an unusual charging problem

[pianotuna]

Hi all,

I'm generator charging from need for the first time in my life. It is not hot enough to run the roof air.

Here is a bit about the system.

Magnum 3000 Hybrid 12 volt to 120 volt with ARC remote

Yamaha 3000 sIEB inverter generator

4 139 amp-hour surplus acid telecom 12 volt batteries totaling 556 amp-hours. These are a bit unusual as their specific gravity is 1.3 rather than the more normal 1.275. They have a slightly higher voltage.

256 watts of solar into a Blue Sky 3024 di controller.

voltage monitored with a kill-a-wall unit

Wattage monitored by an Efergy Elite classic watt meter.

Charging rate monitored by the Magnum remote.


Conditions:

Batteries were not fully charged yesterday and were used overnight. Remote display said 12.5 volts.

I started the generator leaving it at maximum output.


I made the following observations:

Remote went immediately to float charging at 10 amps

Load was the fridge at 311 watts (2.5 amps)

Voltage was 122.

I turned off the fridge. No change in charging rate or voltage

I increased the load on the system by turning on the water heater 1300 watts (11 amps) voltage 118

Charging rate increased to 39 amps.

I turned off the water heater and charging amps slowly dropped back down to 10.

The "trigger" point for higher amp charging appears to be about 1300 watts. Doing so may double the fuel consumption rate. I'd prefer to avoid this.

[MrWizard]

Mike long time since school
50 years
Thanks for the refresher

[CA_Traveler]

Yup, basic AC circuits 101. Thanks Mike.

[MEXICOWANDERER]

Damned aching root canal remnants...laughing damned near killed me.

My question is this...on the DC high voltage line through Ely Nevada, the inverter techs (much more advanced that I), kept a continuing uproar going about the inverter lapsing into what can be described as a sawtooth waveform with voltage peaks out of range of the over voltage safety relay shunt system.

The boys to talk to on this would be at OUTBACK if they are still in business.

When engineering at Trace, saw Xantac, the hwang-ho new buyer, looming on the horizon, they bailed and were dispersed throughout the industry.

An inverter overload output faulting into square wave can theoretically over-amp the input but for the protection fuses. A Timothy Leary shaped input waveform could theoretically throw the control section into an epileptic fit.

IMHO again, full load battery charge mode input waveform should be analyzed on a scope or scope meter.

Gawd, I wanna scope meter....baaaad....

[mike-s]

To understand why, remember that the S in RMS is square. When you square a negative number, the result is positive. So, even though the waveform looks like the upper one, the RMS measurement sees it like the lower one (like it's been full wave rectified)...

So, there's your 170 V peak voltage, and your 120 V RMS voltage. But when you measure peak to peak on the actual signal, it's double the peak voltage which RMS "sees."

[mike-s]

MrWizard wrote:
What you are saying is over double what I remember being taught
Iirc its around 171~172v peak to peak
120v is the RMS value

340p-p is way to high
This would result in a line voltage over 240vac

I think you are thinking of a 230/250v service line

Nope, I meant what I said. Peak to peak voltage for standard 120 VAC is about 340 V. Perhaps you're thinking of peak voltage, which is half that. P-p is much easier to measure with an o-scope, especially when it's a sine wave.

Google it if you don't believe.

[MEXICOWANDERER]

Forgive me.
I am laughing too hard to reply...

[BFL13]

Vector inverter manual says its MSW has an RMS voltage of 115, "which is the same as household power." It then explains that most AC voltmeters get the average value of the waveform, so they read 20-30 volts "low" when on MSW.

[MrWizard]

What you are saying is over double what I remember being taught
Iirc its around 171~172v peak to peak
120v is the RMS value

340p-p is way to high
This would result in a line voltage over 240vac

I think you are thinking of a 230/250v service line

[mike-s]

MEXICOWANDERER wrote:
The value of oscilloscope waveform confirmation. Sigh. If the waveforn of the gen inverter allows for 200 volts peak to peak it may drive the Magnum insane. Same for Hz

If the output were only 200 V p-p, the generator would be defective, it's impossible to have 120 VAC RMS with only 200 V p-p. It would be way under voltage. For a sine wave, 120 AC would be around 340 p-p. A 25% duty cycle MSW output would be the same.

[MEXICOWANDERER]

The value of oscilloscope waveform confirmation. Sigh. If the waveforn of the gen inverter allows for 200 volts peak to peak it may drive the Magnum insane. Same for Hz

[pianotuna]

Well,

I don't have to worry about the Magnum not charging properly.

I got lucky and had the Magnum and the generator turned off as I was going to be gone for a while.

I came back to soot on the wall above the unit.

I've let out the magic blue smoke.

[MEXICOWANDERER]

Yup, and hopefully the TVS and MOVs will provide that 10-30 ms buffer.

Wuwu! La Dentista is a real looker! Any distraction in a storm, they say...

[pianotuna]

Hi Mex,

I hope the tooth fairy will ease your pain.

I find that switching is fast enough on the Sola Basic that voltage jumps up before the air conditioner compressor motor makes a sound and before the fan has even started to turn. I was pleasantly surprised that was the case.

Obviously, the Sola cannot deal with millisecond voltage excursions, which is why I want to do some surge suppression.

MEXICOWANDERER wrote:
First of all let's trash some garbage information...

3. A weak point in stepped MEXICAN autoformer voltage control, is it takes time for the device to switch from one step to the next. Sudden line surges can raise (or lower) voltage by the percentage of boost (or sag) built into the transformer switching system. The switching has to have hysterisis to prevent stitching chattering.

[MEXICOWANDERER]

First of all let's trash some garbage information...

1. Comision federal de Electricidad operates on a national standard of 127vac 60Hz and 254 Vac dos hilos and tres hilos (single and three phase). The only time they drop line voltage sans L0 neutral is when the customer provides their own transformer which regs demand to be a "Y" connection meaning 4 taps, one being L0.

2. An autoformer absolutely can raise or lower AC voltage values. But there is no true isolated secondary. The biggest fault of the autoformer versus a true 2 windings transformer is line ISOLATION. True isolation not only demands a 2 winding (not common leg connected) transformer, but an earth ground barrier to eliminate cross channel contamination. The isolation is expressed in db.

3. A weak point in stepped MEXICAN autoformer voltage control, is it takes time for the device to switch from one step to the next. Sudden line surges can raise (or lower) voltage by the percentage of boost (or sag) built into the transformer switching system. The switching has to have hysterisis to prevent stitching chattering.

4. Not only do I actually operate 3 buck boost autotransformers like Pianotuna's I own four Sola ferroresonant line regulators, the largest being 3.1 Kw, which has a secondary full 38 db isolation transformer. This is all being done on CFE power.

5. I have never experienced a prolong overvoltage condition with a Tor Rey autotransformer as fast acting fuses are mounted in the faceplate of the autotransformer and they will fail if the unit is over-amped.

6. I found it helpful to study line voltge output of the Tor-Rey and also the Sola units using a oscilloscope. The first 8 or so ms of step transition incurs a slightly warped waveform with no prominent spikes or sags.

7. Whenever a product promises "Automatic" anything, it means that other performance values can be affected as well. This "shotgun" approach of automation is one of the largest reasons I utterly shun products that attempt to think for me. Such products commonly incorporate the word "smart".

8. Oh goodie, after waiting two and a half weeks, today is the day I drive 155 miles for a root-canal. Tiny as it is, the compensation is to save the tooth and the bill is eqvt to $137.00 A bad point is epinephrine-free Novocaine is not available down here and my heart may not like this at all. And people wonder why some of my responses are so grumpy. Well so be it. If epinephrine raises my pulse to 400 I'll be the first to know.