The project is designed to minimize penalty for industrial units by using automatic power factor correction unit. Power factor is defined as the ratio of real power to apparent power. This definition is often mathematically represented as KW/KVA, where the numerator is the active (real) power and the denominator is the (active + reactive) or apparent power. Reactive power is the non-working power generated by the magnetic and inductive loads, to generate magnetic flux. The increase in reactive power increases the apparent power, so the power factor also decreases. Having low power factor, the industry needs more energy to meet its demand, so the efficiency decreases.
In this proposed system the time lag between the zero voltage pulse and zero current pulse duly generated by suitable operational amplifier circuits in comparator mode are fed to two interrupt pins of the microcontroller. It displays the time lag between the current and voltage on an LCD. The program takes over to actuate appropriate number of relays from its output to bring shunt capacitors into the load circuit to get the power factor till it reaches near unity. The microcontroller used in the project belongs to 8051 family. Further the project can be enhanced by using thyristor control switches instead of relay control to avoid contact pitting often encountered by switching of capacitors due to high in rush current.

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Acknowledgement i
Abstract ii
List of figures iv
List of tables vii
List of Abbreviation x
Table of content xi
Chaper-1 Introduction to Project
Chaper-2 Brief History of the work
Chaper-3 Literature Survey
Chaper-4 Working / Implementation of the Project work/ simulation
Chaper-5 Result Analysis
Chaper-6 Conclusion

Chaper-1 Introduction to Project

Our project proposes to minimize the energy consumption and thus reduce the power loss in industries and establishments by making use of a number of shunt capacitors. This substantially reduces the electricity bill in industries and establishments. The power factor is also known as the ratio of real power to apparent power. It is also represented as KW/KVA, in the equation KW stands for the active or real power whereas KCA stands for reactive + active or apparent power. The power generated by inductive as well as magnetic loads in order to create a magnetic flux is known as reactive power which is a non-working power. An increase in the reactive power increases the apparent power, thus decreasing the power factor. With low power factor there is an increase in the need of energy to meet industry demands, this decreases the efficiency. Our system works by feeding the time lag between zero voltage pulse and zero current pulse produced by suitable operation amplifier circuit working in comparator mode to 2 microcontroller pins. The time lag between voltage and current is displayed on a LCD screen. The project program controls the working and actuates required number of relays from the output that will get shunt capacitors into load circuit in order to get power factor until it reaches unity. An 8051 microcontroller fulfils this process.


The literature survey for this purpose was done with the intention to get the theoretical and statistical data about the project and to plan the execution of the project with success. Technical paper and research material were read and the relevant data and the concept were used in our project. The important research was listed below:

1. Power factor improvement of induction motor using capacitor bank
2. Automatic power factor correction using capacitive bank
3. Design & implementation microcontroller based controlling of PF.
4. Power factor correction using PIC microcontroller
5. Microcontroller based automatic power factor correction


An electrical loads operates on alternate current that requires an apparent power which consists of real power and reactive power. There is an immense power loss due to the presence of reactive power on the load. It is minimized by using the capacitor bank in parallel with the load which in turns provides the better power usage. Reactive power is the non-working power generated by the magnetic and inductive loads, to generate magnetic flux. The increase in reactive power increases the apparent power, so the power factor is also decreases, having low power factor, the industry needs more energy to meet its demand due to the large current and voltage requires to drive the circuitry, so the efficiency decreases.



Alternating current circuits Unlike Director Current Circuits, where only resistance restricts the current flow, in Alternating Current Circuits, there are other circuits aspects which determines the current flow; though these are akin to resistance, they do not consume power, but loads the system with reactive currents; like D.C. circuits where the current multiplied by voltage gives watts, here the same gives only VA.Like resistance, these are called ‘Reactance’. Reactance is caused by either inductance or by capacitance. The current drawn by inductance lags the voltage while the one by capacitance leads the voltage. Almost all industrial loads are inductive in nature and hence draw lagging wattles current, which unnecessarily load the system, performing no work. Since the capacitive currents is leading in nature, loading the system with capacitors wipes out it.

Capacitors for power-factor improvement

Whatever the power factor is, however, the generating authority must install machines capable of delivering a particular voltage and current even though, in a particular case, not all the voltage and current products is being put to good use. The generators must be able to withstand the rated voltage and current regardless of the power delivered. For example, if an alternator is rated to deliver 1000A at 11000 volts, the machine coils must be capable of carrying rated current. The apparent power of such a machine is 11 M V A and if the load power factor is unit this 11 MVA will be delivered and used as 11 MW of active power i.e. the, alternator is being used to the best of its ability. If, however, the load power factor is say, 0.8 lagging, then only 8.8 MW are taken and provide revenue, even though the generator still has to be rated at 1000A at 11 kV. The lower the power factor, the worse the situation becomes from the supply authorities viewpoint. Accordingly, consumers are encouraged to improve their load power factor and in many cases are penalized if they do not. Improving the power factor means reducing the angle of lag between supply voltage and supply current.

Location of power-factor improvement capacitor banks

Any installation including the following types of machinery or equipment is, likely to have low power factor which can be corrected, with a consequent saving in charges, by way of reduced demand charges, lesser low power factor penalties:

1. Induction motors of all types (which from by far the greatest industrial load on a. c. mains).
2. Power thyristor installation (for D.C. motor control and electro-chemical Processes).
3. Power transformers and voltage regulators.
4. Welding machines
5. Electric-arc and induction furnaces.
6. Choke coils and magnetic system.
7. Neon signs and fluorescent lighting.

Apart from penalties like maximum demand charges, penalty for low power Factor, the factory cabling and supply equipment can be relieved of a considerable wattles or reactive load, which will enable additional machinery to be connected to the supply without enlarging these services. Additionally, the voltage drop in the system is reduced.

The method employed to achieve the improvements outlined involves Introducing reactive kVA (kvar) into the system in phase opposition to the wattles or reactive current mentioned above the effectively cancels its effect in the system. This is achieved either with rotary machines (synchronous condensers)

1. TRANSFORMER (230 volt to 12 volt AC)
8. LCD
9. LM339
13. LED
14. 1N4007
Transformers convert AC electricity from one voltage to another with a little
Loss of power. Step-up transformers increase voltage, step-down transformers
Reduce voltage. Most power supplies use a step-down transformer to reduce the
Dangerously high voltage to a safer low voltage.

The LM78XX/LM78XXA series of three-terminal positive regulators are
Package and with several fixed output voltages,
Making them useful in a Wide range of applications.

A rectifier is an electrical device that converts alternating current (AC),
Which periodically reverses direction, to direct current (DC), current that flows in
Only one direction, a process known as rectification. Rectifiers have many uses
Including as components of power supplies and as detectors of radio signals.
Rectifiers may be made of solid state diodes, vacuum tube diodes, mercury arc
Valves, and other components. The output from the transformer is fed to the
Rectifier. It converts A.C. into pulsating D.C. The rectifier may be a half wave or a
Full wave rectifier.

Capacitive filter is used in this project. It removes the ripples from the
Output of rectifier and smoothens the D.C. Output.


TheAT89S52is a low-power high-performance CMOS 8-bit microcontroller with 8K bytes of in-system programmable Flash memory. The device is manufactured using Atmegs high-density non-volatile memory technology and is compatible with the industry standard 80C51 instruction set and pin out. The on-chip Flash allows the program memory to be reprogrammed in system or by a conventional non-volatile memory programmer. By combining a versatile 8-bit CPU with in-system programmable Flash on a monolithic chip, the
Atmel AT89S52 is a powerful microcontroller which provides a highly-flexible and cost-effective solution to many embedded control applications. The AT89S52 provides the following standard features: 8K bytes of Flash, 256 bytes of RAM, 32 I/O lines, Watchdog timer, two data pointers, three 16-bit timer/counters, a six vector two-level interrupt architecture, a full duplex serial port, on-chip oscillator, and clock circuitry. In addition, the AT89S52 is designed with static logic for operation down to zero frequency and supports two software selectable power saving modes. The Idle Mode stops the CPU while allowing the RAM, timer/counters, serial port, and interrupt system to continue functioning. The Power-down mode saves the RAM contents but freezes the oscillator, disabling all other chip functions until the next interrupt or hardware reset.


Relays allow one circuit to switch a second circuit which can be completely separate from the first. For example a low voltage battery circuit can use a relay to switch a 230V AC mains circuit. There is no electrical connection inside the relay between the two circuits; the link is magnetic and mechanical. The coil of a relay passes a relatively large current, typically 30mA for a 12V relay, but it can be as much as 100mA for relays designed to operate from lower voltages. Most ICs (chips) cannot provide this current and a transistor is usually used to amplify the small IC current to the larger value required for the relay coil. The maximum output current for the popular 555 timer IC is 200mA so these devices can supply relay coils directly without amplification.

This is the first interfacing example for the Parallel Port. We will start with something simple. This example doesn’t use the Bi-directional feature found on newer ports, thus it should work with most, if not all Parallel Ports. It however doesn’t show the use of the Status Port as an input for a 16 Character x 2 Line LCD Module to the Parallel Port. These LCD Modules are very common these days, and are quite simple to work with, as all the logic required running them is on board.


A load that is predominantly inductive, so that the alternating load current lags behind the alternating voltage of the load. Also known as lagging load. Any devices that have coils of wire in there manufacture can be classed as inductive loads. E.g. motors, solenoids and contactor coils are a few. Example of resistive loads can be baseboard heaters, filament light bulbs, toasters and stove top elements.


Shunt capacitor banks are used to improve the quality of the electrical Supply and the efficient operation of the power system. Studies show that a flat Voltage profile on the system can significantly reduce line losses. Shunt capacitor Banks are relatively inexpensive and can be easily installed anywhere on the Network.


It can be concluded that power factor correction techniques can be applied to the Industries, power systems and also households to make them stable and due to that the system becomes stable and efficiency of the system as well as the apparatus increases.
The use of microcontroller reduces the costs. Due to use of microcontroller multiple parameters can be controlled and the use of extra hardware such as timer, RAM, ROM and input output ports reduces. Care should be taken for overcorrection otherwise the voltage and current becomes more due to which the power system or machine becomes unstable and the life of capacitor banks reduces.
This project work is carried out to design & implement the automatic power factor
Controlling system using Microcontroller (AT89C52). Microcontroller senses the
PF by continuously monitoring the response from the ZCD.