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I'm building a specific circuit I found here: http://makingcircuits.com/blog/2015/07/48v-inverter-circuit.html

Part 1:

I'm pulling my hair out trying find a transformer like the one shown in the diagram. I'm pretty new to building circuits from diagrams, so maybe I've got this wrong, but it seems to be asking for a for a type of transformer which is grounded in the middle of the primary coil. Specifically it's asking for a 36v-0-36v 1000VA transformer. Is this a specific type of transformer? If so, what is it called? Please provide a link if you are able to locate one, some alternative solution,... or a correction for my misunderstanding.

Part 2: Also, I've modified the inverter to provide 400Hz rather than 50Hz... and I would like to get approximately 570V from the secondary coil... But I would settle for less. Should I just wind my own transformer? Regardless of this question, I still need the information in Part 1 answered.

Thank you

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2 Answers 2

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The transformer they describe in your project is a 240 V to 36-0-36 V and they use it backwards. They drive the secondary and use the primary as the output

So the circuit drives what would conventionally be the output winding, and the output is what would conventionally be the input mains winding.

In addition, since you want to run the convertor at 400 Hz you will be able to get away with a somewhat smaller transformer VA rating. At 400 Hz you need less Iron, but there is still a limitation imposed by the wire (windings) current capability too. I'd suggest that for 1 KVA @ 400 Hz you may get away with an 800 VA transformer rated at 50/60 Hz.

This type of transformer might be used for very large audio amplifiers, though an 800 W amp is pretty big these days.

Digikey showed only one transformer in your requirement range: http://www.digikey.com/product-detail/en/triad-magnetics/VPM48-20830/237-2061-ND/5721780

The datasheet shows this configuration may be possible:

enter image description here

You'd have various options to select an output voltage available.

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It's commonplace for a transformer to have a winding described as x-0-x, the 0 terminal is simply a centre tap. This makes a full bridge balanced output about ground easy to acheive. When used as the primary in an inverter, the centre tap will typically be wired to the +ve terminal, with either end pulled down to ground.

A 'normal' mains transformer core will be very lossy at 400Hz. These things are built down to a price, for a specification. Good low loss operation at 400Hz, as in aircraft transformers, requires very thin (expensive) iron laminations. The lams used for 50/60Hz transformers are much thicker.

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