Everything You Wanted To Know About Your Home Inverter

[By Electronics Infoline In-House Editorial Team]

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What is an Inverter?

An electronic device that can convert Direct Current (DC) into Alternating Current (AC) is named as Inverter. It is also known as ‘Power Adapter’. The inverter performs exactly opposite to a rectifier. It permits battery-based systems to run conventional house electrical devices like television, fan or computer, etc. using traditional home wiring [1].

The method of inverting low voltage DC power is basically completed in two steps. In the first step, the low voltage DC power is converted into high voltage DC power and in second step this high voltage DC source is converted into an AC waveform using PWM (Pulse Width Modulation). There is also another method to achieve this conversion i.e. firstly converting low voltage DC power to AC and then secondly boost the voltage to 120V by using transformer [2].

The technology related to inverter has made progress significantly. In addition to the conversion from AC to DC, many other services are provided by inverters to guarantee that it can work at optimal performance condition i.e. complex utility controls, system design engineering and in data monitoring. Post-installation services are also offered by manufacturers of inverters that are very essential to maintain energy fabrication and good level of performance i.e. O&M (Operation & Maintenance) services, quick Mean Time To Repair (MTTR) and preventative maintenance [3].

 

Types of Inverter

There are two types of inverter are available in the market i.e. modified sine wave and pure sine wave inverters. These inverters generate different outputs hence providing different efficiency levels.

• Modified Sine-wave Inverters

It is same as square wave inverter but has “stepping” appearance which relates its shape to a sine wave.  This is shown in Figure 1 in which the modified sine wave has imitated itself. This waveform is attained by the product of switching between the values at a fixed frequency.

The modified sine wave inverter supplies a cost-effective and simple solution for powering AC devices. All the devices do not operate accurately on the modified sine wave, for example, computers or medical equipment; these do not work properly with of distorted signals.

 

 

• Pure Sine-wave Inverters

These types of inverter are capable of simulating the AC power accurately generated from the grid. Mostly these inverters are costly than modified sine wave inverters because of their complex circuitry. However, this inverter is able to run all the electronic devices and also permitting inductive loads to operate faster. It also reduces the audio and electric noises from electronic equipment i.e. TV and fluorescent lights [4].

 

Home-based Inverters

Home-based inverter can be used easily by just connecting it to the battery and then plugging all the desired AC appliances into inverter. These are best used in times of load shedding i.e. no disconnection of power in case of load shedding. A rechargeable battery provides the required power to the inverter. This can be charged directly by any AC outlet. A domestic inverter has an in-built charger that facilitates this charging when AC mains power supply is available.

The battery can also be charged by solar panels. (See our article on An Overview of Home Solar Power Systems)

The power from the inverter is used in commercial and industrial areas where the supply of electricity is intermittent. These type of inverter are very useful in offices and homes [5].

 

Working of a Home-based Inverter

Sine wave pure inverters work as home-based inverters. This inverter is used to attain alternating sinusoidal current at the output of the transformer by giving sinusoidal current at the input. Figure 2 describes the working of an inverter. The oscillator provides the required sinusoidal current at the input. A widely used oscillator is Wien Bridge Oscillator made with Field Effect Transistor (FET).  In most of the cases of oscillating circuits, the output current is not enough to drive the coil. Output current needs to be amplified by an amplifier to generate a more powerful current to drive the primary coil winding of the transformer. If transformer losses are ignored then if the voltage increases current decreases but power remains the same. This means for the 1KW AC current at the output, 1KW DC current need to be applied on the input [6].

 

 

 

Figure 3 shows the block diagram of the generalized working of a home-based inverter. The design of an inverter is very simple. It comprises of DC voltage source, pulse generator, MOSFET, AC source and transformer.

 

 

The circuitry of an Inverter

Figure 4 shows the circuit diagram of sine wave inverter. The input of the circuit is a DC source which acts as a battery (Lead-acid rechargeable battery). IC 4047 is used to generate a continuous pulse. After receiving pulse wave from the oscillator, this pulse is given to the MOSFETs IRFZ44N through resistors. The output of the MOSFET is obtained from the drain. Two pairs of MOSFET are used in this circuit. MOSFETs are used for switching purposes in an inverter. From the MOSFETs, we get 12VAC sine wave output. Then a Center Taped Transformer is used to step up this signal to 220VAC. Now the obtained output is used as a load. MOSFETs’ pair acts as two kinds of Mode i.e. 1. Inverting Mode  2. Non-inverting mode. The output gained from these modes has a phase difference of 180 degrees [7]. Figure 5 shows the circuit which can convert 12VDC to 220VAC, 50 Hz sinusoidal waveform.

 

 

 

Inverter Installation Procedure

 

In order to install inverter at home, several things need to be kept in mind. A detailed procedure of installing an inverter is discussed below

• Firstly calculate the total power usage (Watt) of the house. This is done by adding wattage (power ratings) of the appliances which are needed to be powered by the inverter. For example Table 1 shows the names of appliances their power wattages and the total power consumed by them.

Table 1

Appliances	Power Rating	Total number	Total Power
Fans	60 W	3	180 Watt
Lights	40 W	3	120 Watt
Television	60 W	1	60 Watt
Total Watts			360 Watt

 

• Secondly, evaluate the inverter capacity. On point should be kept in mind that inverter VA rating should not be equal to the total power of load because if it is so then the inverter will not be able to drive the load due to power factor. Power factor varies from 0.6 to 0.8. VA rating of the inverter can be calculated by

Considering the above-mentioned values in table 1

[8]

• The third most important thing is to evaluate the battery capacity. Battery capacity decides the number of backup hours. An inverter is totally dependent on battery for its power requirement in order to run the appliances. The inverter life and performance highly depends upon the quality of the battery. Battery capacity is measured in Ampere hour (Ah). In general, 12V battery with 150Ah to 200Ah is used in homes. Battery capacity can be calculated as follows:

 

In general, you will need around an 800VA to 1100VA Inverter with a single 150Ah to 200Ah Lead-Acid Battery for normal home use. Or if your home has a little larger need, you can go with a 1200VA to 1500VA inverter model with two 12-Volts, 150Ah or 200Ah Batteries connected in Series, thus making the whole battery-bank a 24V one. In this case, always use an identical battery for both of them for best results.

You can purchase a full inverter system of your choice (among many models displayed) from Amazon India by clicking here.

Or if you are reading this article from the United States, Click Here to chose and buy one.

 

Batteries with a capacity of 100 Ah, 150 Ah, 180 Ah and 200Ah etc. are easily available in the market [9] [10].

India Link for Battery

USA Link for Battery

Safety Measures for Operating Home-based Inverter

There are some safety measures that need to keep in mind while operating inverters. Some are as follows

1. Your inverter should always be placed horizontally on a flat surface.
2. The apparatus should always be positioned in a dry and cool location.
3. Apparatus should not be operated with wet hands because water is the conductor of electricity and can cause electric shocks.
4. The machine should not be located near any heating vents. Also, direct sunlight exposure is not good for inverters.
5. The ideal temperature for inverters is between 20 and 40 degree Celsius.
6. Inverters should be kept clean and well ventilated for better working.
7. Home should have proper earthing to evade accidental electrocution [11].

 

Benefits of Home Inverters over Power Generators

Inverters have become a must-have in every house and office. Before inverters, power generators were used that were very big in size. Inverters are more or less the same as generators but technology has made it modern.  There are many benefits of using inverters over power generators. Some are mentioned below:

1. Fuel Efficiency– Home inverter uses batteries to store energy and in absence of electricity this stored energy can be used as a backup. Whereas power generators operate at a constant speed of 3600 rpm which need plenty of diesel or petrol. As the home inverter does not need any fuel to run at high speed, it just needs an AC outlet to charge the batteries.
2. High-Quality Electrical Output And Parallel Capability– Inverter is capable to generate power same as the power used in homes. An inverter can be paired with another identical unit in order to double the power. The feature of parallel capability in inverters permits the usage of two small and lightweight inverters for running any type of applications at home. This feature is not available in generators.
3. Maintenance– The conventional generator requires regular maintenance for generating required electrical output. A generator should be used on regular basis otherwise if it remains unused for 30 days or more then the oil will drain and carburetor will be dried. Unlike generators, the inverters do not need any special care for maintenance as only their batteries need an inspection check once a year [12].
4. Noise –Inverters produce far less noise than conventional generators. Generators are loud because of their requirement of running at a constant speed of 3600 rpm to fabricate energy. On the other hand, inverters’ speed can be regulated according to the power that is needed to generate due to the presence of microprocessors.
5. Portable – Inverters are not as huge as old fashioned generators. Inverters are smaller in size and easier to handle and store. Due to their compact volume, it is easier to carry them anywhere like for camping or hiking [13].

 

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References

1. Windy Dankoff, “How to Choose an Inverter for an Independent Energy System”, Home Power #82, April-May 2001, PP 74-78.
2. Jim Doucet, Dan Eggleston, Jeremy Shaw, “DC/AC Pure Sine Wave Inverter”, WPI, 2006-2007.
3. com/2013/04/how-do-solar-inverters-work/
4. com (2005). Frequently Asked Inverter Questions. Retrieved November 12, 2006, from http://www.donrowe.com/inverters/inverter_faq.html#modified.
5. http://www.electronicshub.org/inverter-for-home/
6. com/en/how-does-an-inverter-work.html
7. ALLDATASHEET.COM/IRFZ44N.pdf Accessed: 25 November, 2010
8. https://www.elprocus.com/how-to-select-the-best-inverter-for-home/
9. http://www.zelect.in/inverter/inverter-buying-guide
10. https://www.mrright.in/ideas/appliances/inverter/how-to-choose-the-right-inverter-battery-for-your-home/
11. http://www.idc-online.com/technical_references/pdfs/electronic_engineering/Working%20and%20Benefits%20of%20Inverter%20for%20Home.pdf
12. http://www.3benefitsof.com/3-benefits-of-inverter-generator/
13. http://www.educationextra.org.uk/2017/10/19/choose-inverters-standard-ones-home/
14. Raman Waghaye, Chakradhar Ambagade, Prajakta Sarve, Snehal Chopkar, Reena Girhepunje, Vinod Buddhe, “Design and Verification of Pure Sine Inverter”, IJRESAT, March 2017.
15. https://www.nantech.in/tips-to-choose-the-best-inverter-and-battery-for-home/
16. https://www.semprius.com/pure-sine-wave-inverters-how-do-they-work/