If you will go back to the post made by Toprudder in the
3,000 Chinese Generator Info thread on 7/11/10 at 5:07 p.m., you will find the discussion, information, test results and conclusions that were the result of a power analyzer test of a WIFO converter/charger. The post has been reproduced in the boxes below my current comments:
Note the "back EMF" currents that can develop with the WFCO converter, which is perhaps the most commonly used converter as OEM equipment by the RV industry (it is less expensive).
The related postings where I made scope measurements of the output from a synchronous generator connected to the WFCO converter appear several postings before Bob's test results. It may be valuable to go back and look at those as well to see what I mean about the WFCO "being generator unfriendly."
The WFCO is NOT a generator friendly converter. It is especially unfriendly to a digital generator. It will apply loads at the junction of the switching transistors in a digital circuit that are greater than what you will measure with a conventional amp-meter or those that may be detected by a circuit breaker or the voltage drop across a resistor that senses digital overload.
Bob did not get to test the Progressive Dynamics converter. I did run some test with the PD where I measured waveforms with a scope as I did with the WFCO. Those tests showed that the PD converters DID NOT cause distortion and loading on the output waveform any more than another appliance. Therefore, my conclusion is the PD is much more generator friendly and less likely to cause damage to a digital from the back EMF apparent at the converter input.
toprudder wrote:
professor95 wrote:
toprudder wrote:
I will be pulling my camper next weekend and will be pulling it by where I work, so I may hook it up to a power analyzer to take a look at it. You've got my curiosity up. :)
.... and mine too. I hope you are able to run the test and will share your findings. The only power analyzer I have is a 60 watt incandescent light bulb or two wet fingers.
OK, was able to stop by work on the way back from a trip, and hooked up the camper to a power analyzer. I turned off all breakers except for the converter. Since I had run the generator most of the morning, and then had the camper connected to the tow vehicle on the way back, the camper battery (a single G24) should have been fully charged. In order to load the converter more, I turned on all the lights in the camper.
The power analyzer system includes a solid state power source. Think of a powerful sine-wave inverter, but this one is powered by 208v three phase. There is also instrumentation to measure voltage and current waveforms and harmonics. We use this system to test products for compliance to (mostly) European requirements.
Here are the voltage/current waveforms:
As I suspected earlier, the current waveform is terrible. Current only flows when the voltage is near the peak. Also notice the amount of peak current, over 20 amps!
Here is the harmonic summary:
The European limits were used, but tested at 120v (European power is 230v, between phase and neutral). The WFCO converter failed the limits miserably.
The software for the analyzer also checks the voltage waveform to make sure it meets the requirements for the test standard. In this case, it failed. This is the first time I have ever tested anything that the voltage waveform requirement failed. I can only guess that the current waveform from the converter was so bad that it was distorting the voltage waveform from the power source.
Professor, given the output impedance of a generator, I'm not surprised you saw the chopped-off waveform that you did.
Now I wish I had a different brand (Iota or Progressive Dynamics) to test.
