To learn about the power factor measurement, you should have a basic knowledge of power factor. There are three types of loads.
- Resistive
- Inductive
- Capacitive
When we apply AC voltage to resistive loads it will not change the current wave form. But inductive loads will force to lag the current waveform and in the case of capacitive loading it will force to lead the current waveform than voltage waveform.
You can see the waveforms of inductive load. The phase shift of 30 degree is present in the current waveform.
The power factor is basically the “angle cosine of that lagging current”. In simple words, current is lagging by voltage with some angle and if we take the cosine of that angle we will get power factor.
Zero Cross Detection:
Zero cross detection is a method which can enable us to measure the time between voltage and current. In this technique we g
1.AC Voltage Measurement Using Atmel AVR Microcontroller
2. AC Current Measurement Using Atmel AVR Microcontroller
Now comeback to the zero crossing method, you can see that we set the reference value of zero volts at non – inverting pin (+) of both amplifiers. So, according to comparator action it will give us high value (1) at the output whenever a zero will cross in the waveform. The output of comparators is shown below in the figure in which yellow is the output of voltage and blue is the output of current having some lag.
et a high value (i.e. 1) whenever a zero will cross the system. There are many ways to implement it. But remember, this technique is the heart of this project so implementation must be accurate. In this project we implemented zero crossing using LM358 an 8 pin IC having dual amplifiers in it. In zero crossing, we have to get a “high” value during crossing of zero in waveforms. So to get that value we use amplifier as a comparator which will compare the non inverting reference value and then act accordingly.
We will use a 16×2 LCD to show our results and ATmega 8 or ATmega16 can be used for the project. In the simulation, take upper sine generator as output of Potential Transformer (PT) and lower sine generator as output of Current Transformer (CT). The reason behind using CT and PT is, we cannot give high voltage to the IC LM358. It will burn the IC badly. So first step down the voltage and step down the current at such extent that the highest peak of current and voltage is not more than 5V. If you have no idea of using CT and PT in the real systems then see the links below.
1.AC Voltage Measurement Using Atmel AVR Microcontroller
2. AC Current Measurement Using Atmel AVR Microcontroller
Now comeback to the zero crossing method, you can see that we set the reference value of zero volts at non – inverting pin (+) of both amplifiers. So, according to comparator action it will give us high value (1) at the output whenever a zero will cross in the waveform. The output of comparators is shown below in the figure in which yellow is the output of voltage and blue is the output of current having some lag.
Read More: Power factor measurement using Atmel AVR Micro-Controllers