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shivick21
Apprentice
Philippines
57 Posts |
 Posted - Dec 17 2004 : 12:59:10 PM
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maloy,
whoa... nice one! great! but now i am confused.. coz you said that ur using the "original project", so what "original project"? heheh coz there is one posted in this forum called 500w inverter design" and the one's that aaron's posts on his project list. and also.. im a noob. i ive try to make one and exploded."whow" so i stop. now im willing to make a new ver. that you develop.
Audioguru,
elow.. still messing around with this project? hehehe.... i have a question.... is there is other subsitute on 2n3055? i cant mold this thing on the heatsink w/o shortcicuiting others around it. i need a 3 pin transistor. not a 2 pin based transistor.(eg.... the one like a button. sorry im only a noob. hehehe  i want to reposition it around the chasis but the scematic tells me that i cant position the 8 transistor on one big Heatsink. and also, a new data sheet on this project. Please post a link! hehhehe
IMO can you just break one ups and take all the parts out and study it? coz it may have give u or us a sights on this thing nee? i know that buying expensive ups gives u a pocket headache but when u came up on it, its worthfull coz u can now build a working ups/inverter w/o exploding it like a popcorn.
so gud luck on to it guys and wish me a bunch of luck 2!! i hope that my house wont set on fire while im working on this. heheh chow guys!!! thanz!
Aki-kun "Pls! tank me! Im a noobs" |
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maloy
Apprentece
6 Posts |
Posted - Dec 17 2004 : 3:34:47 PM
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hi Audioguru, you said that my capacitors are big to withstand current, really they are very tiny , less than 1cm long, ok contact me on my email and I'll send you photo of my device inside
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audioguru
Nobel Prize Winner
Canada
4218 Posts |
Posted - Dec 17 2004 : 8:04:01 PM
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Hi Noobs,
It sounds like you didn't use insulating mounting washers on the output transistors and driver transistors in your 500W inverter.
Did the transistors blow-up to protect the fuse?
I've seen 2N3055T transistors in a button package (TO-220) with 3 leads, but they can dissipate only half the heat that the regular TO-3 package can.
We have been talking about Aaron's project lately.
Hi Maloy,
I've seen non-polar 47uF/50V caps. I am amazed they don't get hot with nearly half the inverter's power going through them to breakdown the inputs of the transistors.
I am also amazed that the transistors conduct 9A with only a small base current from the 180 ohm resistors.
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maloy
Apprentece
6 Posts |
Posted - Dec 18 2004 : 05:26:15 AM
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Hi Audioguru, just tell me do you believe me or not?
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audioguru
Nobel Prize Winner
Canada
4218 Posts |
Posted - Dec 18 2004 : 11:06:03 AM
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Hi Maloy,
It is extremely difficult to believe you. Many others have tried non-polar capacitors and paralleled 2N3055 transistors in this inverter without success. There was another forum about its problems before this one, so this one is called, "again". Others have posted separate topics about it, instead iof posting properly in this topic. This inverter even has the same problems on another web-site where it is posted as a project!
You don't tell us how much current it is drawing from your battery and the actual battery voltage when it is producing "100W" nor how you determined that it is actually producing 100W.
The numbers required just don't make sense.
Assuming a 12.0V battery (yours may be fully-charged at about 13.5V), a 100W load will draw 8.33A from it. The inverter isn't perfect and will heat-up so will draw even more current, maybe 10A total.
The inverter's transistors must conduct the 10A through the transformer, alternating. With your transistors paralleled each must conduct 5A.
The 2N3055's datasheet says that its maximum current gain at only 4A is 70. Typically the gain is 35 and its guaranteed minimum is only 20 at 4A. It is less at 5A and less again when saturated (fully conducting) because the current gain is spec'd with 4V across the transistor. The current gain is typically only 20 at 5A when saturated.
Therefore each transistor typically needs the 5A load current divided by the 20 gain which equals 250mA of base current or 500mA for both when paralleled. Transistors are normally driven with twice as much base current (Ic/Ib=10) to ensure good saturation.
But the 180 ohm base resistors will have a maximum of 11V across them and therefore can supply only 61mA (11 divided by 180), which is only 1/8th of what is needed.
Sorry Maloy, other people have tried the same as you and it didn't work for them, the numbers disagree with you and therefore I don't believe you.
Wait a minute. Maybe your transistors are actually cascaded, not paralleled, like the darlington connections in the successful 500W inverter. The current gain will be at least 400 and it will work well at 100W, if you also protect the bases from the negative over-voltage of the capacitors. We have discussed such an arrangement but nobody tried it. Maybe you did.
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audioguru
Nobel Prize Winner
Canada
4218 Posts |
Posted - Dec 19 2004 : 8:55:16 PM
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Hi Maloy,
I just got an e-mail from Evgeniya, is that you?
You sent some nice pics of your inverter driving a 75W bulb brightly.
My deepest appologies to you, you did get the thing to work!
BUT! I see in the pics a huge heatsink and equally large fan blowing away your inverter's massive heat. I figure that since the transistors don't have enough current gain, they can't saturate properly and probably have 6V or more across them while they are conducting 12.5A or more. Their resulting 75W or more of heating is a terrific waste, with the battery delivering 150W or more to light only a 75W bulb. Of course with a 100W load the heating and waste is much more.
You were clever to re-wind your transformer so it works well with the reduced input voltage of only about 6V, instead of 12V.
I would never think to do it your way.
Thanks again for the e-mail.
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audioguru
Nobel Prize Winner
Canada
4218 Posts |
Posted - Dec 19 2004 : 9:07:04 PM
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Malory, hi again.
I just thought about your capacitors.
Of course! With your transistors operating at only 6V, they never breakdown and keep the capacitors happy and cool. Clever of you again.
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maloy
Apprentece
6 Posts |
Posted - Dec 20 2004 : 07:48:37 AM
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Hi Audioguru. thanks for your reply, I really appreciate your opinion about my devise. So lets discuss some details ; your mentioned huge heatsinks and fan and excessive heat that could be produced by device. Ok those heatsinks are not so huge; they came from an old computer power supply and I used them because they were only available ones in addition I use them as a conductors to deliver collector current to transformer thus my transistors are not insulated from radiators. in my first version I used 2 transistors and yes they were getting really hot and were not powerful enough to even excite any transformers at all.so as I said previously the solution is increased thickness of conductor(the thinner conductor the more heat is produced ,mechanically it is like excessive pressure in tiny piping, solution is to increase the diameter of pipe so those rules equally acceptable for any sort of conductors regardless of what it is piping or wiring) . My inverter can operate without the fan but this idea I took from the inverter I saw on the shop shelf . about capacitors ; I already mentioned that my capacitors were under influence of sudden explosion thus I had tried countless number of tantalum ones and some amount of different electrolytic ones , they were rated from 20v up to 350v BUT DC ones and all of them ended in a trash as soon as they reached their boiling point just think 350v capacitor that designed to withstand continious 240v in computer power supply , my ones is 50v tiny caps BUT for AC current , I don,t know how you calculated the voltage my capacitors are operated at but if there only 6v (and I believe you) that mean those 6v are totally responsibly for all capacitors that exploded worldwide after being installed into circuit of inverter people trying to get running .In my opinion there is not a lot of current driven through capacitor-resistors area ; we have got some sort of feedback of positive current through resistors to bases of transistors and capacitors in this case acts as receivers of positive and negative charge at exchange , all of this allow transistors work in resonance or to be on and off after each other, simply they act like mechanical swich that allow the current run through different windings of centretaped transformer when you have positive continuous current at center of transformer and negative one runs in different directions through 2 windings after each other towards one common positive center, thus we' ve got replication of AC in the rest of transformer.If you look at this inverter curcuit closer you will notice that positive current is supplied into transformer directly without any resistance of electronic armature.and for the negative onethe transistors is the only resistanse accordingly to schematic the current must pass through emmiter to collector (I use heatsink as collectors' conductor) and then to the transformer winding. Those 10ohm resistors are suppliers of negative pulses to the switch capacitor assembly that's why we have some sort of alternative current in this area and as result those heaps of innocent capasitors that were executed so violently.
What do you think about it all?
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audioguru
Nobel Prize Winner
Canada
4218 Posts |
Posted - Dec 20 2004 : 09:21:11 AM
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Hi Maloy,
1) A short fairly thin wire can easily pass only 10A very well.
2) The capacitors with the 10 ohm resistors don't "feed a negative pulse to the switch capacitor assembly". They protect the transistors from high-voltage spikes caused by the inductance of the transformer especially when the load is suddenly removed or turned-off.
3) With only 6V available because the transistors don't have enough current gain nor drive to saturate properly, the switch capacitors have a very low current when charging and discharging from the 180 ohm resistors.
But when the supply voltage increases above the breakdown voltage of the transistors' base-emitter junction (about 7V), the current in those capacitors is enormous and continuously pulsing. Each capacitor has a powerful collector driving one end and the "dead short" of a base at breakdown at its other end.
I think your capacitors will blow-up too, soon after removing or turning-off the load.
Otherwise, the manner you wound your transformer creates a continous load and you are very lucky!
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ofussyjoe
Apprentece
Nigeria
5 Posts |
Posted - Jan 13 2005 : 6:00:35 PM
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| I'm a student in school. I'm looking for beginner projects that could help me to study in school. I built the FM transmitter on Aaron cake succefully and I worked out. I want to build a voltage regulator for DC voltage, I got some curcuit diagrams online but I've not started cos I want to analyse the circuit. I also want my next project to be AC voltage regulator. I've been thinking on how to do this, I've been some circuit that could just regulate ac voltage directly from the ac mains but I couldn't get. So I thought if it's possible to step down ac to dc, regulate dc voltage and step up the regulated voltage, I don't know if it's going to work. Could anyone pls give me some guidelines on how to go about all this |
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audioguru
Nobel Prize Winner
Canada
4218 Posts |
Posted - Jan 13 2005 : 10:10:15 PM
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Hi Joe,
You can't just simply feed an inverter with a regulated DC voltage and expect its AC output voltage also to be regulated. The inverter's transistors, transformer and even its fuse cause an output voltage loss that varies with the amount of load. Besides, the DC voltage regulator would be passing a high current and would therefore get very hot (a waste of power).
You must use feedback to detect that the loaded output voltage is dropping and to cause a boost in the input voltage.
You could use an efficient switched-mode voltage regulator to feed the inverter and use feedback to adjust its voltage.
You could also use an efficient switched-mode inverter, whose output voltage can be regulated by feedback, and even produce a perfect sine-wave output (the other simple inverters have a square-wave output).
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ofussyjoe
Apprentece
Nigeria
5 Posts |
Posted - Jan 14 2005 : 6:03:06 PM
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I got everything you said but maybe not perfectly well. You seem to forget that I'm a student and that I'm just a beginner. You mentioned switch node voltage regulator, switch node inverter, what does all that seem to mean. I'm sorry but could you pls come a little bit lower to my level. Should in case this forum is not fit for that you could mail me (ofunsoje@yahoo.com). Thanks for the contribution
ofj |
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audioguru
Nobel Prize Winner
Canada
4218 Posts |
Posted - Jan 14 2005 : 10:07:10 PM
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Hi Joe,
Switched-mode uses Pulse-Width-Modulation to vary the duty-cycle of power supply pulses that are applied to a load. You could learn about them with a google.com search.
Instead of using a rheostat or transistor to reduce a power supply voltage and create a lot of heat, PWM controls the duty-cycle of the applied power so that the average voltage is reduced. The transistors don't get very hot because they fully switch on and off.
Lamp dimmers, electric wheelchairs and even the power supply in your computer use Pulse-Width-Modulation for control and regulation efficiency.
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ofussyjoe
Apprentece
Nigeria
5 Posts |
Posted - Jan 18 2005 : 5:48:13 PM
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Thanks audioguru. I'll check that up and get in contact as soon as possible.
ofj |
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phorseps
New Member
USA
1 Posts |
Posted - Jan 23 2005 : 7:30:23 PM
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Several years ago,my brother and I built several inverters to convert 12volts dc to110voltsac.They use 2 transistors,2 resistors,and 1 transformer.Over the years,I"veused it for tv sets, electric shavers,60watt incindensent lights.
James Laird |
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12/120V inverter again
