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> Problem With Half Bridge Inverter Circiut
cranker
Posted: December 29, 2011 08:51 am
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here is the Inverter Diagram user posted image
I am Using IRFP450
but problem is that i am not Geting The 220V AC at Inveretr output ???
the Operating Frequency Of Inveretr Is 3Khz wacko.gif
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Geek
Posted: December 29, 2011 10:01 am
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QUOTE (cranker @ December 29, 2011 12:51 am)
here is the Inverter Diagram user posted image

Broken image and when I copy/paste the URL, I get:

QUOTE
You are not logged in or you do not have permission to access this page.


Please save to your computer and upload to Phootobucket or something wink.gif

Cheers!


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cranker
Posted: December 29, 2011 10:10 am
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Dnt Get !! What you are Trying to say ???
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Geek
Posted: December 29, 2011 10:17 am
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No one can see the image but you, because it's in your cache sad.gif

Cheers!


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johansen
Posted: December 29, 2011 10:40 am
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its a copy and paste from electrotechonline, you can see if if you're logged in.


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cranker
  Posted: December 29, 2011 11:17 am
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Ah thnkz Alot for Your help !!
i am New on this forum thats why !!
ok Here is the the Image

link removed

This post has been edited by CWB on December 29, 2011 04:01 pm
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Geek
Posted: December 29, 2011 11:25 am
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All I get are uncontrollable loops of ads at that horrible place (right through my blocker).

If anyone w/my email can download this, please send it to me and I'll host the image tongue.gif

Cheers!


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cranker
Posted: December 29, 2011 11:26 am
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here is the Complete Figure
i am Using 555 IC to trigger Irfp450 At 3KHZ
But the Problem Is that i am Not getting 220V At Inverter output
here Is another One Plz Check It
user posted image

This post has been edited by CWB on December 29, 2011 04:02 pm
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johansen
Posted: December 29, 2011 11:42 am
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are you trying to pwm modulate the half bridge at 3 khz to get 60hz out or.. what?

also, 555's might be useful for generating a square wave, but they are not appropriate for driving large mosfets.

you also need some dead time between the two mosfets to ensure they never turn on at the same time.


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cranker
Posted: December 29, 2011 11:46 am
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i am Just Giving 3KHZ Frequency to IRFP450 By 555....
And How to drive large mosfets?
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CWB
Posted: December 29, 2011 04:00 pm
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from the site listed in the link :
"*Note: Please Turn Off the Pop-up Blocker To Download the File!"
no way , aint gonna happen .
also , a google search shows that the site is a vector for mal/scumware .

@ OP :
in the interest of safety , i am removing the links from your post .
i don't believe that image shack is allowed here .
please use another hosting service that is "clean" ... photobucket is a good one .


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cranker
Posted: December 30, 2011 06:57 am
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here it is .
user posted image
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cranker
Posted: December 30, 2011 06:59 am
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user posted image

This post has been edited by cranker on December 30, 2011 07:03 am
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johansen
Posted: December 30, 2011 07:24 am
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google half bridge driver.

the reason your circuit doesn't work is because there's no provision to lift the gate of Q2 5 volts *above* its drain, when it turns on.


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cranker
Posted: December 30, 2011 05:49 pm
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Thnkz for Ur reply !!! johansen
can u Plz tell me how to Resolve this ????
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Sch3mat1c
Posted: December 30, 2011 08:03 pm
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Exactly as shown in the diagram:
1. You have a +/-105.5V supply on the half bridge, according to the voltmeter; however, this should probably be closer to 320V if I understand your source correctly. The reason for this is apparent...
2. V1 appears to be 20V, which is too much for a 555 (15-18V max), and close to the limit for MOSFET gates (20-30V absolute maximum).
3. I can't tell how all the grounds come together because your schematic capture program does not draw junction dots at this scale. I can only assume that V1 pin 2, 555 pin 1, C2 pin 2, C1 pin 2 and Q1 emitter are all connected to ground.
4. The drive is terrible -- Q1 will turn off very slowly if at all. Even if it turned off quickly, Q3 will turn on very slowly due to the large value of resistance (R3) supplying it. A high current driver is required to operate IRFP series transistors. The drive to Q2 is not as critical, because the 555 will supply 200mA peak at its output; it could still use improvement however.
5. This doesn't matter any, because Q2 will always remain in the linear range, rather than switching.
6. More importantly, Q3 will explode instantaneously due to the 105-125V gate voltage applied. The simulation doesn't realize this and goes ahead computing the impossible. Most likely, Q3 is turned on very hard (and never switches off), also turning on Q2, carrying a large current, pulling the high voltage supply down to 211V.

Please don't even attempt to simulate, let alone build, a circuit that you do not understand. This circuit effectively has multiple ground references. Until you understand how a transistor "sees" an input voltage, I suggest you work with low voltage, single ground circuits. Do not EVER attempt to build a circuit like this, as (if the schematic AND simulation weren't enough of a clue already) it will spark, burn and explode without any hint of operation whatsoever.

Please *DO* get some hands on experience with a breadboard. Keep it under 20V and 1A. You will destroy transistors and resistors, but they aren't likely to blow up in your face and blind you, or shock you with line voltage.

For a good starting point, you can try a circuit like this:
http://myweb.msoe.edu/williamstm/PWM_Gen_Schematic.pdf
I suggest IC1 = LM393, rather than the TLC3702 shown. The output transistors (Q6-Q9) can be any MOSFET, but I would suggest IRF540 for starters. If J5 is supplied with 18V as shown, the output can be supplied with up to 12V (between J1 and J2). Note that J2 shares a common ground with the 18V supply. The outputs are complementary square waves, because this inverter contains two half bridges, making a full bridge, or h-bridge.

If you supply a higher voltage to the output, the "top" transistors (Q6, Q8) won't fully switch on, causing them to heat up, and causing the output to fall short of the supply voltage. You will get correct performance when the output supply is greater than 0V, up to 5V less than J5.

The drive circuit used here is a little complicated, which should be entertaining to explore with an oscilloscope. It provides weak drive, causing the transistors to switch quite slowly. This works best at audio frequencies (under 10kHz), which is where the oscillator operates (frequency is controlled by R6; duty cycle is controlled by R8 from 0 to 100%). To operate at higher frequencies, a more powerful drive circuit is required.

Tim


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cranker
Posted: December 31, 2011 09:20 am
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thank U so Much TIM for ur Reply its really helpfull ....
i Am trying to built An INDUCTION FURNACE ,
so here is a new diagram which i built from ur Advise ....
plz let me know if it is right or not ???
it is Giving the desired output ....but the Waveform is not Understandable
user posted image
and Waveform
user posted image

This post has been edited by cranker on December 31, 2011 09:22 am
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johansen
Posted: December 31, 2011 01:13 pm
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i can't read the type under whatever driver you selected, but i have a feeling that a fan73xx isn't rated for 300 volts.

that said, for 3 Khz 100 ohm gate resistors are probably going to kill those mosfets.

You should avoid simulating this stuff and start bread boarding it. when you can melt a pencil eraser amount of aluminum or solder in an induction heater for 10$ in parts, then move on to rectified mains and such..

3 Khz is really slow, unless you intent to melt 10 tons of steel.
what is your budget?
The reason I ask is the capacitors you need for the work coil aren't free, and are often just as expensive as all the components you attempted to simulate, (when paid for in single quantity on digitkey)


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cranker
Posted: December 31, 2011 01:15 pm
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Hi tim !!
i have made the circiut u have Told me
here it is
user posted image
but The problem is this
http://i1026.photobucket.com/albums/y325/cranker117/2.jpg
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cranker
Posted: December 31, 2011 01:18 pm
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Thank johansen !
Its FAN7385 ....it can be operated upto 600V
http://www.fairchildsemi.com/ds/FA/FAN7385.pdf
plz u tell me What IC can i used For GATE DRIVER ???
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johansen
Posted: December 31, 2011 01:32 pm
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QUOTE
plz u tell me What IC can i used For GATE DRIVER ???


to be honest, the gate driver is of no consequence, you can do it with a gate transformer and 4 2n2222 transistors and 4 diodes..but again, such knowledge will not come from simulating this stuff in a classroom.


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cranker
Posted: December 31, 2011 01:39 pm
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Yup !!! Agreed
Can u Tell me johansen , how to Start This Project on Breadboard ???
and How to make Gate Transformer
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Posted: December 31, 2011 01:46 pm
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QUOTE (johansen @ December 31, 2011 05:32 am)
...such knowledge will not come from simulating this stuff in a classroom.

Nope! Comes from letting the magic smoke out on a bread board and figuring out what went wrong. That's *true* wisdom.

Cheers!


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cranker
Posted: December 31, 2011 01:48 pm
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hahahaha True !!! Geek
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Sch3mat1c
Posted: January 01, 2012 05:10 am
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Try adjusting your simulation settings:

ABSTOL = 1e-9
CHGTOL = 1e-12
GMIN = 1e-8
ITL5 = 1e4
PIVTOL = 1e-6
RELTOL = 1e-3
RSHUNT = 1e8
VNTOL = 1e-3
Select integration mode GEAR (sometimes labeled RK2).

If these don't work, play around with values until it does. Also, double check the circuit. Junction dots again didn't show up so I can't tell if your circuit is correct.

Tim


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