Generator Hz Issues

Re: Generator Hz Issues

"Line Conditioners"--Another can of worms. There are many different types of line conditioners--So you have to make sure that you understand the terms and usage of any particular type unit.

A couple types... There are those that are multi-tap Auto Wound transformers--These are basically variable transformers with a controller that can take (for example) 180-264 volts and control the transformer to give you ~240 VAC stable electricity voltage.

Another is a "ferroresonant transformer".

The ferroresonant transformer, ferroresonant regulator or constant-voltage transformer is a type of saturating transformer used as a voltage regulator. These transformers use a tank circuit composed of a high-voltage resonant winding and a capacitor to produce a nearly constant average output voltage with a varying input current or varying load. The circuit has a primary on one side of a magnet shunt and the tuned circuit coil and secondary on the other side. The regulation is due to magnetic saturation in the section around the secondary.
The ferroresonant approach is attractive due to its lack of active components, relying on the square loop saturation characteristics of the tank circuit to absorb variations in average input voltage. Saturating transformers provide a simple rugged method to stabilize an AC power supply.
Older designs of ferroresonant transformers had an output with high harmonic content, leading to a distorted output waveform. Modern devices are used to construct a perfect sine wave. The ferroresonant action is a flux limiter rather than a voltage regulator, but with a fixed supply frequency it can maintain an almost constant average output voltage even as the input voltage varies widely.
The ferroresonant transformers, which are also known as Constant Voltage Transformers (CVTs) or ferros, are also good surge suppressors, as they provide high isolation and inherent short-circuit protection.
A ferroresonant transformer can operate with an input voltage range ±40% or more of the nominal voltage.
Output power factor remains in the range of 0.96 or higher from half to full load.
Because it regenerates an output voltage waveform, output distortion, which is typically less than 4%, is independent of any input voltage distortion, including notching.
Efficiency at full load is typically in the range of 89% to 93%. However, at low loads, efficiency can drop below 60%. The current-limiting capability also becomes a handicap when a CVT is used in an application with moderate to high inrush current like motors, transformers or magnets. In this case, the CVT has to be sized to accommodate the peak current, thus forcing it to run at low loads and poor efficiency.
Minimum maintenance is required, as transformers and capacitors can be very reliable. Some units have included redundant capacitors to allow several capacitors to fail between inspections without any noticeable effect on the device's performance.

These type of transformers are very sensitive to line frequency and would not be a good choice for use on a generator with poor frequency regulation (plus, true F.R. transformers are probably obsolete now--expensive, not very efficient, heavy/large/expensive, etc.).

In general, a "simple" battery charger should not be very affected by frequency variation, and as long as the input voltage is within acceptable limits--I would not even bother with a line conditioner.

If you can find a Power Factor Corrected AC Battery Charger--That would even be better. A typical PFC input power supply designed for the "international" market (battery charger, computer power supply, etc.) can take from ~95 volts to 264 volts at 50-400 Hz -- A very wide input power input and do it efficiently and cost effectively.

The Xantrex TC2 12 volt battery chargers (and 24 volt) appear to be a very nice AC battery charger for use on small gensets (and on normal grid power).

Auto-ranging universal input voltage (90-265 Vac, 47-63 Hz) is also compatible with a generator or other low-quality power sources

Note, this is not "Auto-Ranging" (I don't think) where the power supply runs from 90-135 and 180-265 volts and running at 150 VAC would cause problems--This is a true "wide range" input (anything between 90-265 VAC is fine).

Xantrex in years past has been having some sort of issues with getting these battery chargers out to their retail stores (and changes in product line due to Schneider takeover). I have no idea what is available today or where to get them (other than Google/calling Xantrex).

Is this your generator?

http://www.allpoweramerica.com/?_escaped_fragment_=apg3014/c1lco#!apg3014/c1lco

I guess I am a bit confuses--Where is the 220 VAC power coming from/used? Is that from your 120/240 VAC inverter or are you using a 230 VAC genset (50 or 60 Hz)?

My concern is the AC Generator output power quality... I don't think you are getting 109 VAC and 90 Hz... The "typical" AC Battery charger is a very simple device. And has very poor power factor:

Here is a beautiful picture showing the relationship between voltage and current for a rectifier/capacitor front end (from here):

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When the battery charger pulls power just during the current peaks, that can cause the AC generator output voltage to sag during these peaks--And "double" the number of peaks seen by a frequency counter (or other miss-counting events, depending on how the counter actually works). Notice the slight "shoulder" in the wave form in this picture when the current spike starts.

Try measuring the frequency (and votlage) from the generator with a "resistive load" (100 watt light bulb, electric heater, etc.). "Non-Linear" loads can really distort the AC output voltage of under sized (or "cheap") generators.

Here is an example measure by somebody with a "cheap" generator running "unloaded":

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Without a scope--It is difficult to figure out what is happening.

-Bill

Re: Generator Hz Issues

An isolation transformer has its own issues... To get a good image of the true voltage, the transformer would probably have to have a pass band of 10kHz to 50kHz (to show all of the visible distortion of the AC Wave form).

I am not sure--But a typical AC isolation transformer probably does not have that sort of band width.

So, you would need to look at an audio isolation transformer, and get one with 600 VAC or higher isolation rating. May not be that easy to find at the local radio shack.

Just to be very clear--There are two ways of using "isolation transformers"... First would be to get a 120 to 120 VAC transformer and put the probe on the isolated output (or get a 120v:12v transformer--probably even safer). I am not sure how good the fidelity will be, but it is probably "good enough" to see the basics of what is happening.

A second is to use a 120v:120v isolation transformer on the AC input to the scope (and not connect the green wire). That can work but be dangerous as the "grounding clip" to the power line can make the chassis of the scope "hot".

And a third way--There are (or at least were in my day) battery powered scopes that were OK to directly measure AC mains with (using the correct probes).

All things being equal--I would get a cheap 120:12 or 120:24 volt (or similar) isolated step down transformer (or old door bell transformer, etc.) and connect the scope to the output of the transformer and measure the signals.

-Bill

Re: Generator Hz Issues

I don't have an scope images of really bad generator waveforms... They can look almost like two 60 Hz wave form offset by a 1/4 cycle. And there are other ways of messing up a wave form:

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This is from an electronic florescent ballast "flat topping" the voltage wave form... But also notice the "ringing"--Something too that can confuse a frequency meter.

All this is just guess work--Until you can do some further debugging (scope picture, or try a resistive load to "stabilize" the generator output--100 watt filament lamps where used very commonly--try to buy one of those now)--I am not sure I am being very helpful in "fixing" your difficulties.

Sorry,
-Bill

PS for Chris: These are just Googled examples of "poor alternator output" voltage wave forms that are examples of why a simple frequency counter can be miss-lead by non-sinewave voltages. I have no idea what the output of this particular genset may be.