I am working on unipolar Inverter Scheme. I did MATLab coding and implemented on microcontroller. Now I want to step-up the output up to 220 volts.
My question is that, What type of transformer should I use ?
Hello Ghazanfar Ali,
for practical purposes, there is a problem: If your circuit remains unmodified, and you just insert a transformer between the output and the load, then much of the input power to the transformer is located at 50 Hz. Consequently, you cannot use one of these nice tiny transformers as found in switching power supplies but you have to use a bulky one suitable for 50 Hz. To make things worse, a considerable part of your power spectrum is located at higher frequencies, so a core made from insulated sheets of iron intended for use at 50 Hz will cause considerable losses. Thus, you had to provide a bulky transformer equipped with a ferrite core! It will be large, heavy, and expensive!
If this is just an experiment, I would try both sorts of cores (with very low power delivered to the load), and look carefully at the results. If it is intended to really work, I would redesign the concept. Rough sketch:
Generate a bipolar high-frequency output voltage whose pulse width is modulated with 100 Hz (plus some harmonics of 100 Hz in order to make the envelope of each 100 Hz full wave look roughly like a 50 Hz half-wave (apart from the DC offset)). The pulse width modulation should effectively result in a symmetrical amplitude modulation. This results (after some filtering) in a narrow frequency band around your high frequency (just like AM radio waves). Feed this voltage into a (tiny :-) transformer with ferrite core, and place behind the transformer two controlled rectifiers which you can switch on and off in a complementary way. So, the rectified = "demodulated" (and perhaps filtered) 100 Hz waves will reach the load with alternating polarity, resulting in 50 Hz.
Be careful to isolate the controlled rectifiers from your microcontroller (e. g. by employing optocouplers); otherwise an error or a defect could cause the output voltage to damage your controller plus even your computer if it is connected to the controller.
Hope this helps.
Hi,
It depends upon the frequency level of input voltage. If it is of high frequency(> 1KHz) and we are using normal iron core transformer, then the core saturates easily, which will heat up the winding.So in this case you have to use ferrite core material, otherwise for low frequency transfer use iron core material.
Thank you Debasish Mishra
Actually in above attached picture, I have used 3000 Hz frequency of triangular wave.
depending upon the switching frequency and the frequency of the fundamental you can use a regular 50 Hz iron core transformer.
Sir, Thank You for your kindness.
I wanna detail you, that when I filtered above attached picture, then I got results attached below. Now what should I do ?
With your filtered output signal, you can certainly use an iron core transformer. But if the maximum power you want to deliver is, say, above 50W, your device will become larger and heavier than it necessarily has to be.
How bulky the transformer has to be depends on the maximum power it should transmit. If you would design your own transformer from some kind of transformer kit, you could start by calculating the maximum effective currents in the primary and in the secondary winding. The next step is choosing the areas of the cross-sections of the wires; to be on the safe side, there should be not more than about 2.5 A per 1 mm2; for poorer performance, you can go up to 4 A/mm2. (In wiring for power distribution, you can have easily 10 A/mm2 but there the heat flow from the wires to the surrounding crosses a much larger area.)
For given wire cross-sections, a small cross-section of the core and a small number of turns per winding would yield short wires and hence small ohmic losses. But on the other hand, the current in the primary winding is (only very roughly due to phase difference) the sum of the current necessary to provide the output power and the current caused by the impedance of the primary winding. Additionally, you must not drive the core into magnetic saturation. These aspects enforce a certain number of turns of the primary winding on a core with a certain area of cross-section. As a consequence, the number of turns of the secondary winding as well as the cross-section of both windings together is given.
Here you can see the advantage of (moderately) high frequencies: You need wire of about the same cross-section but considerably less turns because the impedance of the primary winding would increase proportionally with increasing frequency if the permeability of the core would be independent of frequency (which it is not, unfortunately).
thank you sir for your guidance. I got the exact answer. this will be lengthy process for my project. I am leaving this step-up part.
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