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 12/120V inverter again
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Kiz1
New Member

Nigeria
4 Posts

Posted - Nov 23 2005 :  07:34:37 AM  Show Profile  Reply with Quote
quote:

(1) corncerning the inverter, can i use a 220v transformer in order to have output of 220vAC, and it has three Dc output wires(secondary side).
(2) The 2N3055 transistor i got was a metal-case type which has only two pins. Now i tested for the base and got that, but how do i know the emitter and collector? Are they both in the other pin? Please try to reply soonestly, i want to finish this project before the end of this month(November 2005). Thanks.





I wold use something smaller but not too small, not 2N2222. Something with 1A collector current at least.
As for resistors, I would think that as base current will be about 100 times less, you can try to increase R3,R4 maybe to 10K or more and get rid of tantalums. Try 1uF ceramics or film caps..

But that is only my guess, remember that! No responsibility on my part... use it on your own risk :))





Handel
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Kiz1
New Member

Nigeria
4 Posts

Posted - Nov 23 2005 :  07:36:19 AM  Show Profile  Reply with Quote
quote:

(1) corncerning the inverter, can i use a 220v transformer in order to have output of 220vAC, and it has three Dc output wires(secondary side).
(2) The 2N3055 transistor i got was a metal-case type which has only two pins. Now i tested for the base and got that, but how do i know the emitter and collector? Are they both in the other pin? Please try to reply soonestly, i want to finish this project before the end of this month(November 2005). Thanks.





I wold use something smaller but not too small, not 2N2222. Something with 1A collector current at least.
As for resistors, I would think that as base current will be about 100 times less, you can try to increase R3,R4 maybe to 10K or more and get rid of tantalums. Try 1uF ceramics or film caps..

But that is only my guess, remember that! No responsibility on my part... use it on your own risk :))





Handel
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Kiz1
New Member

Nigeria
4 Posts

Posted - Nov 23 2005 :  08:23:16 AM  Show Profile  Reply with Quote
quote:

I could not get the HEP 154 silicon diode, can you give me the substitute? can i use IN4007 as substitute? thanks



I do not think 60 V is not enough.. on that side of transformer you have only 12V of power, and diodes should protect from flyback voltage.. just a comment :)





Handel
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audioguru
Nobel Prize Winner

Canada
4214 Posts

Posted - Nov 23 2005 :  08:27:49 AM  Show Profile  Reply with Quote
Kiz,
1) Instead of guessing about pins for transistors, look at the labelled pic on the datasheet. www.datasheetarchive.com .
2) This project is too simple to operate properly. It needs Mosfets or paralleled output transistors and driver transistors to work.

To have a 100W output then the transistors must conduct 10A each from the battery, plus another 1A for R1 and R2. Therefore the current in the transistors is 11A each.
Resistors R3 and R4 provide only about 60mA of base current so the minimum current gain of the transistors must be 11A/60mA= 183. The current gain of power transistors drops at high collector current and the 2N3055 doesn't even have its current gain rated at 11A. Its minimum gain at 10A is only 5.0 and at such a high current it saturates with up to 4V across it.

3) You can try 1A power transistors to have an output of only 10W. But they and the capacitors will blow-up because the circuit causes their base-emitter reverse voltage to far exceed their absolute max rating, causing the junction to avalanch with very high current.
It takes a lot of power for one transistor to drive a high current into the other transistor that has avalanch breakdown. That power is deducted from the project's output power.



Edited by - audioguru on Nov 23 2005 08:36:45 AM
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tim
Mad Scientist

198 Posts

Posted - Nov 24 2005 :  6:46:51 PM  Show Profile  Reply with Quote
hey aaron do you know the minimum voltage to drive the gates of 34 paralled mosfet transistors 200v 18 amp

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audioguru
Nobel Prize Winner

Canada
4214 Posts

Posted - Nov 24 2005 :  8:21:08 PM  Show Profile  Reply with Quote
Hi Tim,
If you have a 100V or 200V supply, then why do you need an inverter?
You don't need a 200V-rated Mosfet in an inverter powered from only 12V.

Mosfets are much more efficient than old transistors in inverter circuits and their gate voltage requirement is shown on their datasheets. Most Mosfets need 10V on their gate for them to meet their current spec. Some Mosfets need only a few volts.

Mosfets have a very high gate capacitance and paralleling so many would require a huge current drive to the gates to quickly charge the capacitance. If the drive current is too low then the Mosfets will melt due to the long-duration slew-rate.

Assuming that the Mosfets are switching only half their rated current of 18A which is very low for modern Mosfets, 34 of them would cause a 306A current from a 12V battery that might cause it to blow-up, if it even has the ability to supply so much current. Wires the size of your thumb!

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tim
Mad Scientist

198 Posts

Posted - Nov 24 2005 :  8:33:20 PM  Show Profile  Reply with Quote
this circuit is for my electric truck and it uses 120 dc 400 amps and yes i use 2 gauge welding cable. this is a controller that has 34 mosfets. i bought the controller burned up but im making a new board caps mosfets and resistors but im going to use a 24 v 80 controller but only the pulse width modulater circuit to drive the mosfet gates.

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audioguru
Nobel Prize Winner

Canada
4214 Posts

Posted - Nov 24 2005 :  9:03:34 PM  Show Profile  Reply with Quote
48.000 Watts?
Look at what they do on diesel-electric locomotives.

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tim
Mad Scientist

198 Posts

Posted - Nov 24 2005 :  9:03:42 PM  Show Profile  Reply with Quote
hey kizl i worked on that inverter for 2 years and never really got it going the way i wanted it to work it worked but i GAVE UP.

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audioguru
Nobel Prize Winner

Canada
4214 Posts

Posted - Nov 24 2005 :  9:15:37 PM  Show Profile  Reply with Quote
Don't give up, over and over.
Didn't you see the 500W inverter that I heped fix?
http://www.electronics-lab.com/projects/power/033/index.html


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tim
Mad Scientist

198 Posts

Posted - Nov 25 2005 :  9:32:45 PM  Show Profile  Reply with Quote
well i guess all you electronic pros dont know about those mosfets. 34 in paralle shouldnt use much at all there all using the voltage at the same time. the 24 volt controller that im using for the pulse modulater has output of just under 12 volts and it used to push 5 24v 80amp mosfets in paralle.

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audioguru
Nobel Prize Winner

Canada
4214 Posts

Posted - Nov 26 2005 :  07:27:50 AM  Show Profile  Reply with Quote
Hi Tim,
Before you wanted an inverter to use 34 Mosfets so its output could make 120V at 400A which is 48,000W.
Now you are using only 5 Mosfets rated at only 24V?

When the inverter steps up a 12V battery's voltage 10 times, then the current in the Mosfets is also stepped up 10 times. That's 4000A!
Mosfets rated for only 80A would curl-up and die with 800A through each one.

Wait a minute. Is it the controller that uses 5 paralleled Mosfets to drive the gates of 34 power Mosfets?
I thought the quantity of Mosfets in the controller should have an even number so they can operate push-pull. Then they can quickly charge and discharge the huge gate capacitance of the many paralleled power Mosfets.

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tim
Mad Scientist

198 Posts

Posted - Dec 07 2005 :  4:05:38 PM  Show Profile  Reply with Quote
well its tim again this motor controller uses 34 mosfets rated 200v 18 amp each. all in paralle it handles 200v and over 600 amps. waiting for freewheeling diodes for coasting and the circuit is done including the pulse width modulator from a 24 v motor controller that im using.

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atul_jangle
New Member

India
3 Posts

Posted - Dec 13 2005 :  01:44:00 AM  Show Profile  Reply with Quote
HI all,
what should i do to build a invertor 40khz.
does the above ckt. will work as it is for me if i
change time constant of it only.

A.M.Jangle
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audioguru
Nobel Prize Winner

Canada
4214 Posts

Posted - Dec 13 2005 :  06:12:45 AM  Show Profile  Reply with Quote
To make a 40kHz inverter you will need a circuit that works, power Mosfets at its output that drive a special high frequency transformer that is probably bifilar wound on a ferrite core, a fast Mosfet gate driver IC and a power supply PWM driver IC.

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