Does Your Inverter "Track"?

Geez 70-years old and I'm like a 9-year old. Endless curiosity. The reason I ask is an Inverter - Battery - charger makes a wonderful truly isolated source of AC power. Not an inverter/charger but a separate charger maintaining the battery while (for me anyway) a Samlex PSW 300 watt inverter delivers ultra clean AC. The Samlex seems to track .4 volts per tenth vdc on the primary. Something else really wierd I noticed last night. Megawatt output voltage is much stabler with the ten turn pot installed. I hope I am dreaming this...

MEXICOWANDERER wrote:
Maybe I need to define this better than I did :)

1,000 watt inverter

200 watt tungsten load

RMS @ 12.00 vdc
RMS @ 14.00 vdc

PSW inverter:

RMS @ 12.00 vdc = spec'd AC output voltage
RMS @ 14.00 vdc = spec'd AC output voltage, waveform the same as 12 volt input

MSW inverter:

RMS @ 12.00 vdc = spec'd AC output voltage
RMS @ 14.00 vdc = spec'd AC output voltage, waveform different from 12 volt input

I'm not meaning to say that the output regulation is perfect. It should, however, be "pretty good".

Hi Mex,

What I've noticed is that as the load increases the DC input voltage sags. Over time that continues but AC output voltage is not 1:1 with the DC sag. Amps of consumption go up as DC input voltage sags as does AC output voltage but the inverter does try its best to support the AC voltage. Truly large loads do cause AC voltage drop, just as they would on shore power.

The same thing happens with a Yamaha 3000 sIEB inverter generator, but AC voltage (of 122 unloaded) is more "resistant" to sag than shore power. If I push the Yamaha to the edge, AC voltage does start to sag.

I know the Honda generators operate with an AC output of 127 volts.

MEXICOWANDERER wrote:
From day whatever low voltage limit may be

As battery voltage increases output AC voltage similarly increases?

This has my curiosity and I am going to have to test, but my Magnum 3000 list +-3% 120v between 8.5 and 16.5 volts in the manual.

My inverter never really runs at 14 volts. More like 11.0 to 12.5

Will check tonight with fully charged batteries and again in the morning

That test I can perform, using a 200 watt electric heater I keep under my desk
I can even use my oem 15 amp K-A-W to check voltage

My first response was based on using my big 1100 cooking watt MW

Maybe I need to define this better than I did :)

1,000 watt inverter

200 watt tungsten load

RMS @ 12.00 vdc
RMS @ 14.00 vdc

I do not know the answer and I am curious to know if true sine wave circuits
Automatically eliminate tracking and for pseudo sine wave if low frequency is less prone to tracking than high frequency units.

All of the modern inverters I know of regulate the RMS output to be relatively constant over their spec'd range of DC voltage input. The high voltage input to the actual inverter circuitry is proportional to the DC input voltage (i.e. not regulated). The inverter regulates the AC output voltage using PWM. In a PSW inverter, the pulses are behind a filter which smooths them into a sine wave. So the changes in the pulses, due to DC input variations, are not seen in the AC output. MSW inverters use the same technique, but with only 2 pulses per AC cycle and no filter, the output waveform changes with the DC input voltage while retaining a constant RMS value. With a high DC input voltage, the output pulses are shorter width at a higher voltage. As the DC input voltage goes down, the output pulses trend to a lower voltage and greater width as the RMS value remains constant. Some loads "don't care" about the changing waveform, others do. Most microwave ovens and some DC power supplies are highly dependent on the peak voltage and their performance will change when driven by a MSW inverter as the DC input voltage changes.

How to test for that? Easy if you mean unloaded AC voltage at the inverter receptacle.

With an inverter loaded, more load, battery input voltage sags more. Don't know what happens to output voltage. With less load for a test comparison, you would have a higher battery voltage but maybe also less of a loaded AC voltage?

Would that even be a valid test, or is it only valid with the inverter unloaded but on a low and full battery comparison?