Inverter problem

[Tom in NH]

I'm using an xantrex xpower plus 2500watt simulated sine inverter. It works well for most everything. I'm having trouble running my microwave on it though. The ac voltage stays high enough (122 volts dropping down to 120 volts in a couple minutes). Typically what happens is I set the microwave for 2 minutes, run it, and then check my cup of water and it's still cool. I try to run it for another cycle and the microwave gets angry at me. It gives me an F7 error report--"computer board failure." When I reconnect the microwave to grid power, everything works normally.

I'm guessing there is something about the waveform that the microwave does not like.

Does anyone have any suggestions for modifying the waveform or the powersupply of the microwave? Or am I all wrong and the problem is somewhere else? What might I try to diagnose the problem? Thanks in advance for your ideas.

[Paulm]

You might have to get a sine wave inverter. Those cheaper modified sine wave inverters don't run everything without glitches.

[John II]

We have run the old fashioned Trace 1512 for years (it's a modified wave inverter ) and it runs our microwave just fine. It may be that some microwaves are more tolerant than other's.

John II

[Vernon]

Power supplies for electronic devices operate by rectifying the incoming AC and charging a capacitor to peak. The energy in this capacitor then operates the switching supply. If the peak of the incoming AC is clipped this critical raw voltage will be low and the power supply, depending on its tolerance for this condition, may not operate properly.

The magnetron may depend on a sinusoidal waveform, shaped by a network in the high voltage circuit, to kick it into oscillation. A magnetron is a vaccum diode with a magnet that causes the electron beam to curve past resonant cavities in the anode, these cavities oscillate and bunch the electrons and that amplifies the oscillation. Too high a voltage caused by a square wave would cause electrons to hit the anode early, too low and they may pass to far from the first cavity.

[deerslayer660]

    i have seen this befor the way i fixed it was to get a microwave that uses a dile timer that worked for me no touch pads or ckt board and food still gets hot

[FishbonzWV]

Don't know what kind of power hog this puppy is but I'm going to install it between the generator and the inverter/charger. Our gen kinda fluctates output depending on the temp of gen. After about 20 min of run time the voltage drops.

This is a Sola power conditioner 1000w. (Free to me)

Don't know what they cost but you might look around for one.

I've seen some large ones on the military surplus web site.

http://www.govliquidation.com/index.html

[jimjjnn]

Paul is correct. The microprocessor chip in microwave has to have clean power. If you can find one of the types with the wind-up timer instead , it should solve your problem.

[Nando]

The SOLA transformer is about 75 to 80 % efficient, also it requires accurate input frequency because it is a tuned ( resonant) transformer that saturates the core every half Hertz,

I do not recommend it the frequency is more than 1.5 hertz away from the 60 HZ.

I designed them years ago and I don't think that I ever tried or tested them with a Modifed Sine wave, it may work since the core is saturated ( even better).

Regards

Nando

[laskey]

The problem with using a saturation transformer here is that it turns even good AC into a modified sinewave shape.  That's the nature of a saturation transformer, it clips off any voltage exceeding it's saturation voltage.  It won't solve your problems with modified sinewaves going into it, nor will it hurt it, or be hurt by it.  The only power conditioners that will help the problem are "always-on" UPS's that produce true sinewaves (kinda rare and expensive).  You're still better off buying a true sine inverter just for the stuff you have that requires a true sine.

Cya,

Chris