The output of the voltage transformer is proportional to the voltage across the load and output of current transformer is proportional to the currentG‚throughG‚the load. These waveforms are fed to Voltage Comparators const

ructedG‚usingG‚LM358G‚op-amp. Since it is a zero crossing detector, its outputG‚changesG‚during zero crossing of the current and voltage waveforms. These outputs are fed to the PIC which does the further power factor calculations. PIC 16F877A microcontroller is the heart of this Automatic Power Factor Controller, it find, displays andG‚controlsG‚the Power Factor. To correct power factor, first we need to find the current power factor. It can be find by taking tangent of ratio of time between zero crossing of current and voltageG‚waveformsG‚and two successive zero crossing of voltage waveform. Then it displays the calculated power factor in the 16G—2 LCD Display andG‚switchesG‚ON the capacitors if required. When load is connected the power factor is calculated by the PIC microcontroller. If the calculated power factor is less than 0. 9 then the relay switches on the capacitor. The relays are switched using ULN2003 which is basically a driver IC. ULN2003 consists of seven DARLINGTON PAIRS. The current lead in capacitor compensates the corresponding current lag which is usually present in loads. Hence the phase difference between the current and voltage will be reduced. Power Factor Correcting capacitor connected parallel to load through relay, if the relay is energized by microcontroller it will connect G‚the capacitor parallel with load, if relay deenergized it will remove the capacitor from the load. When the resistive load...

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