Question about inverters
Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=54388
Printed Date: April 29, 2024 at 5:52 AM
Topic: Question about inverters
Posted By: Poormanq45
Subject: Question about inverters
Date Posted: April 21, 2005 at 10:12 PM
If a power inverter draws 20amps from a 12v source and converts it to AC 120v:
What would the theoretical maximum wattage/amperage at 120volts be?
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Replies:
Posted By: Poormanq45
Date Posted: April 21, 2005 at 10:15 PM
Please feel free to describe it as technically as you want
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Posted By: Poormanq45
Date Posted: April 22, 2005 at 1:29 AM
anyone?
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Posted By: haemphyst
Date Posted: April 22, 2005 at 8:31 AM
12v X 20A = 240 watts IN
240w / 120v = 2A OUT
There is your theoretical maximum RMS current. I say RMS current, because 120v is the RMS voltage, 170 is your p-p voltage, so your absolute current will be slightly lower.
Also, this assumes a 100% efficient device, which does not exist. Most of your modified sine wave inverters (the most common output waveform for all of the inexpensive inverters today) will ron about 90%, so your real-world current capacity will be on the order of 1.75 to 1.8 amps.
It's all still 240 watts, you get no free watts (power).
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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
Posted By: stevdart
Date Posted: April 22, 2005 at 10:35 AM
haemphyst wrote:
It's all still 240 watts
Wouldn't it be 240 watts less the loss in conversion efficiency...or 240 X ~90% = ~216 watts?
Posted By: haemphyst
Date Posted: April 22, 2005 at 12:23 PM
Yes. What I MEANT was, 240 watts in must equal 240 watts out, INCLUDING the heat lost in conversion, in this case, about 24 watts will be blown off as useless heat. You are corrcet, the USEABLE power would be around 214 watts, given a 90 percent efficiency.
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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
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