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How Inverter Work

Time:[2016-11-26]     Views:207

How can an inverter give us a high voltage alternating current from a low voltage direct current?


Let's first consider how an alternator produces an alternating current.In its simplest form,an alternator would have a coil of wire with a rotating magnet close to it.As one pole of the magnet approaches the coil,a current will be produced in the coil.This current will grow to a maximum as the magnet passes close to the coil,dying down as the magnetic pole moves further away.However when the opposite pole of the magnet approaches the coil,the current induced in the coil will flow in the opposite direction.


As this process is repeated by the continual rotation of the magnet,an alternating current is produced.





Now lets consider what a transformer does.A transformer also causes an electric current to be induced in a coil,but this time,the changing magnetic field is produced by another coil having an alternating current flowing through it.Any coil with an electric current flowing through it will act like a magnet and produce a magnetic field.If the direction of the current changes then the polarity of the field changes.


Now,the handy thing about a transformer is that,the voltage produced in the secondary coil is not necessarily the same as that applied to the primary coil.If the secondary coil is twice the size (has twice the number of turns) of the primary coil,the secondary voltage will be twice that of the voltage applied to the primary coil.We can effectively produce whatever voltage we want by varying the size of the coils.






If we connected a direct current from a battery to the primary coil it would not induce a current in the secondary as the magnetic field would not be changing.However,if we can make that direct current effectively change direction repeatedly,then we have a very basic inverter.This inverter would produce a square wave output as the current would be changing direction suddenly.




This type of inverter might have been used in early car radios that needed to take 12 volts available in the car and produce the higher voltages required to run radio valves (known as tubes in America) in the days before transistors were widely used.


A more sophisticated inverter would use transistors to switch the current.The switching transistors are likely to be switching a small current which is then amplified by further transistor circuitry.This will still be a squar wave inverter.