Aaron's Homepage Forum
Aaron's Homepage Forum
Home | Profile | Register | Active Topics | Members | Search | FAQ
Username:
Password:
Save Password
Forgot your Password?

 All Forums
 Electronics
 Power Supply
 12/120V inverter again
 New Topic  Reply to Topic
 Printer Friendly
Previous Page | Next Page
Author Previous Topic Topic Next Topic
Page: of 63

mira
Apprentice

57 Posts

Posted - Jan 20 2008 :  10:48:57 AM  Show Profile  Reply with Quote
hello all,
i don't know whether my question fits within this topic and it is about inverters so i will ask it anyway. thanks for your reply!
i am looking for a way of boosting 100 volts dc to 250 volts dc able to supply 1 amp current.
this case resembles to the 6 volts to 12 volts inverter which is another topic, i decided to post it here nevertheless, since high voltages are involved.
thanks for your advice!
Go to Top of Page

audioguru
Nobel Prize Winner

Canada
4214 Posts

Posted - Jan 20 2008 :  11:26:31 AM  Show Profile  Reply with Quote
An oscillator can drive a pair of high voltage switching Mosfets. The Mosfets drive a custom-made 200V center-tapped to 250V transformer. The output of the transformer can be rectified and filtered into DC.
The 100VDC must supply about 2.8A (280W).
Go to Top of Page

AliKhan
New Member

1 Posts

Posted - Jan 20 2008 :  11:19:28 PM  Show Profile  Reply with Quote
Now after reading (most of) this forum... I decided to create & run this schematic in multisim.

I used 1N3600 diodes, and the simulation works.

I get a 117Vac, at around 35 watts (of course, that part doesn't quite fill the hole). But it does work.

Has there been anybody here that has reversed the polarity of the caps, substituded the diodes, and gotten this thing to work?

Go to Top of Page

audioguru
Nobel Prize Winner

Canada
4214 Posts

Posted - Jan 21 2008 :  12:01:48 AM  Show Profile  Reply with Quote
Multisim doesn't know that the transistors experience avalanche breakdown of their emitter-base junctions when a capacitor tries to drive a base to about minus 23V. Its max allowed reverse voltage is only 7V and it acts like a high current zener diode at about minus 8V where a high current flows through the backwards capacitors with the current being forced by the other transistor. Even if the capacitors have their polarity corrected then the very high current pulses would blow them up.

The transistors need diodes added to stop the emitter-base junctions from avalanching.

Calculate the base current of the transistors. It is way too low for the transistors to conduct enough current to be an inverter. The output transistors need driver transistors. Then the output would be about 120W.
Modern high current Mosfets are used in inverters today.

This inverter is a very simple square-wave one. Many electronic products don't work with a square-wave because its peak voltage is too low. A modified sine-wave should be used. It has three voltage steps where the peak voltages are almost the same as a true sine-wave.
Go to Top of Page

mira
Apprentice

57 Posts

Posted - Jan 21 2008 :  07:31:37 AM  Show Profile  Reply with Quote
thank you for your reply. your advice is very helpful.
i have another question:
i have one 24 volts battery, i have connected a 5.6 volts zener circuit and i measure 5.6 volts stable on the output of this circuit.
is it possible to connect the outputs of two such zeners circuits in series? in order to obtain 11.2 volts?
Go to Top of Page

audioguru
Nobel Prize Winner

Canada
4214 Posts

Posted - Jan 21 2008 :  12:55:56 PM  Show Profile  Reply with Quote
Of course two 5.6V zener diodes can be connected in series to make an 11.2V reference voltage.
They will be better than an 11V zener diode because the 5.6V zener diode has a stable voltage when the temperature changes. An 11V zener diode's voltage increases when it gets hot and decreases when it gets cold.
Go to Top of Page

mira
Apprentice

57 Posts

Posted - Jan 21 2008 :  11:01:28 PM  Show Profile  Reply with Quote
thanks again audioguru..
the custom made center tapped transformer you talked about, can it be done by winding twice 10 turns of 24 AWG wire on a toriod as the primary and 30 turns as a secondary?
thanks again
Go to Top of Page

audioguru
Nobel Prize Winner

Canada
4214 Posts

Posted - Jan 22 2008 :  10:09:06 AM  Show Profile  Reply with Quote
I have never made a power transformer. I just buy one when I need one.
The voltage stepup of a transformer is determined by the ratio of the turns on the secondary divided by the number of turns on the primary. If it is center-tapped then the ratio is doubled. If there are not enough turns on the primary then the current will be high without a load.
Look at the max current rating of various sizes of wire. The wire's heat is concentrated in a transformer so thicker wire will be cooler.
Go to Top of Page

mira
Apprentice

57 Posts

Posted - Jan 22 2008 :  10:11:54 AM  Show Profile  Reply with Quote
Thanks again. I will follow your advice.
Go to Top of Page

kako
New Member

4 Posts

Posted - Jan 26 2008 :  10:29:38 PM  Show Profile  Reply with Quote
Hey guys!!!

i just bought a 1500watts power inverter with 3000watts peak to try and use my air conditioner from a car battery. I dont know if i calculated wrong but my air conditioner uses less than 1200 watts and is a 120v 10amps or less. I tried using a 750 amps car battery but when i turn the air conditioner's compressor on; the power inverter turns off and starts beeping.The powert inverter haves its own power metter and when the compressor turns on it doesnt even get to 1000watts. I bought this power inverter on ebay, does this means that the power inverter isnt truly whats it says it is or am i missing something???? Is there any way for me to remove this safety switch to force the inverter to work under this conditions without shuting itself down??? i really dont care how mush time can the battery move the compressor but i really need to turn it on.

Please if you guys think of something help me out here
Go to Top of Page

audioguru
Nobel Prize Winner

Canada
4214 Posts

Posted - Jan 27 2008 :  02:59:50 AM  Show Profile  Reply with Quote
Maybe the inverter has a good specification but your car battery doesn't. 750A is "cold cranking Amps" when the battery is very overloaded which drops its voltage to 7.2V. It can supply only about 75A at 12V for maybe 3/4 of an hour. 75A at 12V is only 900W.

Your air conditioner might have a starting power surge much higher than its 1200W running power.
Go to Top of Page

kako
New Member

4 Posts

Posted - Jan 27 2008 :  6:00:32 PM  Show Profile  Reply with Quote
what type of battery you think would be best to use for this type of work???
Go to Top of Page

audioguru
Nobel Prize Winner

Canada
4214 Posts

Posted - Jan 27 2008 :  7:23:25 PM  Show Profile  Reply with Quote
I have never needed to use an inverter. I don't go camping and my electricity is very reliable.
To supply the high current to the inverter when it must supply a power surge to a starting air conditioner needs a pretty powerful battery.
Go to Top of Page

kako
New Member

4 Posts

Posted - Jan 29 2008 :  12:38:00 AM  Show Profile  Reply with Quote
I am really confused why would someone make a power inverter that goes up to 5000watts if you need the input power to be same as the output power. Is it even possible to find a battery with such Power like 1500watts that is not cranking power like car batteries???
Go to Top of Page

audioguru
Nobel Prize Winner

Canada
4214 Posts

Posted - Jan 29 2008 :  2:34:08 PM  Show Profile  Reply with Quote
A 5000W inverter gets hot. Extra input power is needed. Maybe it needs an input of 6000W from a battery.
An inverter with this much power probably uses a 48V battery to reduce its current.
There are some pretty big batteries that power electric fork-lift trucks.
Go to Top of Page
Page: of 63 Previous Topic Topic Next Topic  
Previous Page | Next Page
 New Topic  Reply to Topic
 Printer Friendly
Jump To:
Aaron's Homepage Forum © 1995-2020 AARONCAKE.NET Go To Top Of Page
This page was generated in 0.16 seconds. Snitz Forums 2000