| T O P I C R E V I E W |
| adeel_usmani |
Posted - Aug 13 2008 : 3:51:39 PM
hell, audioguru
i am really confused i saw a msw ups which was rated 220 volts and used 12 volts battery when i checked out put volts of ups it was only 160 volts but my fan and all appliances are working good like work on 220 volts ac . then i checked the transformer of ups and my surprise increased when i saw there was 8-0-8 volts transformer how this transformer is working on 12 volts battery .
i really need ur help . i want to make a ups of msw i have transformer of 12-0-12 /220/300 volts which i got from a square wave ups which was giving 300 volts output but my fans and bulb are not damaged. if i used that transformer and used ur msw circuit then will this transformer work and which primary winding i should use is it 220 volts or 300 volts.
i really want to know how 8-0-8 volts transformer is used 12 volts and
how to convert dc to ac volts i mean if i convert dc to ac (msw) will 12 volts increases or decreases. |
| 3 L A T E S T R E P L I E S (Newest First) |
| audioguru |
Posted - Aug 14 2008 : 7:19:03 PM
An old IRFP150 has a max output current of about 30A. A pair of them makes a 250W MSW inverter.
The stepped output waveform of a MSW inverter works with most products.
The 12V-0-12V/345V transformer will prodice an output of about 203V RMS at 250W which is too low.
If better Mosfets are used then the output will be about 234V RMS at 250W or more.
The transformer must be good.
A 12V-0-12V/345V transformer is the same as a 8V-0-8V/230V transformer. |
| adeel_usmani |
Posted - Aug 14 2008 : 3:41:52 PM
very thankfull to u . this information is very help full for me . can u please tell me if i used a transformer having correct ratio i mean if i used 12-0-12/345 transformer and i feed MSW to transformer through fet like irfp150 . so the out put voltage will be suitable for my pc and other electrical appliances . and if i wrongly give this transfomer square wave will all electrical applicance burn. and what about effeciency am i decreasing effeciency of transformer?if i used that kind of transform that i mentioned as msw used 8-0-8/220 or some 7.5-0-7.5/220 transformer. |
| audioguru |
Posted - Aug 13 2008 : 5:23:20 PM
The peak voltage of a MSW inverter is 1.414 times higher than the peak voltage of a square-wave inverter. So a transformer needs to have 0.707 times less rated input winding voltage. 8V is 0.67 times which is close enough. The ratio of 8V to 230V is 28.75 times. The ratio os 12V to 300V is 25 which is a little low. Then if the circuit uses Mosfets to drive 12V into the transformer, the 300V output will have a peak voltage of 300V and the RMS voltage will be 212VAC.
The MSW inverter produces a waveform that an ordinary cheap voltmeter cannot measure accurately. a voltmeter with a "True RMS" feature is needed to measure it. |
