DESIGN AND CONTRUCTION OF 1KVA INVERTER

BACKGROUND

Inverters are widely used in every aspect of life to provide electrical power for our daily activities.

Inverters are used in situation where low voltage DC sources such as batteries and solar panels must be converted to AC in other to power electrical appliances. One example of such situation would be converting a DC Voltage from a car battery to power a laptop, television, cell phones etc.

The method in which the low voltage DC power is converted to AC is known as inversion. In this circuit a 12volts dc battery is being used with some electronic components to convert the dc to ac, and a transformer is used to step up the voltage to 220volts ac.

I know some people have been surfing the net in other to get functional circuit diagrams but to no avail cause majority of the circuits on the net are half way worked, some do not even work. Not to worry you’re at the right place. At Eng Updates we avail to you functional circuits you could work on for personal studies, research, DIY projects, degree projects etc. Just try them and thank us latter.

CONSTRUCTION

Components needed

1.     Resistors

2.     Capacitors

3.     Diodes

4.     Inductor

5.     Transistors

6.     MOSFET

7.     SG3525IC

8.     NE555 timer

9.     Relays

        Circuit Diagram

    

Note: the value of all the components is on the diagram

            VR1 is used to set the output frequency of the inverter

             VR2 is used to set the output voltage

              VR3 is used to set the battery low voltage shutdown

The tools and instruments used include:

1. Lead and Soldering Iron

2. Lead sucker

3. Cutter

4. Razor blade

5. Plier

6. Digital Multimeter

7. Vero and bread board

DETERMINATION OF THE OSCILLATING FREQUENCY

By supplying a 12Volt DC to the IC SG 3525 PWM, the frequency of the oscillating signal was determined using a 10KΩ variable resistor connected in series with another 56KΩ resistor  and both connected in parallel with 0.22µF to form the RC time constant network.

Frequency, F = 1/1.1*Ct*Rf     where

Time Capacitor (C_T) = 0.22µF

Fixed Resistor (R_F) = 56KΩ

Variable Resistor (V_R) = 10KΩ

Time Resistor (R_T) =56KΩ+10KΩ = 66KΩ

Therefore,

F= 1/1.1*0.22¯6*66k

F= 62.6Hz

It should be noted that the potentiometer was varied till the frequency of the signal was 50Hz.

CALCULATION OF  TRANSFORMER PARAMETERS
The power Rating for the Inverter transformer (KVA) =1.0KA , E2=12V
Assuming the efficiency of transformer =85%
Then Input rating =output /Efficiency=1000VA/0.85=1176VA
Ip = PI / VP VP = 260V
Ip = 1176 / 260 = 4.5A
Ip = Po / Vs Vs = 12V
Ip = 1000 / 12 = 83.3A
For practical design of inverter transformer
Number of turns per volt for both primary and secondary winding is given by;
NT per V= 7/A
Where A is the area of transformer former in sq. inch
Former area A is 2.3inch by 1.5inch = 3.45sq.inch
NT per V= 7/3.45=2.03

NT per V= 2 (approximate value).
Primary Winding
Charger tapping winding turns
Np1= NT per V * E1=220V
Np1 = 2 * 220 = 440turns
Inverter (out) tapping winding turns
NS2= NT per V * E3=260V
NS2 = 2 * 260= 520turns
Difference of Inverting and Charging turns = 520 – 440 = 80turns.
For the primary windings, charging tapping is brought out after 440 turns and an addition 80 turns is
made for the inverter output tapping.
Secondary Winding
Secondary turns Ns= NT per V * E2 = 12V
Ns= 2 *12= 24turns. (Bifilar winding)

SWG Estimation
Standard Gauge Weight, SGW, can be estimated as follow;
Considering conduction current density J (with fixed value of 2.5A/mm2) and windings coil current.
For Ip =   4.5A, the corresponding gauge from tables is 24SWG and
For Is = 83.3A, the corresponding gauge from tables is 13SWG

complete 3.5kva inverter with the same diagram but little modification on the power mosfet and transformer

NOTE

The following maintenance practices and safety precautions are suggested to improve the life span of the system and prevent hazards to the users.

1. Dead batteries should not be used with the inverter

2. The battery terminals should not be removed too often. When it is removed, placement of correct polarity must be ensured.

3. The inverter must be kept in a moderate temperature environment.

4. The inverter should be shut down when not in use.

5. The inverter should always be partially loaded (not more than 75% of its maximum capacity).

6. The use of inductive loads like refrigerator, induction machines etc. on this inverter (1KVA) should be avoided, however inverters with much higher ratings can be used to power appliances with much power usage.

Please if this article helped you give us feedback by commenting below and you can also suggest areas of improvement.

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RESISTORS AND THERE COLOR CODING

 A resistor is a passive two terminal electronic component that is used to reduce the flow of current in a circuit.

All resistors have their power ratings, which is the maximum power a resistor can dissipate without damaging the resistor.

 Therefore a 1watt resistor with a resistance of 100ohms can pass a current of a current of 100miliAmpere whereas a resistor of 0.25watts of the same resistance could only pass a current of 50mA, if the current level where exceeded in either case for any length of time, will cause the resistor to overheat and burnout . There are different types of resistor which is shown below.

TYPES OF RESISTOR

        I.            FIXED RESISTORS : These are resistors with fixed value, which means that there value cannot be varied

Fixed Resistor Symbol

      II.            VARIABLE RESISTORS: These are resistors that has a variable point where you can change the resistance of the resistor from minimum to maximum. below shows resistor color code

Variable Resistor Symbol

RESISTOR COLOR CODING

Common resistors found in different electronic circuit are marked with different color in their body, this is done because of the small size of the resistors and their values are difficult to print on their body.

The first colour on the body of a resistor indicates its first digit as shown in the table above while the second colour indicates its second digit, the super script in the 3^rd band indicates the number zeros to be added to the first and second band in other to obtain the resistors value. The tolerance value shows the minimum and maximum range of value for any given resistor.

Finding a resistor value with its color code> example  A resistor with the following color code RED,RED,BROWN and SILVER will have the value 220 + or – 10percent which means the value of the resistor will fall between 220+22 and 220-22 that is within the range of 198ohms and 242ohms.

LETTER CODE OF A RESISTOR AND ITS MEANING

Letter code is used in some resistors to represent their value due to the body structure where color code cannot be printed on them, the table below shows a clear picture of resistor value representation.

 

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HOW TO INSTALL AN INVERTER WITH SOLAR PANEL

 Simple guide on how to install inverter system

An inverter is a power electronics device that converts direct current (DC) to alternating current (AC). The dc source can either  be a battery or directly from sun using photo-voltaic cell (solar panels).

List of items needed for installation

1.     An inverter system

2.     A solar panel and  charge controller

3.     batteries

4.     Connecting cables

5.     Cable locks

6.     Circuit breaker

7.     Lastly the load

STEP ONE 

To connect the panel to charge controller there are terminals mapped out for panel and battery,

Connect the positive and negative terminals of the charge controller to the panel positive and negative using 16mm industrial flex cable or higher size depending  on the rating of the panel and batteries to be charged. the picture below shows a 12/24volts 130watts  solar panel.

STEP TWO

This shows a 60amps charge controller to be connected with the battery and solar panel terminals indicated on the body.

STEP THREE

Connect the charge controller positive and negative terminal to the battery terminals and then connect the battery to the inverter  system making sure that the polarities are considered.

Warning:

Make sure that the battery positive terminal is connected to the inverter positive terminal  and the negative terminal  is connected to the inverter negative terminal. Ensure that the inverter is in OFF state before making any connection.

STEP FOUR

Connect the output of the inverter to the breaker >Reason: to prevent damage to the system when there is short circuit or overload.

Finally connect the output of the breaker to your load. checkout our previous post for connection diagram Inverter wiring diagram

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REGULATED D.C POWER SUPPLY

What is power a regulated d.c power supply?

A regulated dc power supply (also know a linear power supply), is an embedded circuit consisting of various component such as transformer, diode, capacitors, resistors and the voltage regulator which can be zener diode or LM70s IC.

Today almost every electronic device need a dc power supply for its smooth operation and the need to be operated within certain power supply range. This required dc voltage (which can be derived from a battery) or directly from AC mains through a regulator.

 The diagram below shows a 5volts regulated dc power supply.

List of components

1.     230v – 12volts 1A stepdown transformer

2.     1A bridge rectifier

3.     Polarized capacitor 470uf  50v

4.     Non-polarized capacitor 0.01uf

5.     Voltage regulator LM705

6.     Resistor 1k

7.     Led

Working principle

The heart of this regulated dc power supply is the LM705 as it determines the constant output voltage.

A 230v alternating current is input to the primary of the transformer and its being stepdown to 12v AC, the bridge rectifier converts the AC voltage to DC which passes through filtering capacitors C1 and C2 then the regulator regulates the dc voltage to 5volts constant output which is also filtered by capacitor C3. Led serve as an indicator and resistor 1k is used to limit the current entering into the led.

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