Best power inverter for home appliances

by Orson Z. Overseas Trade Manager

Best power inverter for home is to provide uninterrupted power to run household electric devices. These power inverter for home are available in different voltage and load capacities. In the basic design of the home inverter a DC (battery) source is connected to a transformer through the center tap of the primary winding.

The alternation of DC in the primary winding of the transformer produces alternating current (AC) in the secondary circuit. This will be 230 /110 Volt AC and can operate all the electric devices.

Efficiency of the Power Inverter for Home

The quality of the output wave form (230 volt AC) from the inverter determines its efficiency. The quality of the inverter output wave form is expressed using Fourier analysis data to calculate the ‘Total Harmonic Distortion’ (THD). THD is the square root of the sum of the squares of the harmonic voltage divided by the fundamental voltage.

THD = √ V2 2 + V3 2 + V4 2…………. Vn 2 / V1

Types of inverter

The type of power inverter you should choose depends on the type of power output you require.

Pure sine wave power inverter for home

Alternating current has continuously varying voltage, which swings from positive to negative. This has an advantage in power transmission over long distance. Power from the Grid is carefully regulated to get a pure sine wave. Also the sine wave radiate the least amount of radio power during long distance transmission. Its quality is excellent and almost all electrical and electronic appliances work well in sine wave inverter.

The sine wave is the AC waveform we get from the domestic lines and from the generator. The major advantage of sine wave inverter is that all of the house hold appliances are designed to operate in sine wave AC. The sine wave is a form of soft temporal rise voltage. And it lacks harmonic oscillations which can cause unwanted counter forces on engines, interference on radio equipments and surge current on condensers.

Modified sine wave inverter

Modified sine wave is designed to simulate a sine wave since the generation of sine wave. This waveform consists of positive voltage, dropping abruptly to zero for a short period. It is dropping again to a negative voltage. It then go back to zero again and returning to positive. This short pause at zero volts gives more power to 50 Hz fundamental frequency of AC than the simple square wave.

Inverters providing modified sine wave can adequately power most house hold appliances. It is more economical but may present certain problems with appliances like microwave ovens, laser printers, digital clocks and some music systems. 99% of appliances run happily in modified sine wave. Instruments using SCR (Silicon Controlled Rectifier) in the power supply section behave badly with modified sine wave. The SCR will consider the sharp corners of the sine wave as trashes and shut off the instrument. Many of the Laser printers behave like this and fail to work in inverters and UPS providing modified sine wave power. Most variable speed fans buzz when used in modified sine wave inverters.

As you can see from this example, though the modified and pure sine wave produce the same levels of output.

Square Wave Power Inverter

This is the simplest form of output wave available in the cheapest form of inverters. They can run simple appliances without problems. Square wave voltage can be easily generated using a simple oscillator. With the help of a transformer, the generated square wave voltage can be transformed into a value of 230 volt AC or higher.

Terms related to Inverter

Watt (W)

Watt is the measure for how much power a device uses. If a device uses 100 watts, it is simply the voltage times the ampere (rate of current).If the device takes 10 Amps at 12 Volt DC, it uses 120 watts power.

Watt Hour (WH)

A watt hour (or Kilo Watt hour – kWh) is simply how many watt times, how many hours the device is used. If the device uses 100 watts for 10 hours, it is 1000 watt hour or 1 kWh. The electricity tariff is based on kWh.

Ampere (A)

It is the measure of electrical current at the moment. Amps are important to determine the wire size for connecting the inverter to the battery. Low gauge wire will heat up and burn if heavy current flows through it from the battery.

Ampere Hour (Ah)

Amp-Hour usually abbreviated as Ah is the Amps x Time. Ah is the measure of battery capacity which determines the backup time of the inverter

Volt Ampere (VA)

It represents the maximum load capacity of the inverter. Commonly available inverters are 500 A, 1000 VA, 1500 VA etc.

Peak power and Typical or Average power

An inverter needs Peak or Surge power and Typical or Average (Usual) power. Peak power is the maximum power that an inverter can supply usually for short time. Some heavy current appliances like motor and refrigerator require a startup peak power than when running. Typical power is the power that the inverter gives on a steady basis. This is lower for the peak power. Typical power is useful in estimating the battery capacity.

Selecting the Best Power Inverter for Home

Before selecting the inverter, it important to calculate the total power consumption of the appliances that are going to be connected to the inverter.

It is important to note that the power consumption (Current drain) increases when the driving voltage decreases. When the input voltage drops in the domestic supply lines from 230 V AC to 200 VAC, electric devices will consume more current. For example a load rated 300 Watts (like Fridge) operating in 230 volts uses 1.4 Amps in one hour. The same load takes 1.5 Amps if the line voltage drops to 200 volt during peak hours (6pm- 9 pm). So it is advisable to switch off high current devices during peak hours. This conserves energy as well as reduces the electricity bill. If heavy loads are running in inverter, battery voltage diminishes from 13.5 volts to 12 volts with in a short time. This reduces the backup time.