Author Topic: 220v MSW power inverter only giving 117v  (Read 3629 times)

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Offline Lowku

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220v MSW power inverter only giving 117v
« on: July 14, 2015, 03:48:29 am »
Hi guys i really need help here. i have a doxin 12v to 220v 1000w MSW power inverter. It was broken and i replaced a capacitor on the input of the battery side. but now when i measure even with a true RMS multimeter it only registers about 117v. Could it be that one of the 4 transformers that are chained to give 220v might have failed? Is there a way to test it on the board? And finally can i use it when it only give 120v output instead of 220v? . The cap that was replaced was the bottom left 1 from the photos
« Last Edit: July 14, 2015, 04:05:19 am by Lowku »
 

Offline mmagin

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Re: 220v MSW power inverter only giving 117v
« Reply #1 on: July 14, 2015, 04:22:49 am »
Was that with a load on it?
 

Offline Lowku

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Re: 220v MSW power inverter only giving 117v
« Reply #2 on: July 14, 2015, 10:40:32 am »
yes, but im using a led light that works even though it is supposed to have 220v it shines on 117v, its quite strange
 

Offline dom0

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Re: 220v MSW power inverter only giving 117v
« Reply #3 on: July 14, 2015, 12:26:50 pm »
Maybe it's just set for 115 V output?
,
 

Offline Seekonk

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Re: 220v MSW power inverter only giving 117v
« Reply #4 on: July 14, 2015, 01:25:16 pm »
These are mostly H bridges. The output floats above ground.  Hence when one side is forced permanently to ground for some reason ( short or drive signal), you get 115.  Or are you just measuring it wrong?
 

Offline Lowku

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Re: 220v MSW power inverter only giving 117v
« Reply #5 on: July 14, 2015, 01:34:12 pm »
Oh is it maybe that i need to measure between earth/ground and say live? ATM i am measuring between live and neutral(COM) and i leave my earth/ground unconnected
 

Offline Lowku

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Re: 220v MSW power inverter only giving 117v
« Reply #6 on: July 14, 2015, 01:38:48 pm »
like i said its working with a 220v light, could it be that its working fine and im just not measureing correctly? As im scared to plug something  more valuable in. And how would i connect the earth?
 

Offline flynwill

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Re: 220v MSW power inverter only giving 117v
« Reply #7 on: July 14, 2015, 02:30:35 pm »
It's not at all surprising that an LED bulb is working. 

If you can find one, try testing with an ordinary incandescent bulb.  It will not be harmed by a too low voltage (and will probably give a dull red to orange glow at 1/2 voltage).

 

Offline Lowku

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Re: 220v MSW power inverter only giving 117v
« Reply #8 on: July 14, 2015, 02:48:38 pm »
Okay i will try that, but am i testing it correctly?
 

Offline mmagin

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Re: 220v MSW power inverter only giving 117v
« Reply #9 on: July 14, 2015, 04:02:24 pm »
I would definitely put a 100W incandescent bulb on it if possible.  That would give it a realistic (and mostly resistive) load for testing.
 

Offline oldway

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Re: 220v MSW power inverter only giving 117v
« Reply #10 on: July 14, 2015, 06:34:24 pm »
Measure the ac output voltage with a true rms multimeter.
 

Offline Richard Crowley

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Re: 220v MSW power inverter only giving 117v
« Reply #11 on: July 14, 2015, 06:36:14 pm »
Measure the ac output voltage with a true rms multimeter.
@Lowku said in the original post that he IS using a TRMS meter.
However, I wonder if even a TRMS meter measures a stepped "sine-wave" properly.
I would use an oscilloscope to measure the voltage.
 

Offline oldway

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Re: 220v MSW power inverter only giving 117v
« Reply #12 on: July 14, 2015, 07:37:07 pm »
That's right, sorry... :palm:
 

Offline Richard Head

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Re: 220v MSW power inverter only giving 117v
« Reply #13 on: July 17, 2015, 08:56:08 am »
Don't pull much power without connecting the power devices to a heatsink!
 

Offline oldway

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Re: 220v MSW power inverter only giving 117v
« Reply #14 on: July 18, 2015, 09:03:35 am »
Without measures and without schematics, I think it will be very difficult to make a diagnosis.
The only possibility is to do reverse engineering.

Quote
the 4 transformers that are chained to give 220v
Are they wired in serie ? What is the output voltage of each of those dc/dc converters ?

Be careful, there is high dc voltage in such a converter, don't try to repair it if you are not an electrician or an electronics engineer qualified to work with power electronics.
 

Offline Seekonk

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Re: 220v MSW power inverter only giving 117v
« Reply #15 on: July 18, 2015, 12:35:39 pm »
Massive overthinking here.  I do have an old HF inverter that put the transformers in series, about 35V each.  Always thought I could do something with that, but a use hasn't presented itself.  This is just another newbie that is measuring line to ground and imagines a problem.
 

Offline oldway

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Re: 220v MSW power inverter only giving 117v
« Reply #16 on: July 18, 2015, 01:05:52 pm »
Schematics of a 1500W 12Vdc/220Vac inverter can be downloaded here...May be, it could help. :popcorn:
http://www.eserviceinfo.com/downloadsm/64204/_.html
 

Offline Lowku

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Re: 220v MSW power inverter only giving 117v
« Reply #17 on: July 18, 2015, 05:36:21 pm »
I am measuring from line to neutral/common
 


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