You need to build a DC-DC converter to get an isolated 350VDC bus.

You need to add an h-bridge on the 350VDC bus.

You need to drive this at 20kHz to 30kHz PWMed with 50/60Hz.

You need a filter on the output to remove all the high frequency harmonics.

For 15VAC you can: omit the DC-DC converter step and use the +/-10V to 13.2VDC for the input but be prepared for it cliping when the battery voltage drops below 11V and accept that it won't be isolated or build another DC-DC converter to give a stable 24VDC supply.

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Thanks a lot for replying. The output voltage (240v) will be rectified to DC voltage & then it will be again converted to 240V AC @50Hz. Since I only wanted to design a transoformer for the frequency 20-30KHz that is why I did not mentioned other details. The output volatages are:
Output voltage (1) : 240v Ac (3 Amperes)
Output voltage (2) : 15v Ac (3 Amperes)
while the input voltage is 10V to 13.2 (Center tapped)
with 40 Amperes current to deliver desired output voltage/current.
The core can be ETD 59 (3C8, 3C90, 3F3 etc). So please help me to mentione the turns ratio & wire guage for each winding.

 

Why do you want to do that?

You need a DC bus that's higher than the peak output voltage. The peak voltage of 240VAC is 340V which is why i suggested 350V.

I think you'll need a higher input current than 40A

Input power = 20*40 = 800W

Output power =
15*3 = 45W
+
240*3 = 720W
= 765W

This means your inverter will need to be 95.625% efficent which isn't likely.

I don't know the charicteristics of the core as you haven't posted the datasheet.

For 3A you need a crossectional area of about 0.5mm squared.

For 40A you need a very thick wire - it's better to use four 1mm squared windings in parrallel.

For 20V to 350V the turns ratio would need to be 350/20 = 1 to 17.5 but I'd use 1 to 20 because the losses will reduce the output voltage under large loads.

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Thanks again for replying! OK, I accept your modification in the design which is as under:

Output power (1)=350V.
Output power (2)=15V.
Output current (1&2)=3 Amperes
Input power = 10 to 13.2 VDC at more than 40A (as you suggested higher input current than 40A)

According to your calculation the efficiency is not possible 95.625% (agreed). I further requested by you to please provide turns ratio for all windings (primary & secondary) with the guage of wire. I'am attaching the datasheet of ETD59 Core (www.mag-inc.com).

It is once again stated that I 'll remain grateful to you since you are helping me to design the desired inverter.

Attached Files

2006_Design_Information.pdf (597.1 KB, 66 views)

 

I don't mind helping you but it seems like you're asking me to do all the work for you. The datasheet provides all the infromation you need for calculating the number of turns which is dependant on the frequency, the topology as well as the input voltage.

You've listed the input and output voltage as power for some reason. Also note that we're only talking about the DC-DC converter which is only half of the design.

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Firstly I'll pay special thanks for the quick reply. You are right in thinking that it seems I am asking you to do all the work for me. I know the datasheet provides all the necessary information but being a professional your expert opinion may help me to get highest performance from the required transformer

below is the design considerations:

Output power (1)=350V.
Output power (2)=15V.
Output current (1&2)=3 Amperes
Input power = 10 to 13.2 VDC at more than 40A
frequency =20KHz

Please oblige me by providing turns ratio for all windings (primary & secondary) with the guage of wire.

 

(sorry off-topic, but, Which city are you from in Pakistan?)

well....its a piece of cake to get the ratio for this core

 

I am from Karachi