[By Electronics Infoline In-House Editorial Team]
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 .
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 .
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 .
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.
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.
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 .
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 .
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 .
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.
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 . Figure 5 shows the circuit which can convert 12VDC to 220VAC, 50 Hz sinusoidal waveform.
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
Considering the above-mentioned values in table 1
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.
Batteries with a capacity of 100 Ah, 150 Ah, 180 Ah and 200Ah etc. are easily available in the market  .
There are some safety measures that need to keep in mind while operating inverters. Some are as follows
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: