Magnum 4000 w 110/220v inverter prodlem

Hooked up my inverter and getting 164v per leg ... not sure why. Any help would be appreciated.


  • mcgivormcgivor Solar Expert Posts: 3,817 ✭✭✭✭✭✭
    edited March 2019 #2

    The root mean square, RMS of 164V is 115.9V, what is used to measure the voltage?

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  • inverterproblemsinverterproblems Registered Users Posts: 3

    I used a small voltage meter..all lights are running good but fridge is doing something funny... it is possible the fridge has some problems

  • inverterproblemsinverterproblems Registered Users Posts: 3

    I will take a better look at the the fridge

  • BB.BB. Super Moderators, Administrators Posts: 31,688 admin

    No matter what, your voltages do not sound correct... But what is your AC mains voltage? 120 or 240 VAC of your inverter.

    There is an issue with volt meters... The modern "simple/cheap" digital meter just measures the peak voltage and divides by the square root of 2 (1.414). This is the conversion from peak sine wave AC signal to RMS (Root Mean Square) which is the "average" value of the AC waveform (i.e., a DC voltage of 120 VAC is equal to a peak 170 volts AC sine wave in the equation of Power=Voltage*Current).

    When working with Square Wave and Modified Square Wave inverters, the peak voltage measured by a "cheap" Digital Multi-Meter" then divided by 1.414 is "wrong" and will give you a lower AC voltage reading (something like ~100 VAC). You need an RMS Reading voltmeter to properly measure the "effective" AC voltage.

    Note that some equipment may not work as well on MSW (Modified Square/Sine Wave inverters) because of the MSW wave form. Transformers, induction motors, and refrigerator compressors can get hot (and have early life failure). Some "computer" type power supplies can fail. It is the old 80% of stuff will work OK, and 20% may not... And it can be hard to figure out which is which.


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  • TecnodaveTecnodave Registered Users Posts: 418 ✭✭✭✭

    Pretty sure that that inverter is sine wave....AFAIK Magnum Energy does not sell a modified sine wave inverter that is 120/240 volts 4,000 watts. The only ones that I am aware of is the MS-4024PAE, MS-4048PAE, MS-4024AE and MS-4048AE. All of those units are true sine wave.

    I have a MS-4024AE and my voltages are norm 120/240 with voltage sagging on heavy loading and is somewhat slow to recover.

    I would look at the voltages with a better voltmeter. I use mostly Fluke both averaging and true RMS as well as wavetech and other high quality meters and find the readings within the norm.

    when testing unknown modified sine wave inverters my old Fluke ET-21 (industrial version of 77) does not read correctly but about 20% low, it does have a current NIST certificate. So time for the true RMS meters. your exact model of inverter and what kind of meter you are using. That will help all who would diagonis of your situation.

    And do check your battery in your meter, My Fluke will read high by 80-130 percent on the 9 volt battery being below about 7 volts.


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