faizanbrohi Posted June 14, 2006 Report Posted June 14, 2006 THere is an idea in my mind which i want to ask if it is applicable or not. THe Idea is to create a SInewave Oscillator , amplify the sine wave signal and that it reaches a 220V P-P , Sine wave oscillator --> Class A Amplfier --> 220V Sine wave AC Signal The only thing i don't know is how the amp need to be designed or even if this idea is correct Quote
audioguru Posted June 14, 2006 Report Posted June 14, 2006 A 220VAC sinewave is 622Vp-p.A Class-A amplifier uses its full power whether it is fully loaded or not, so becomes extremely hot and wastes as much power as it delivers at full load. It is a total waste of power at low loads.Think about using a Class-D switching amplifier that is very efficient (doesn't waste much power because it doesn't get very hot).The inverter has a very high output voltage so maybe it would be less expensive to use a high current medium voltage Class-D audio amplifier driving a stepup transformer. Quote
faizanbrohi Posted June 15, 2006 Author Report Posted June 15, 2006 i have another idea why use a power amplifier ;DGenerate a Sine wave oscillator and then use a transformer simply to step up the Signal of 10V to 220V , i mean as simple as it gets . Beacuse since the 10V is an AC SIgnal. But as simple as it is , the Current Rating of the oscillator should be very high . so we can make a sinewave oscillator using power transistors with high current ratings , or power op amps .plz reply if it is correct ??? Quote
audioguru Posted June 15, 2006 Report Posted June 15, 2006 Your idea of using a linear sine-wave generator wastes a lot of power as heat. Even if the high current output of the generator operated in Class-B to save power when the load was low, it would heat about the same power as the load at full output. Half the power from the battery would be wasted.If you use a 12V battery then the output from the generator would be a sine-wave of only about 3.5V RMS. If it was designed like an audio power amplifier then for 1000W output the circuit would heat with 1000W, the battery current would be 184A and the load on the circuit will have an impedance of only 0.012 ohms.If you use a Class-D switching output then only 5% to 20% of the battery's power would be wasted as heat. Quote
Muhammad Abu Bakar Posted June 15, 2006 Report Posted June 15, 2006 Then what about class-C amplifier?Why it isn't used at power frequencies. After all it has good efficiency! Quote
audioguru Posted June 15, 2006 Report Posted June 15, 2006 A Class-C amplifying transistor conducts only part of the time so has very high distortion. Radio circuits use them because they can tune the LC load to substatially reduce the distortion. 50Hz or 60Hz is such a low frequency that an inductor and capacitor to tune to the low frequency with high power is impractical. Quote
Muhammad Abu Bakar Posted June 16, 2006 Report Posted June 16, 2006 Soes impractical means immpossible?One more question.In an LC tank often a transfo is used as inductor(antenna on other side). Does this transfo has some rigid inductance or it depends upon the load impedence? Quote
audioguru Posted June 16, 2006 Report Posted June 16, 2006 Look in Google for "ferro-resonant transformer". It has a third winding that is tuned by a capacitor to be a tank circuit. It is designed so that its core saturates which makes voltage regulation but a square-wave, then the tuned winding converts the square-wave to a sine-wave. Quote
faizanbrohi Posted June 18, 2006 Author Report Posted June 18, 2006 I think you don't get the point i am saying if use a ordinary sine wave oscillator and then attach it to a Step up trasformer , that is it Quote
faizanbrohi Posted June 18, 2006 Author Report Posted June 18, 2006 ok i get it , it heats more at the oscillator stage , but it can be a way to tackle it good .... Quote
audioguru Posted June 18, 2006 Report Posted June 18, 2006 ok i get it , it heats more at the oscillator stage , but it can be a way to tackle it good .... It is not good to make an inverter that wastes as much power as the load uses.An inverter should be efficient, and use a switching amplifier instead of a linear amplifier. Quote
faizanbrohi Posted June 18, 2006 Author Report Posted June 18, 2006 So are there any ideas for a switching amplifer and how is it to be interfaced with my oscillator idea... and the transformer one.. Quote
audioguru Posted June 18, 2006 Report Posted June 18, 2006 So are there any ideas for a switching amplifer and how is it to be interfaced with my oscillator idea... and the transformer one..Class-D switching amplifiers are complicated. Ones for audio use a fairly low supply voltage. TI has an IC with up to only 240W output.A sine-wave oscillator would drive a class-D amplifier which would drive a stepup transformer. Quote
faizanbrohi Posted June 18, 2006 Author Report Posted June 18, 2006 A switching Class D AMplfier is hard to make , is it no other idea to use any other type of amplfier. Quote
audioguru Posted June 19, 2006 Report Posted June 19, 2006 Maybe your load doesn't need a sine-wave and will work from a simple square-wave inverter.A "modified sine-wave" inverter has a square-wave with a step in it and isn't too hard to make. Quote
kachew Posted July 25, 2006 Report Posted July 25, 2006 Dear Audioguru, Do you have the modified sinewave inverter circuit ??? can share it out for our knowledge?? ;D ;D just asking.... Quote
audioguru Posted July 25, 2006 Report Posted July 25, 2006 Do you have the modified sinewave inverter circuit ???Somebody posted a circuit but it is on the broken hard drive of my old computer. Quote
kachew Posted July 25, 2006 Report Posted July 25, 2006 dear audioguru,can u describe how its look like?? hehe ;D ;D maybe i have it... ;D ;D Quote
audioguru Posted August 9, 2006 Report Posted August 9, 2006 A square-wave inverter 's output goes: positive pulse, negative pulse, positive pulse again, negative pulse again and repeats.A simple modified sine-wave inverter's output goes: positive pulse, 0V pause, negative pulse, 0V pause, positive pulse again, 0V pause again, negative pulse again, 0V pause again and repeats.It is not difficult to make the 0V pauses.I don't bother with a modified sine-wave inverter because tools with variable speed motors and other things don't work properly with it. Quote
kachew Posted August 16, 2006 Report Posted August 16, 2006 dear audio guru do u have any idea to implement this?? for example we take kasamiko inverter how do we make it from square wave to modified sine wave?? ??? ???thanks lots Quote
audioguru Posted August 16, 2006 Report Posted August 16, 2006 You could make a modified sine-wave with a CD4047 oscillator and a CD4001 quad NOR gate or CD4011 quad NAND gate.The oscillator of the CD4047 and its Q output would be gated and drive one of the push-pull output transistors. The oscillator output and the Q-Not output would be gated and drive the other push-pull output transistor. Quote
kachew Posted August 16, 2006 Report Posted August 16, 2006 dear audioguru can u show or tell me how can i connect it to be modified sine wave?? can i use the circuit i posted here http://www.electronics-lab.com/forum/index.php?topic=1360.112 to change from sine wave to modified sine wave inverter? cos i wan to use mosfet than transistor to increase the efficiency of the inverter...thanks lots ;D ;D Quote
audioguru Posted August 16, 2006 Report Posted August 16, 2006 I already told you how to connect a CD4047 with logic gates that drive your Mosfets with a modified sine-wave. The timing diagram looks like this:EDIT: Corrected the clock's pin number. Quote
kachew Posted August 17, 2006 Report Posted August 17, 2006 hi audioguru,i just wan to know the use which pin to connect to the pin Q and inverted Q of cd 4047? :'( :'(and how about i add LM358 amplifier to increase the output current from the CD4047 in order to increase the efficiency? ??? ??? Quote
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