10-08-2011, 12:48 PM
Presented By:
Rahul Ranjan
Rahul Srivastava
Ravi Shankar Patel
Rishu Raj Singh
Shashi Bhushan
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AUTOMATIC POWER FACTOR CONTROLLER CUM RECTIFIER
Project Aim
This project discusses the need for power factor correction and provided a suitable do-it-yourself (DIY) solution that could be used for small-scale industries and establishments.
In small industrial units where the load is contributed by a number of inductive appliances, it is cumbersome to switch in capacitor banks at the power entry point in accordance with the varying load to neutralize the inductive reactance of the load.
NEED FOR AUTOMATIC POWER FACTOR CORRECTION
varying power demand on the supply system.
power factor also varies as a function of the load requirements.
difficult to maintain a consistent power factor by use of Fixed Compensation i.e. fixed capacitors.
leading power factor under light load conditions(fixed compensation)
This result in over voltages, saturation of transformers, mal-operation of diesel generating sets, penalties by electric supply authorities.
automatically variation, without manual intervention, the compensation to suit the load requirements.
Automatic Power Factor Correction(APFC) system provide this facility.
leading power factor will be also prevented.
Power Factor Correction
What is power factor…?
Power Factor = Active Power (kW)/Apparent Power (kVA
PF≤1.0
Usually P.F is always “Lag” (Inductive)
Some time P.F can be “Lead” (Capacitive).
How does it Work?
As the power factor drops, the system becomes less efficient
A drop from from unity to 0.9 in the power factor results in 15 per cent more current requirement for the same load.
Power factor of 0.5 requires approximately 100 per cent (twice as much ) more current to feed the same load.
Industrial loads are inductive in nature, wherein the current lags the applied voltage and their power factor is termed as lagging power factor.
The objective therefore should be to neutralize the lagging power factor of inductive loads by using switching capacitors across the load, which have a leading power factor
An APFCU / FAPFCU works by constantly monitoring the load on a facility and connecting or disconnecting capacitive kVAr in order to maintain a preset target power factor.
The brain of an APFCU / FAPFCU is the controller
It receives the plant load information from a current transformer which is located on the main bus bar,
POWER FACTOR CORRECTION METHOD
Method:1
If we access to a power meter whose power reading is true.
we can compare with the calculated apparent power (obtained by multiplying the line voltage and current into the load ).
we can easily determine the reactive power and power factor from these values of true and apparent power.
Method :2
.This method is specifically useful for finding the proper capacitor kVAR value for single- / three- phase induction motors.
when the motor’s horsepower (HP) and its full-load power factor and motor efficiency are known. The kVAR required to correct the PF can be found as.
kVAR = (K1-K2)×HP×0.746
Efficiency
Where ‘HP’ is the motor’s name –plate horsepower.
‘Efficiency’ is the motor’s full- load efficiency
expressed as a percentage, ‘K1’ is a factor (from Table I) corresponding to the existing PF at full load .
‘K2’ is a factor (from Table II) for the desired PF after correction.
Benefits of APFC
Consistently high power factor under fluctuating loads
Prevention of leading power factor
Eliminate power factor penalty
Lower energy consumption by reducing losses
Continuously sense and monitor load
Automatically switch on/off relevant capacitors steps for consistent power factor
Ensures easy user interface
Protect under any internal fault
Advance µ- relay with communication facility
Used MPP-H/MD-XL/FF(APP) type capacitors
User friendly, aesthetecally designed enclosure, dust and vermin proof.
