250 watt smps based inverter

[--BawA--]

Hello everyone,
I am designing a 250watt smps based power inverter of following configuration
Input 12VDC
Output 220VAC
Frequency 50Hz
Waveform -Modified Sine Wave

In my DC DC converter stage I intend to use ETD34 core @100KHz. i will use a Push-Pull topology .

1) Will this transformer be able to deliver 250 Watt continuous power?
2) Is there any harm of using 100Khz frequency for Push-Pull topology or should i use a lower one?

 

[ashugtiwari]

I could not find the proper spec sheet for transformer which determine the power or voltage current rating of transformer. I also could not find the turns ratio. If u know the cross sectional area of input and output coils with their length, the resistance of coils can be found. Using these values u can determine the VA rating and with power factor of 1 to 0.5, u can find the power output. If possible plz share the spec sheet for transformer, i just found diagrams on google. But u can refer here for finding the watts: https://answers.yahoo.com/question/index?qid=20120419093002AAgdEQb

The PWM frequency depends on the MOSFET switching frequency, switching losses, transformer rating from spec sheet. If the PWM frequency is too high, the MOSFET switching losses will be high and so the more heat will dissipate in MOSFET, the switching losses. Also, the transformer core will also get heated if very high frequency is used since more discontinuous currents in coil can rise AC losses. If the PWM frequency is very low, the transformer coil can saturate which result in no induction at secondary side i.e. having no output. To find the PWM frequency, find the MOSFET switching frequency from MOSFET datasheet, use it as starting point for PWM, then find the transformer primary coil inductance, and resistance to find primary coil time constant, keep ur frequency higher than this to prevent saturation, check the magnetic hysteresis freq of core. Average all these values to find the PWM frequency.

I usually do some trial and error after finding the answer to reduce the MOSFET and transformer heating.

This is quite theoretical, but i hope it helps. If possible plz share spec sheet.

 

[thannara123]

Me also trying for that

 

[BradtheRad]

Waveform -Modified Sine Wave

Can you confirm this is the shape of waveform you want?

https://rimstar.org/renewnrg/sp_pure_true_modified_sine.htm

 

[--BawA--]

Can you confirm this is the shape of waveform you want?

Yes, the link that you attached has image of modified sine wave , its like a square wave with three levels + , - and 0.

 

[--BawA--]

If my DC DC stage is regulated , Is it necessary to have a feedback loop in DC AC stage also, ? why or why not?
I am using TL494 for driving H-Bridge .