an emergency project i need help

hi everyone,i have some project and i need help with if u can help i will be grateful to all of u;the project is a very popular one but i am not familiar wid it it is as following;
In this project, you will design and implement a DC to three-phase inverter.
In other words your circuit will generate three-phase alterna g current from
a DC power supply,the available components for us is transistors transformers opamps ua 741 only high power resistors capacitors not likely but we can use inductor better not but if we must yes,but we need at least %25 efficiency
if everyone has done a similar project or if anyone can help me i will be grateful thx waiting ur mails bye thx

What's the emergency? The 741 is over 100yrs old according to audioguru

maybe its centenary celebrations are imminent ...

The vacuum triode's 100th was last year. I think the 741 has a ways to go for the century mark.

it means that i need help and quickly about that project i wrote

theking2725 said:

it means that i need help and quickly about that project i wrote

Click to expand...

We know what the word "emergency" means? What they're asking is "why is it so urgent?"

Why is it so urgent? It just looks like a school assignment to me.


Torben

o yes its my labarotary project ,for sure and i have some ideas but i couldnt collected them first step is to get i think 3 square waves wid approximately 120 degrees difference but i dont know how this circuit is constructed , after i think there should be some filtering to get sinusoids but for example i dont know where to use the transistor i guess it is for increase the efficieny well,it will be grateful that u help me thx

theking2725 said:

hi everyone,i have some project and i need help with if u can help i will be grateful to all of u;the project is a very popular one but i am not familiar wid it it is as following;
In this project, you will design and implement a DC to three-phase inverter.
In other words your circuit will generate three-phase alterna g current from
a DC power supply,the available components for us is transistors transformers opamps ua 741 only high power resistors capacitors not likely but we can use inductor better not but if we must yes,but we need at least %25 efficiency
if everyone has done a similar project or if anyone can help me i will be grateful thx waiting ur mails bye thx

Click to expand...

exept for the first and last sentence it looks more like a tender document for a job

what did the teacher explain you already so far??

the aproach i would have is make a oscilator and delay and separate the signal so that you have 3 signals that are shifted 120 degrees from each other and feed that in a push/pull circuit that feed the 3 diferent transformers

Robert-Jan

theking2725 said:

o yes its my labarotary project ,for sure and i have some ideas but i couldnt collected them first step is to get i think 3 square waves wid approximately 120 degrees difference but i dont know how this circuit is constructed , after i think there should be some filtering to get sinusoids but for example i dont know where to use the transistor i guess it is for increase the efficieny well,it will be grateful that u help me thx

Click to expand...

first make a block diagram where each part of the circuit is represented than look block for block to make it
Block one: oscilator
block two: splitting signals and delay them from each other
Block three: push/pull circuit and transformer


Sucsess
Robert-Jan

ok i will try and simulate your suggestions on ewb i hope i can be successiful

hi again

for getting the three phase square wave part with 100hz frequency,using capacitors and 741 op amp and sure resistors what is the circuit schematic i can use can any one help and send me or attach me a schematics my mail is theking2725@yahoo.com if someone help i will be grate ful

Now you tell me you want 100 cycles/sec.

Well this circuit is not a working diagram, just a starting point.

I would be inclined to get the osc transistor running first, the caps
are not electrolytics.
If you want them to be electrolytics, then you will have to re-arrange
the circuit.
As it stands, the adjustors are simply to equalise the three outputs.
Those outputs as drawn are not intended to give much output, that would
have to be further amplified after it is shown to be working.

As required, there are no inductors,
except for the three small output transformers.

Best of luck with your assignment, John

hi john

john i am grateful to your design but u know i need to use capacitors andmost important is the ua 741 op amp do u have such a design or anyone else thx a lot
buddies

The lousy old uA741 opamp is 40 years old. It might be fine in an inverter circuit.
I think the 3rd world and 5th world are getting it now. The 4th world gets it next year.

Your teacher told you to design the circuit, not ask us to design it for you.
So design a phase-shift-oscillator with an opamp. Google for Phase-shift-oscillator Circuit then copy one.

Offtopic

audioguru said:

The lousy old uA741 opamp is 40 years old. It might be fine in an inverter circuit.
I think the 3rd world and 5th world are getting it now. The 4th world gets it next year.

Click to expand...

OFFTOPIC: hahaha 741 opamp just arriving here!? I admire very much your experience, and appreciate the number of times you got me out of trouble, Audioguru. But I really dissagree the repetitive commentaries that you make about first, second, third, four, five, twenty, one hundred world. It's a very unreal clasiffication, on social topics but also electronics.

I'm not living on a "first" or "second" world country, but I can get any kind of electronic component at a rasonable price or even cheaper, on any electronics store. I'm making the comparison with San Francisco CA, where I also lived.

Even better, is much more easier to find qualified technicians and spare parts, because the idea of "Use and if damaged, simply throw away" is not so common than on the first world countries.

I don't know about poorer and less fortunate countries, but generalizing is not a good thing. As fake as "Africa is only wild animals, Australia Kangaroos, Russia snow"

I hope you take this suggestion on a positive way

The "lousy 40 year old 741" is still in volume production with at least 5 major manufacturers. If it meets your needs, use it.

The last time I looked, parts of Columbia are modern.
The school kid is making a circuit with a 40 years old opamp so either he is in the 5th world or his text book is 30 years out of date, but I said it is fine in his simple circuit.

Many countries make electronic parts that are not available there.

here a mesage from the 5th world

741 has landed opto couplers expected nexts 4 months

but PIC's are still smugled into the country and the rumor is that it's still prohibitive to own a PIC although they wan't to losen up a bit because of improving the comercial compatitive ranking with other countrys

still only hardware will not do the trick but you can't say that loud unless you're a NGO

still than they don't provide schooling also so why telling it and watch it go wrong

i am busy in the mean, evil and hard comecial sector (from an NGO point of view)

but i know i make a change i do teach my coleuges things in a trade where there is not even an school for in this country

so if our company is sucsessfull in the comercial world (and it is) we are moving the standards up

back to topic

it's a pain to get some desent components here and it's sometimes realy a challenge to get something done but after all if you get it done the satisfaction is bigger

so before we start to burn a old solution/shematic down (that is already replaced by better ones long time ago)have a thougt about the situation a person is in , it might be the only thing he can make

Robert-Jan

I like talking about new high-tech parts, not old antique parts.
Maybe there is a website in a 5th world country for talking about old stuff.