Inverters are basically used to convert Direct current into Alternating current.This can be achieved by using Thyristor such as SCR, TRIACetc.For single phase inverters, two thyristors (SCRs) are required similar to that of Diode rectifier.
Based on type of connections of semiconductor devices, inverters are classified as under
Single Phase Series Inverter:In a series inverter, the commutating elements L and C are connected in series with the load resistance R. The load resistance R can also be in parallel with C.The value of L and C are such that those form an underdamped circuit.
Single Phase Parallel Inverter:During the working of this inverter, capacitor C comes in parallel with the load via the transformer, so this inverter is called a parallel inverter.
Single Phase Bridge Inverter:Bridge circuits are commonly used in DC-AC conversion. Moreover, an output transformer is not essential in a bridge circuit.
Single Phase Half Bridge Inverter
Construction of circuit:-
Basically, for single phase half bridge inverter as shown in fig, the following components are required:-
- Two thyristors
- One voltage source (divided in two sources)
- Two diodes.
- A single DC source is divided into two DC Sources.
- Initially, two thyristors are not triggered to turn ‘ON’, so zero current flows through the device.
- The Thyristor T1 is turned ‘ON’ by giving a gate pulse it. The Thyristor T2 is kept ‘OFF’ and no gate signal is given to it.
- Thus, the ThyristorT1 starts conducting and the current starts to flow from Edc/2(positive terminal of 1st source)-T1-Load-negative terminal of 1st source.
- Thus, a positive cycle similar to that of ac cycle is obtained.
- Now, the Thyristor T1 is made ‘OFF’ and T2is made ‘ON’ by giving a gate signal to it.
- The Thyristor T2 starts to conduct and the current starts to flow through the load.
- The current takes the following path:-
Edc/2 positive terminal of 2nd source)-Load-T2-negative terminal of the 2ndsource.
- Thus, a negative cycle is produced.
- Two SCRs are triggered alternatively so that the load conducts current in both directions.
- Thus, a square ac wave is generated.
- Hence, direct current is converted into alternating current using inverter circuit.
- DC power source usage
- Uninterruptible power supplies
- In refrigeration compressor
- Portable consumer devices that allow the user to connect a battery, or set of batteries, to the device to produce AC power to run various electrical items such as lights, televisions, kitchen appliances, and power tools.
- Use in power generation systems such as electric utility companies or solar generating systems to convert DC power to AC power.
- Use within any larger electronic system where an engineering need exists for deriving an AC source from a DC source.
- “Power electronics” by M.D. SINGH, K B KHANCHANDANI