Power Factor
Power factor is a term which explains how efficiently electrical power is consumed. As we have to pay for the total electrical power.
In another terms, Power factor is cosine angle in between voltage & current ! Power factor is very important term in electrical field, It must be controlled at any cost.
There are basically, three types of electrical loads :
- Resistive load
- Inductive load
- Capacitive load
- Resistive loads have negligible impact on power factor.
- Electrical current get lagging across inductive loads
- Electrical current get leading in capacitive loads.
- Both Inductive & capacitive loads are counter to each other.
Maximum industrial load is inductive, To balance that inductive load, Capacitor banks are been installed.
Controlling the Power factor is like balancing the weighing scale on both sides. One side inductive load While another side Capacitive load. Capacitor banks come into the circuit according to load so that a balance must be maintained in Inductive & Capacitive load.
This control of capacitors are done with the help of automatic power factor controller. Power factor controller continuously monitors running Power factor & compare the running value with set value. After that Controller gives command through relay to control the ON-OFF switching of Capacitors through Contactors.
In this post, We are going to discuss Schneider Electric make Automatic power factor controller Varlogic RT12.
But first ;
Why APFC Controller Is Required?
-
Avoid PF penalty
-
Reduce current
-
Improve system efficiency
-
Better voltage regulation
Schneider Electric’s Varlogic RT-12 APFC
|
|
- When running load is capacitive in nature; RT shows over-compensation with the help of indication LED.
- When all the 12 steps of RT are On but still power factor is low than insufficient compensation LED glows.
Varlogic RT-12 Specifications
- SET, UP & DOWN buttons are provided on the controller so that we can easily change the Parameter’s Setting.
SET, UP & DOWN BUTTONS
- Display is 7 segments, 4 digits. For Big values Kilo & Mega LEDs are present at the side of display.
|
|
- This controller is equipped with 12 relays whose present status can be displayed through 12 LEDs As shown in an image below. (Which we can say capacitor Steps)
- Relays contact rating is 3Amps/250VAC.
|
|
- Over voltage, Over Compensation & Insufficient compensation alarm LEDs are present on front.
- RT also displays the RMS value of Voltage, current, Active power(kW), Reactive Power(KVAR) & Apparent power(kVA).
- The status of RT whether it is in ‘Normal state’ or ‘Capacitor is increasing’ or ‘Capacitor is decreasing’. All the three status are shown with three LEDs As shown in an image below.
- There is one special ‘alarm relay’ is provided so that some type of buzzer can be connected. This Alarm relay operates after 1 minute in insufficient compensation & over compensation states.
|
|
Connection Diagram for Varlogic RT-12
|
|
- RT12 Auxiliary Voltage is 400Volts. Yellow & Blue phases should be connected to controller through 2Amps fuses or MCB.
- CT coils up to 10000/5 can be connected. CT coil should be installed on remaining Red phase. CT coil should be of good quality because it is the main part which sensing load current.
- An Isolated transformer 400/230 volts is used for capacitors steps. The 400 volt Supply which is connected to RT12; parallelly be given to transformer primary.
- On Secondary side Transformer’s neutral is directly connected to all the contactors & phase is connected to common point of RT. This common point of RT connected to all the relays commonly internally.
Controls & Menu Operation of Varlogic RT-12
- If we want to ‘set the parameter’ than we have to enter menu option by pressing set button for 3 sec. After than we can go through all the options by UP & Down buttons & Then select the option with set button & change the parameters with up & Down buttons. Enter the selected parameter with set button.
- If we want to ‘see the running value’ of power factor, voltage, Power & current etc. We just need to press UP& Down buttons. (Selected options are shown on Display & indicated with side panel LEDs.)
- When RON is selected RT is in Auto mode. In Auto mode, Auto/Man. LED glows continuously.
- When ROFF is selected RT is in Manual mode. In Manual mode, Auto/Man. LED blinks. In manual mode if no button is pressed under 5 minutes it automatically shifts to auto mode.
Present Voltage of the system can be seen by just selecting this LED using UP & Down buttons, No need to enter menu option.
FAQs related to APFC controller
Q1. What is an APFC controller?
An APFC controller automatically maintains the power factor by switching capacitor banks based on system load.
Q2. What is the function of Schneider Varlogic RT-12?
It controls up to 12 capacitor steps and maintains the desired power factor automatically.
Q3. What happens if power factor is low?
Low power factor increases current, causes losses, voltage drop, and may lead to electricity penalty.
Q4. What is C/k value in APFC?
C/k is the ratio of first capacitor kVAR to CT ratio. It determines the switching sensitivity of capacitor steps.
Q5. What is the ideal power factor setting?
Generally, 0.95 to 0.99 lagging is recommended for industrial systems.
Summary
- Varlogic RT 12 is overall a very good Automatic power factor controller. All the values whether it is CT ratio value, cos(phi) value, step value- all the values can be seen & changed easily.
- It continuously indicate the status of RT whether it is increasing capacitor or decreasing capacitor or in normal stable condition.
- It also indicate about Over compensation & Insufficient compensation states.
- It also equipped with over Voltage protection.
- 1 special alarm relay is being provided.
EVERYTHING IS WELL EXPLAINED, GOOD JOB !
Thank you brother for this post. It help me alot to understand this product.
Thank for the comment,Sir!