The Engineering Projects

Introduction to Inverters

Hello friends, I hope you all are well and doing great in your lives. In today's tutorial, I am going to share the Introduction to Inverters. An inverter converts DC voltage or current to AC voltage or current. You can also say that it transfers or converts power from a DC source to an AC load. The aim of this circuit is to supply AC power similar to the one that we receive at homes.

Firstly, I am going to share some basic information related to inverters. In the second section, I will give you the basic configuration or parts of it and in the last section, I will tell you the types and applications. Let's now get started with the Introduction to Inverters:

Introduction to Inverters

• An inverter is connected to a DC source and it converts it into AC power in its circuit.

The details on input and output are as under.

• The input is DC power. The value of input voltage depends upon the application. Some applications require 12 V while some may require very high voltages of thousands volts.
• The ideal output of an inverter is a sinusoidal waveform. Such a wave gives continuous flow of power. But the output from the circuit is generally not ideal. It gives output in the form of square wave, quasi-square wave or PWM.
• The conversion of DC power to AC power can be done using two approaches. Both do conversion in two steps.
  • In the first approach, a low voltage DC power is converted into high voltage DC power and then in the second step this high voltage DC power is converted to AC power.
  • In the second approach, a low voltage DC power is converted to low voltage AC power and then this output is stepped up to high voltage AC power.
• They are available in different types in market. They exist in different shapes and sizes. They vary from low power to high power functions.

Let’s move towards the second section in which I am going to tell you all about the main parts of an inverter’s circuit.

Parts of an Inverter

In this section of my article, I am going to tell you about the configuration and constituents of the circuit. The generally used ones may consist of these four parts:

1. Converter

This is the circuitry to convert commercial power to required DC power.

2. Smoothing Circuit

This circuit smooths the pulses in DC power.

3. Inverter

This is the most important part whose purpose is to convert DC to AC power.

4. Control Circuit

This part controls the entire inverter operation.

In the next section, I am sharing some knowledge on the classification of inverters.

Classification

Inverters can be classified according to a number of different factors.

Output Waveform

First classification is based on the nature of output waveform for example, sine, square, quasi-square or PWM. Inverters can produce a pure sine wave or a modified sine wave. A modified sine wave is the one which is more close to a square wave.

Power Device

Second classification is based on the type of power or switching device used. This power device may be one from transistor, thyristor or MOSFET etc.

Configuration

On the basis of configuration, it can be classified into three types which are given below.

Single Phase Half Bridge

• This type of inverters is used in low power applications and also known as inverter leg.
• The circuit of single phase half bridge inverter consists of 2 choppers and a DC source with 3 wires.

Single Phase Full Bridge

• Full bridge inverters are also used for applications which require low power.
• The circuit consists of 4 choppers and a DC source with 3 wires.

Three Phase Inverters

• Three phase inverters are used in medium to high power applications.
• They provide a three phase voltage source.
• It is used where frequency, amplitude and phase of the voltage should be controllable.

Now I am moving towards the last section of this article where I will be sharing some applications of this device.

Applications

Inverters got a variety of applications. I am going to mention some of those.

• They are used in AC motor drives with adjustable speed.
• They are used in UPS (Uninterruptable Power Supply) which is a very common application now a days.
• They are being used in portable devices.

   

• Inverters are used in controlling air flow. For example they are used in fans, blowers and drying machines.
• They are used in power generation systems.
• Inverters have helped in increasing efficiency of machines and decreasing their sizes. To change speed and other conditions is now easier than before. They are used in driving machine tools, tables, etc.
• They also find application in conveyor belts as they can be used for controlling speed.
• Inverters are used where there is a need to run AC devices from batteries.
• They are used in industries in packaging machines, weighing machines and carts.
• They are also used in hybrid and electric cars.
• They also find applications in motor speed controllers.
• This device is used in voltage compensators.

So, that's all about the Introduction to Inverters. I hope you will get some knowledge from this Introduction to Inverters. Let us know about your questions in the comment section.

Major Components of Inverters

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1.	Basics of Inverters With Topology
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Hello guys, in the last post I have explained the basics of inverters along with its types and also the inverters topology in other words working of inverters. Now in this post I am gonna explain the major components required for making an inverter. This post is not giving you any technical knowledge about inverter but to workout with inverters its necessary to go through its basic components.

I have divided this tutorial into four parts which are shown below. This is a step by step guide to design and build an inverter and I hope at the end of this tutorial you guys will be able to design your own inverter. I tried my best to keep it simple but still if you guys got stuck at any point ask in comments and I will remove your query.

Major components of an inverter

• An inverter design and components vary with requirements but following components are most commonly used in designing an inverter.

Microcontroller

• Microcontroller is the main and integral part of an inverter. The main working of microcontroller is to control the switching of signals according to the requirements.
• A single microcontroller can perform multiple functions (e.g.) generating PWM for switching, controlling the protection systems etc.
• There are various types and families of microcontrollers available in the market, for example :
  • PIC Microcontrollers.
  • AVRs (ATMEGA series).
  • Atmel.
  • Arduino.
  • FPga (etc).
  • 8051 Microcontrollers Projects.

•   Depending on the design specifications, any microcontroller can be used.

Bipolar junction transistors (BJTs)

• BJT or a bipolar junction transistor is a three layered device which is capable of controlling the current flow.
• In a BJT, a small current at the input of the device can control larger currents at the output. Thus, BJTs can amplify currents.
• They can be used as a relay driver, as a switch, as a constant current source, as an amplifier (etc.).
• Circuit symbol of a BJT is given in figure below :

FIGURE 1 : BJT symbols

Types of BJTs

• There are two types of transistors, NPN and PNP transistors

1. NPN Transistor :

• NPN is one of the two types of bipolar transistors, in which the letters "N" and "P" refer to the majority charge carriers inside the different regions of the transistor.
• In other terms, an NPN transistor is "on" when its base is pulled high relative to the emitter.
• The arrow in the NPN transistor symbol is on the emitter leg and points in the direction of the conventional current flow when the device is in forward active mode.

FIGURE 2 : PNP Transistors 2. PNP transistor

• PNP transistors have two layers of P-doped material and in between these two layers, there's a small layer of N-doped material.
• A small current leaving the base in common-emitter mode is amplified in the collector output. In other terms, a PNP transistor is "on" when its base is pulled low relative to the emitter.
• The arrow in the PNP transistor symbol is on the emitter leg and points in the direction of the conventional current flow when the device is in forward active mode.
• Below figure shows both NPN and PNP transistors.

FIGURE 3 : PNP Transistors

H-Bridge

• H –bridge is a topology in which four switching devices BJTs, MOSFETs or IGBTs are integrated together in a single circuit.
• The name H-Bridge is given to it because of the typical arrangement of this circuit.
• Mainly used switching devices in the H-bridge circuits are BJTs, MOSFETs or IGBTs.

Working

• In an H-bridge, corresponding to the figure below when the switches S1 and S4 are closed, the switches S2 and S3 are open.
• Thus a positive voltage issupplied across the motor or any other load attached to it instead of motor (e-g) transformer.
• When S1 and S4 switches are opened, and S2 and S3 switches are closed, the voltage is reversed, supplying negative voltages to the load.
• A problem with this is that the switches S1 and S2 should never be closed at the same time, as this causes a short circuit on the input voltage source.
• The same thing applies on the switches S3 and S4. This condition is generally known as the shoot-through condition.
• Following figure describes the above phenomena.

  FIGURE 4 : H-Bridge Working

MOSFETs

• The Metal-Oxide-Semiconductor-Field-Effect-Transistor (MOSFET) is a voltage controlled device and requires a very small input current.
• It is mainly used for switching of electronic signals as its switching speed is very high.
• It is the most commonly used FET in low-power high-frequency circuits.
• The MOSFET is composed of a channel of n-type or p-type semiconductor material, and is accordingly called an N-MOSFET or a P-MOSFET.
• Circuit symbols of MOSFET are shown in the figure below :

FIGURE 5 : MOSFET Types and symbols

Types of MOSFETs

There are two main types of MOSFETs.

• The Depletion-type MOSFET (DMOSFET)
• Enhancement-type MOSFET (E-MOSFET)

Filters

• At times it is desirable to have circuits capable of selectively filtering one frequency or range of frequencies out of a mix of different frequencies in a circuit.
• A circuit designed to perform this frequency selection is called a filter circuit.

Low-Pass Filters

 

• A low-pass filter is a circuit offering easy passage to low-frequency signals and difficult passage to high-frequency signals.
• There are two basic kinds of circuits capable of accomplishing this objective, and many variations of each one.

LC Filters

• An LC filter is a low-pass filter which consists of an inductor attached in parallel with the capacitor and the load.L and C connected together act asan electrical resonator.

LC Filter over RC Filter

• RC filters have R thus they dissipate power. They have attenuation even in the pass band.
• To achieve a narrow transition band, RC circuits have to be of higher orders.
• Only certain types of filters can be implemented by an RC filter.
• Whereas, LC filter does not dissipate power.
• Better characteristics can be achieved by the LC filter than RC with a lower order.
• Thus it is desirable to choose an LC over an RC in the case of an inverter.

Transformer

• A transformer is used to step up or step down the electrical voltages.

FIGURE 6 : Ideal Transformer

Working of Transformer

• A changing electric flux in the primary of the transformer creates a changing magnetic field which induces a changing voltage in the secondary.
• By adding load, one can transfer energy from one part to another.
• The secondary voltage Vs of an ideal transformer is scaled from the primary voltage Vpby a factor equal to the ratio of the number of turns of wire in their respective windings.
• By appropriate selection of the numbers of turns, a transformer thus allows an alternating voltage to be stepped up by making Ns more than Np or stepped down,by making it less.
• If the secondary coil is attached to a load that allows current to flow, electrical power is transmitted from the primary circuit to the secondary circuit.
• Ideally,
  • Pin = Pout
  • IpVp= IsVs
• Where:
  • Pin = Input Power.
  • Pout = Output Power.
  • Ip = Primary Current.
  • Vp = Primary Voltage.
  • Is = Primary Current.
  • Ip = Primary Voltage

Basics of Inverters With Topology

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Give Your Suggestions !!!
1.	Basics of Inverter With Topology
2.	Major Components of Inverters
3.	Pure Sine Wave Inverter Design With Code
4.	Modified Sine Wave Design With Code

Hello friends, hope you all are fine and enjoying good health. I have recently posted a project of my friend named as Design & Development of Hybrid Renewable Energy System, which is a pure electrical project.After that project, I thought of sharing some common electrical modules.

So first of all, I am gonna explain all about inverters. I have divided this tutorial into four parts which are shown in the table. This is a step by step guide to design and build an inverter and I hope at the end of this tutorial you guys will be able to design your own inverter. I tried my best to keep it simple but still if you guys got stuck at any point ask in comments and I will solve your query.

What is an Inverter

• An Inverter is an important electrical instrument used to convert DC voltage into AC voltage, its quite easy to explain what is an inverter but its too way difficult to design an inverter.
• In projects, mostly inverter is used to convert the 12V DC voltage into 220V AC voltage, obviously first it is converted to 12V AC and then stepped up to 220 volts (mainly) for the consumers.

Types of Inverters

There are various types of an inverters such as :

• Pure Sine-wave inverters.
• Modified sine wave inverters.
• Square wave inverters.
• Multi-level inverters.
• Resonant inverters (etc.).

The main three of which are discussed below in detail.

Modified sine-wave inverters

• The output of a modified square wave, quasi square, or modified sine wave inverter is similar to a square wave output except that the output goes to zero volts for a time before switching positive or negative.
• It is quite simple to design and is compatible with almost every electrical equipment except for sensitive or specialized equipment,e.g. laser printers, audio equipments etc.
• Most AC motors can run on this power source but with reduction in efficiency of approximately 20%.

Sine-wave inverters

• A pure sine wave inverter is the best form of inverter as it produces perfect sine wave and the energy dissipation in it is minimal.
• Pure sine wave inverter is compatible with all electrical devices.
• Its designing is complicated as compared to all other inverters.

Square wave inverters

• The square wave output has a high harmonic content, not suitable for certain AC loads such as motors or transformers.
• Square wave units were the pioneers of inverter development.

Inverter topologies.

• There are many different power circuit topologies and control strategies used in inverter designs.
• Different design topologies address various issues that may be more or less important depending on the way that the inverter is intended to be used.

First Method

• Inverters normally use H-bridge configuration.
• However, the voltage level at which, the H-bridge is operated can be varied.
• The normal inverters convert the DC into AC at 12 Volts.
• After this inversion, this 12Volt AC is stepped up into 220 Volts AC by the means of a transformer.
• The advantage of such an approach is that the bridge construction is easy, as it is not exposed to high voltages.
• The disadvantages accompanying such an approach are :
  • The transformer steps up the harmonic content.
  • The size and weight of the transformer increases considerably, as the capacity of inverter is increased.

Second Method

• To overcome such problems, we can use a topology of converting DC into AC at the output voltage of the inverter.
• At first, boosting the battery voltages by the means of a DC-DC converter and then giving these voltages toa specially designed Hbridge.
• This arrangement can overcome the previously mentioned disadvantages.
• The main disadvantage of such an approach is that the bridge circuit becomes too complex.

So, that was the basics of Inverters, you should also have a look at Introduction to Multilevel Inverters. If you have any problem then as in comments.