The post discusses how to convert 3 phase AC to single phase AC through a special bridge rectifier at any desired voltage. The idea was requested by Mr. Chaquito
The Circuit Request
Dear Home-made Circuits,
You have a very nice page and I find it really good, If been looking for a 380V 3ph converter to 230V, it should with held at least 3-5 KVA. Not sure if you have one or
would you be able to direct me to one.
I have a 3ph input of 5.5KVA from a generator that I would like to convert to one single output of 230V +- 3-5 KVA. Doing the usual ph to neutral per ph would not give me a strong KW output. Transformers are very expensive.
I would appreciate your help thank you.
The Circuit Design
The question how to convert 3 phase AC to single phase AC can be solved by first rectifying the 3 phase AC to DC and then converting the DC back to 220 V AC through a full bridge driver IC and H-bridge mosfet network.
The first stage intended for converting the 3 phase AC to DC may be executed simply by the traditional diode bridge network, as may be witnessed in the following diagram. After filtration this would produce a peak of 530 V (with a filter capacitor of around 10uF/1kv included across the load)
Now, once the 3 phase rectified DC is achieved, this will need to be converted to the desired single phase AC, as per the request this value should be 220 V.
A full bridge mosfet driver topology may be incorporated for implementing the above requirement, as shown in the following diagram:
The layout looks simple and easy to configure, however it would produce and subject the load to the full 530 V instead of the specified 220 V.
The issue can be normalized and controlled to the desired levels through an external voltage sensor circuit, which could be further integrated with the Ct pin of the IC IRS2453.
The simple solution can be implemented by incorporating the following circuit:
The 220k preset is adjusted precisely so that the transistor just begins conducting at voltages around 240 V across the load.
When the transistor conducts, the Ct pin is grounded at that instant, forcing the IC to inhibit its oscillations which in turn renders the high side outputs to go low, cutting off the rectified high voltage to the mosfets.
This results in lowering down of the voltage across the load which allows the BC547 to switch OFF and restore the IC operations....the procedure repeats making sure that the output stays under control and at the specified 220 V level.