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doron

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Everything posted by doron

  1. thanks audioguru for that piece of info. So are you saying that the 4 paralled transistors though each has a power dissipation of 115W alone when the are put together we get only 50W dissipated,how come?
  2. I fixed the problem on the oscillator so evrything is working ok now. I mounted the 4 2N3055 on one heatsink for each cycle,say when we have 1 cycle so i was curious as to how much heat they are going to dissipate.you last said you need the specs for the heatsink so i was wondering what you were talking about What exactly are you talking about when you say "Heat Specs" and can you give an example in relation to the 4 mounted transistors knowing their characteristics?
  3. i am having problems with my square wave generator.What is happening is that at the pins 10 and 11 of the CD4047 there is a constant voltage(I am using 5 Volts d.c to prevent heating of the chip) instead of the original square wave that i was getting initially when i connected the circuit.Then it was oscillating between 5v and 0v. I have changed the chip 4 times and still there is no change so now i don't know what to do.I tested all the chips and they were fine,together with the LM358 Op Amp and everything is ok but NO SQUARE WAVE!!!! >:(
  4. hie i was wondering if you could use 3A power diodes in place of the 2A for back emf protection? Does the 100R,1/4W resistor on the schematic mean 100 Ohms or you can use any value of R as long as the ratio between the 100R,1/4W and 0.1R,10W is maintained? Can i use a 60A Circuit breaker in place of the 50A power switch or relay
  5. On the schematic given for the 500W inverter,ther are values given as 100R,1/4W is this suppossed to be 100 Ohms,1/4W or I can use any value for R as long as it has 1/4w dissipated? The darlington paired transistors;are they to be used for amplifyng the signal out of the CD4047 chip or for some other purpose? If you can't mount the emitter resistors on the heatsink,where are you going to place them?I saw the pictures by COOPERMAN and he had mounted them on the side of the heatsink(see his pictures attached) You said that the 3 paralled 0.47 Ohms,5W will have the project's voltage output reduced,by how much will the output voltage be reduced and what are the effects on the load connected? ;)
  6. What type of loads/appliances/devices can be used with this inverter because i believe we can't use it on critical loads like a computer or some other data capturing devices? What is the purpose of the 0.1Ohm,10Watt resistor?Why can't we use a wire for short circuiting if that is what we want to achieve when the current is being drawn by the load as 0.1 Ohm is really no resistance at all? What is the purpose of the 4 2N3055NPN Transistors bacause I thought they were for current sharing because the 50Amps is too much for one transistor,eg, 50/4=12.5Amps.The transistors max rating is 15Amps so i thought they could handle this much current? What type of power MOSFETS can i use in place of the transistors? How do you connect the collector of the 2N3055NPN transistors when you have mounted them on the base of the heat sink? How do you place the resistors onto the heatsink? I've found some 0.47 Ohms,5Watt resistors and I wanted to parallel them in 3s so i get an effective resistance of (0.47*0.47)/(2*0.47)=0.235 (0.235*0.47)/(0.235+0.47)=0.157 Ohms dissipating about 15Watts Do you think this will work in place of the 0.1 Ohm,10Watt resistors?
  7. just how much load would the circuit be able to withstand if i use my 0.24 Ohms which dissipates about 3Watts on the emitter side of the resistors because they are the only ones that i can find close enough to the 0.1 Ohms,10W resistors? I am asking this because i don't necessarily have to produce 500W as yet,i just want to test the circuit with the resources that i have.
  8. audioguru if i use my circuit on a device that requires about 400w of power using the 0.24,3W emitter resistors,they should work shouldn't they?I'm asking this because the last time i spoke to you,you said they would blow
  9. just how much power can you handle if you use 0.24 Ohms.3W on the emitter resistance and how do you find that out(mathematically i mean)? How is one heatsink different from the other?I thought they were all the same.
  10. Audioguru,i think using resistors is a wise idea coz i'm positive the transistors will blow but i have decided to use the 0.2 Ohms,3W in place of the 0.1 Ohm,10W so does that have any effect on the circuit?Hope not. I got the transformer so lets wait and see what happens when i connect the circuit.Can you fit 4 power transistors on the heatsink used by Cooperman coz i have 2 Heat sinks that are similar to the one used by him.I thought we needed 4 power Transistors for the circuit to work but i'm only seeing 3 on Cooperman's circuit,does that do the same work?
  11. audioguru,Cooperman how are you?The reason why i thought of using the 4.7Ohms was because i could not find any 0.1 Ohms,10W resistors in my town(Harare,Zimbabwe) so had not put into consideration that voltage drop across the resistors.However I thought that the current from the pre driver transistors would compensate for the losses incurred. My question is can i not use any other value of resistance besides the 0.1 Ohms,10W resistance and the 100 Ohms,1/4 W to get the same power output of 500W using the same components i.e the 2N3055 & 2SC1061 TRANSISTORS? I do know that when fully switched on(the 0.1 Ohm,10W) that is when i can get the 500w assuming that i do have a 500W load connected to the output of th transformer. Do you have any idea where i can get the 12v-0-12v to 220v transformer from any old household appliance coz i can't seem to get it from anywhere? Thanks in advance you guys and Cooperman would it not be easier if you mounted the 2N3055 transistors the other way coz then it would be easier for you to then connect the resistors to the emitter of each transistor?
  12. hey you guys how are you doing?It's been long hasn't it?Anyway i'm back and i got more questions than answers. First,does the ratio of the 0.1R,1/4W Resistor to the 0.1R,10W Resistor have any effect on the power output because i managed to get 4.7Ohms,10W and 4.7k,1/4W so i don't know if i can still get the desired output.I did my calculations and got about 122W!!This comes from ( V/R)=12/4.7 =2.553Amps This value is then multiplied by 4 for the 4 transistors to get 2,553*4=10.212Amps Now the Power available is then P=V*I = 12*10.212 =122.553Watts Secondly,the output on the Transformer has a frequency of 50Hz Square Wave.Does this work on ordinary household appliances because i was thinking of adding a sine wave filter at the output of the transformer?Do you think it will work and do you have any idea if i can build one? You guys are the best,so i hope you can really help me out on this one coz i could really use yor profound knowledge Later Doron
  13. audioguru thanks,what you said is what i had in mind but i wasn't sure about the calculations of the gains,for example,the LM358 OP AMP. The 2SC1061 has a minimum gain of 35, the 2N3055 has a gain of 20 so aren't you supposed to use that in your calculations? You know what?Maybe it would be better if you could show me how you got the output current form the chip(assuming that the input current to the chip is about 10mA) to 15mA to 1A then to 12A and finally to 50A. My assumption is that you would be using the transistor's current gain but its not adding up. Hey,initially how much current would be flowing when you switch on the inverter?I thought it was around 42Amps. Once again thanks for the invaluable wisdom you dished out,you really helped me understand the circuit better. Looking forward to hearing from you soon Doron
  14. hie, i just joined the community and i was hoping that somebody,anyone pliz help by explaining the modified inverter that Ronnie.B.Tabanao showed.I could really use some help coz i can't understand it. I
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