Inverter: Types and Applications

Inverter Types and Applications

An inverter is a device used to convert DC power into AC power. The inverter is not a power generator, because it not produces electrical energy. The inverters converts one form of electrical energy into another form of electrical energy. Therefore, it is a power converter, not a power generator.

The device that has the opposite function of inverter that is the Rectifier. The rectifier used to convert the AC power into DC power.

The input of the inverter is a stable DC power source like a battery. The input voltage depends on the design and the applications.

  • For smaller consumer and commercial inverters, which works on the rechargeable lead-acid battery, it works on 12V DC.
  • For the home energy system, common voltages are 24V, 36V, or 48V.
  • For solar PV panels, the input voltage is between 200V to 400V.
  • For an electrical vehicle, the input voltage is between 300V to 450V.
  • For the HVDC transmission line, the input voltage is hundreds of thousands of volts.

Types of Inverter

The inverters are classified according to the output waveform, according to the source of supply, and according to type of source.

According to Output Waveform

According to the output waveform, the inverters classified into three types;

  • Square Wave Inverters
  • Pure Sine Wave Inverters
  • Modified Sine Wave Inverters (quasi-sine wave inverters)

Square Wave Inverter

This is a simple type of inverter. The output waveform of this type of inverter is a square wave. Generally, for practical use, this type of inverter not used. Because the square wave is not a suitable waveform for the regular household, commercial, or industrial appliances.

The construction and design of the square wave inverters are simple and the cost is very cheap. If this type of inverter is connected to the audio equipment, it will produce a humming sound. And it is unsuitable for sensitive electronics.

Sine Wave Inverter

The sine wave inverter is best in performance and efficiency. But, the cost of this inverter is very high. The shape of the waveform of the power of utility is a sine wave. And the waveform of this type is exactly matched with the waveform of the utility power.

This type of inverter is suitable for all types of load.

The construction and design of this inverters are very complex. The waveforms are smooth and distortion is very less.

Modified Sine Wave Inverter

In a modified sine wave inverters, the output waveform is not a pure sine wave. The shape of this waveform is similar to the staircase.

The modified sine wave inverter is a sum of two square wave inverters one of which shifted by 90 degrees.

The output waveform is very similar to the sine wave. Many types of equipment work properly and operate quite well on a modified sine wave inverters. When the load is resistive in nature, the modified sine wave inverters works very well.

But, the efficiency of this inverter is slightly less than the efficiency of the pure sine wave inverters and it produces humming sound in such applications. The cost of this inverter very less compared to the pure sine wave inverters.

Therefore, when the cost considered the modified sine wave inverter a better choice among all other types of inverters.

According to Source of Input

According to a source of input; The inverters classified in two types;

  • Current Source Inverter (CSI)
  • Voltage Source Inverter (VSI)

In CSI, the input is a current source. This type of inverters widely used in the medium voltage industrial application, where the high-quality current waveform is compulsory. But CSI are not popular.

In VSI, the input is a voltage source. This type of inverters is widely used in all applications because it is more efficient and has higher reliability and faster dynamic response. VSI is capable of running motors without de-rating.

According to Type of Supply

The output of the inverter is AC power and there are two types of AC power; single-phase and three-phase. According to output power inverters can classify into two types;

  • Single-phase Inverters
  • Three-phase Inverters

This is depending on the utility connection. For a small load, a single-phase connection provided and for a large load, the three-phase connection provided. Generally, for domestic load single phase connection used and for industrial load, a three-phase connection used.

Applications

  1. An uninterrupted power supply (UPS) supplies AC power with the help of an inverters and battery combination.
  2. Speed Control of Electric Motor: An inverter is designed to produce a variable output voltage and by controlling the output voltage of the inverters, we can control the speed of an electric motor.
  3. In the compressor of refrigerator and air-conditioner: In the simple inverters, the single-speed compressor switches on and off periodically. But in inverters compressor, VFD (variable frequency drive) used to control the speed of compressor motor and according to this control of cooling is done.
  4. Solar: Output of solar PV panels is DC. So, we have to convert it to AC for that inverters are used.
  5. HVDC transmission line: For bulk power transmission, the HVDC transmission line has more advantages than the HVAC transmission line. In this transmission network, power generated in AC and convert in DC with the help of a rectifier and transmit this DC power for long-distance. The inverters used to convert the power into AC at the receiving end of the transmission line.

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