Author Topic: my home made inverter circuit (Read 51885 times)

Nickk2057 · « **Reply #100 on:** April 05, 2013, 01:08:41 am »

and remember the video on page three on here? those are the heatsinks i am using too

c4757p · « **Reply #101 on:** April 05, 2013, 01:13:14 am »

They're big, but they're not 100W heatsinks, by a long shot. 100W is in the range of "large CPU heatsink with fan", and even then only if you're very careful about mounting.

Nickk2057 · « **Reply #102 on:** April 05, 2013, 01:16:54 am »

tho this one is at a good rating... the heatsinks and chips do not evr get hot... which is good on this setup.... and with 200W load on it it handled it beautifully

c4757p · « **Reply #103 on:** April 05, 2013, 01:21:41 am »

Remember that the heat comes from the power lost in the MOSFETs, not the power successfully transferred to the other side of the transformer. If you have a 200W load on the transformer, you're probably not losing anywhere near 200W in the FETs. You're losing I²R, where I is the current flowing through the FET and R is its R_DS(on) - a minuscule 4 milliohm in this case.

Nickk2057 · « **Reply #104 on:** April 05, 2013, 01:24:46 am »

but i tell you one thing... the load on the battery is HUGE on the input.... with no load it takes 6 amps... and with load it will take 15 to 18 amps

Nickk2057 · « **Reply #105 on:** April 05, 2013, 01:25:55 am »

but even with that load the heatsinks are still cool

c4757p · « **Reply #106 on:** April 05, 2013, 01:28:24 am »

Quote from: Nickk2057 on April 05, 2013, 01:24:46 am

the load on the battery is HUGE on the input.... with no load it takes 6 amps...

Holy shit.

Nickk2057 · « **Reply #107 on:** April 05, 2013, 01:32:43 am »

yea... i have a amp meter that came from a battery charger and it did read that.. the max amps on the meter is 15 amps

c4757p · « **Reply #108 on:** April 05, 2013, 01:39:28 am »

How hot is the transformer?

Nickk2057 · « **Reply #109 on:** April 05, 2013, 01:40:39 am »

not even hot... still cool to the touch... now when the load is hooked up it will get warm but not hot

c4757p · « **Reply #110 on:** April 05, 2013, 01:42:17 am »

With 6A flowing from a 12V battery you've got 72 watts going somewhere. I suggest you figure out where before the mystery heat sink starts to complain loudly.

Nickk2057 · « **Reply #111 on:** April 05, 2013, 01:43:42 am »

but thats with no load while the inverter is running...

c4757p · « **Reply #112 on:** April 05, 2013, 01:44:33 am »

Quote from: Nickk2057 on April 05, 2013, 01:43:42 am

but thats with no load while the inverter is running...

Yep. No load. So where is the 72W going? 72W is a lot.

It's almost definitely being dissipated in the transformer winding resistance. The transformer is not going to be pleased.

Nickk2057 · « **Reply #113 on:** April 05, 2013, 01:49:34 am »

well... the transformer is a type from a UPS unit.. which has pretty big windings in it... i will show it off when i am ready... it will be soon tho...

c4757p · « **Reply #114 on:** April 05, 2013, 01:51:45 am »

A UPS transformer might be a bit more equipped to handle that than what I suspected, but still, find the 72W. Let it run for a little while and start feeling stuff. 72W doesn't disappear into thin air, and there a lot of places it could be going. Most of those are things that are going to be pissed to have to dissipate 72W.

Nickk2057 · « **Reply #115 on:** April 05, 2013, 01:52:28 am »

btw.. here is the stuff (or numbers.. i think) on the transformer...

430-2002.11
class 130(B)
(not sure if its an "I" or an "L")eI-4 9843

its a transformer that is in a APC Back-UPS 500 unit

Nickk2057 · « **Reply #116 on:** April 05, 2013, 01:53:15 am »

ok... i will do a test with it with a 100W load on it.... and see if it will heat at those spots... but first i will try it with no load on it...

c4757p · « **Reply #117 on:** April 05, 2013, 01:54:11 am »

Are you sure it's a mains transformer and not a flyback (SMPS) transformer? They are meant for much higher frequencies.

Nickk2057 · « **Reply #118 on:** April 05, 2013, 01:55:00 am »

plus it was mostly on a Arduino chip when it was at 6 amps... maybe with this circuit it will be less... i will see tho

Nickk2057 · « **Reply #119 on:** April 05, 2013, 02:02:38 am »

ok.... with no load it uses 2 amps... and with a 100W load it uses 12 amps... which sounds about right

c4757p · « **Reply #120 on:** April 05, 2013, 02:06:03 am »

2A is acceptable for an inverter that's not even designed around its own transformer. 12A/12V in for 100W out is actually surprisingly efficient.

c4757p · « **Reply #121 on:** April 05, 2013, 02:15:22 am »

(God, this is weird. With the kind of stuff I usually do, I start worrying if it takes 100mA...)

Nickk2057 · « **Reply #122 on:** April 05, 2013, 02:22:06 am »

haha.. well i did a load test.... 100W on it for 15 minutes and it dimmed at 15 minutes around 10%

Nickk2057 · « **Reply #123 on:** April 05, 2013, 02:25:27 am »

maybe i will do a load test on a CFL next... a 22W CFL... to see how many amps it will take then on a incedesant... maybe less

c4757p · « **Reply #124 on:** April 05, 2013, 02:26:06 am »

That's pretty good. 144W -> 100W is 70% efficiency. A 60 Hz square wave shoved up the backside of a mains transformer is rarely expected to perform very well.

Edit: I now suspect your "100W" is based on the rating of an incandescent lamp, not a measurement, so disregard numbers. Still, seems like decent performance.

A CFL may not care for the waveform. Definitely try it, though, if you've got a cheap one you don't mind blowing.


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Author Topic: my home made inverter circuit (Read 51885 times)

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