Q: What is FACTS?
A: FACTS or flexible AC transmission system involves use of power electronic devices to ensure smooth transmission of AC power by compensating the reactive power.
Q: What is TSR?
A: TSR stands for Thyristor Switched Reactor, switching appropriate number of Inductors in capacitive lines to improve power factor
Q: Can inductance be increased?
A: Yes, by increasing the wattage of bulb from 100 W to 200 W because the inductor is used in series with it.
Q: Why is the lamp used in series with the inductor?
A: Because a standard 40 watt tube light choke cannot be directly connected to mains, hence a lamp is used in series.
Q: Which microcontroller is used in this project?
A: A 40 pin microcontroller from 8051 family is used in this project.
Q: Which inductive load is used in this project?
A: A 40 W tube choke is used in this project.
Q: Can I replace choke by induction motor?
A: Yes, one can replace the choke by induction motor.
Q: Why 100W bulb is used?
A: A 100W bulb is used to demonstrate as Linear or resistive load
Q: Can a lower wattage bulb be used?
A: Yes, inductance will decrease by using lower wattage bulb.
Q: Why are we using Fan capacitors?
A: It acts as a capacitive load.
Q: Can we see the high voltage?
A: Voltage increase may not be possible to be seen as the very place where the project is getting powered might be already having some other inductive load in that area to which the capacitive load of the project was to compensate the lagging pf. However one has to watch the voltage at the capacitor point only.
Q: What is the formula for calculating smoothing capacitor value?
A: There is some approximated formula .Peak to peak ripple voltage = Load current in amps / (2*line frequency in hertz *capacitance in farads). But as rule of thumb for 1 A current 1000uF is best. Thus it is load dependent.
Q: Why are two transformers being used?
A: One transformer is used as PT while the other is as CT. Hence 2 numbers are must. This is an academic project which is designed to understand the technology used and not designed for real time use. The load capacity is about 200 watts.
Q: How does the project calculate the number of inductors to be used?
A: The project takes into consideration the time difference between voltage and current in a capacitive circuit. A controller adds capacitors in a sequence to bring inductors onto the circuit till near unity PF is achieved. Kit is supplied with 4 capacitors and one inductor though there is provision for using 2.The controller adds capacitors in a sequence for getting increasing capacitive current in order to bring appropriate inductors onto the circuit till near unity PF is achieved. The number of inductors to come to the circuit is decided by the program till it finds the current in line with the voltage.
Q: Is the capacitor special for power factor correction or can I use any capacitor with the same rating?
A: Please note this is a project for understanding the technology and is not meant for commercial use. So we have used easily available capacitors in the market. They are fan capacitors. However one can use any type for the project as long as the capacitance and voltage rating are met. But the real PF correction capacitors are different.
Q: How did you calculate the value of capacitor connected parallel with the load?
A: The value of capacitor coming into the circuit is decided by the program. We had taken some arbitrary value of 2.2uF (C) by trial, apparently adequate enough to compensate the PF developed by the simple inductor used. The total capacitance value goes on increasing by C or C+C or C+C+C or C+C+C+C as the inductive current goes on increasing. One can increase the inductive current by changing the wattage of the lamp which is used in series with the inductor. For example a 15 watt lamp will produce too little a lagging current while a 100 watt can result in much higher inductive current.
Q: What is the advantage of using TSR to reduce Ferranti effect?
A: It is a solid state device that switches inductors on zero voltage crossing of the waveform over electro-mechanical type that is prone to contact pitting.
Q: As the no. of components increase how can you justify the decrease in cost?
A: Being solid state, maintenance cost is low and thus decrease in cost is justified.
Q: How is micro controller used to control voltage?
A: Microcontroller is not controlling the voltage. It only provides trigger pulses to the thyristors through opto-couplers for switching on the reactors as and when required while fixed capacitive loading is available on the 220 volt line.
Q: Why only back to back thyristors are used?
A: One triac could have been used in place of a pair back to back SCRs but in real world use, triacs have many limitations in terms of technical and commercial use. Triacs are available for low voltage and low current applications (Max800v /25A) while SCRs are available in much more higher ratings of kilo volts and kilo amps. Besides the same the triac requires higher gate current in 2nd and 4th quadrant as against 1st and 3rd, while compared against SCR whose uniform gate current requirement is 100 times less.
Q: Any disadvantages of this project?
A: Yes, SCRs are prone to damage by lightning strikes on the transmission lines.