Brand new inverter generator dies with suddenly applied full load, runs it fine if loaded gradually 3

[LMF5000]

I bought a brand-new Zipper ZI-STE1200IV on eBay (from Germany, no idea who the OEM of the unit is, but it's identical to the Parkside PGI-1200A1 generator sold in the UK).

The specs claim 1200W for 5 seconds and 1000W continuous output. I've been testing it with one of those halogen heaters that have 3x 400W heating elements. The brightness of the heating elements gives a good indication of the output voltage (faster than any digital meter can measure). I also have an inline power meter attached and a tachometer that takes its signal from a sense wire wound around the spark plug cable.

Here's the story:
1. If I turn on a 400W heating element, the revs fall, the voltage droops, then it picks up and delivers full voltage no problem
2. If I turn on the second 400W heating element, the revs fall slightly voltage drops slightly, then it picks up and delivers 800W. I even turned on the third 400W element and it managed to supply all 1200W.
3. If it's idling and I turn on both 400W elements at once (800W sudden load), most of the time the generator struggles, the revs drop, and the engine dies of low revs. Looking at what the throttle servo is doing during this time, it doesn't move when the load is first switched on (throttle remains in "idling" position, around half-open). As the engine starts bogging down over the next 2 seconds, the throttle barely opens. When the engine is really struggling it opens the throttle fully, at which point it finally dies. The engine is impossible to hand-start at this point (throttle full open) without full choke.

In addition to the above, it hunts a little (revving up and down) when cold at no load, and it over-revs for a few seconds every time a load is removed.

Any ideas what the problem could be?

 

[Skogsgurra]

Now, when you have fixed it. Does it do what you expected it to do in your first posting?

I mean, is it now possible to connect the 3x400 W heater without problems? I still think that the generator will have a problem with that and that there wasn't any problem with the binding servo.

Why do I ask? Because the generator behaved the way I would expect it to behave and since the servo worked when you applied 400 and 800 and, finally, 1200 W. The problem seems to be the unexpected loading and nothing in the genset as such.

We could learn from knowing what the real problem was.

Gunnar Englund

http://www.gke.org

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Half full - Half empty? I don't mind. It's what in it that counts.

 

[LMF5000]

Sorry for the late response, for some reason I don't get email notifications of replies :/

BrianPetersen - Thank you . Ordinarily a good course of action, but I'm in Malta and this was shipped from Germany. Sending it back (if the seller agreed it was a problem) would have cost at least €25. Not worth it when the whole thing cost €180. Plus the original reason for buying it was to have a small engine to tinker with to gain some knowledge. The generator is just an added bonus It will only ever be used when the power goes out (very rare here) and to power things in a remote garage of ours with no electrical connection (utility company charges €60 per year for connection - this genset will basically pay for itself in 3 years).

DanEE - it runs all 3 400W elements at the same time. Sure under those conditions it sounds like the little engine is working as hard as it can, and the throttle is almost fully open, but I did repeatedly take it up to 1200W in 5-second bursts with no issues. Right now the most challenging load seems to be a 20W led floodlight. It floors the generator in ways that are inconsistent with its power. The gen would be driving a 400W or 800W load just fine, but the output collapses to 140-180V the instant I connect the floodlight and recovers a second or two later. I'm going to do some testing with a power meter later today to try and understand things better.

Skogsgurra - I think initially it had a fuelling problem. And I suspect it was due to metal filings in the tank. You see, the screw holes for the handle were tapped right into the metal of the tank (with an additional doubler for rigidity), thus leaving small pieces of metal in the tank from the tapping operation. I saw this when I first inspected the tank after opening the box. I did my best to clean out the pieces with air and then rinsing the tank with clean petrol, but I suspect I didn't get all of them. If one of the iron particles made its way to the carb jets it could've caused my issues. Perhaps it was dislodged when I sprayed carb cleaner and got rid of when I opened the drain screw to the carb float bowl to get clean petrol into the carb. I can't really say. The engine is running much better now that it has 2.8 hours of runtime on it, but it still misses a few strokes on idle.

On the very plus side, last weekend I managed to start a 1600W (rated) vacuum cleaner on it, by careful manipulation of the speed knob on the vacuum. It starts up with the knob at around 50% power. Surprisingly, turning the knob down to the lowest setting makes the motor stall and stop spinning for some reason. No idea why. Motor sounds like a universal motor (with brushes) based on the sound it makes when slowly revving up (generator only outputs 140V or so with stalled vacuum cleaner plugged in; voltage slowly rises as motor spools up).

 

[OperaHouse]

I have a small old ONAN 400W generator I use at my camp that is efficient. When I want to run the vacuum I plug it into a buck transformer made from an old UPS with just the transformer inside. Half the outlets are 100V and the rest are 90V. The generator is that old that the standard voltage was 110. That manages to just run the vacuum with a universal motor. Since you are running heaters, dropping the voltage slightly with a buck transformer could be the solution for some loads.

 

[itsmoked]

You want to learn about small engines.. I'll help. A while ago I told you not to solve your linkage binding issue
by leaving a carb nut loose. Since that is exactly what you've seemed to do, in a short while that nut will get
looser yet until an air leak occurs. Air will rush in thru that leak causing a lean burn to occur which will lead
to a burned exhaust valve and a holed piston. It will occur under load and happen in mere seconds. You need to fix
the linkage correctly.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Skogsgurra]

LMF5000
Can you load it with those 3x400 W heaters now? Not gradually, but all at once? That was, if I remember right, your original problem. I must confess that I would be surprised if that works now.

Gunnar Englund

http://www.gke.org

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Half full - Half empty? I don't mind. It's what in it that counts.

 

[cswilson]

We have sometimes used a bank of light bulbs as a test load for our inverters, knowing that the initial current surge is a challenge to handle.

A couple of years ago, I got curious just how the filament resistance changed with loading, and therefore temperature. I got the following results for a nominal 40W (120V) standard incandescent bulb:

0V: 26.2 ohms (multimeter measurement)
30V: 170.0 ohms (voltage and current measurements)
60V: 251.8 ohms (ditto)
90V: 312.7 ohms (ditto)
120V: 361.7 ohms (ditto)

So the resistance at the rated voltage is about 14 times the off resistance. A halogen incandescent light bulb operates at a higher temperature and would have an even higher ratio.

Now, lamps used for heating would have a lower operating filament temperature because they don't need to be hot enough to produce a lot of visible light, but I would still expect a ratio greater than 10.

The current surge would be very short, because filaments generally have a thermal time constant of about 1 second, but the surge is still very real.

Curt Wilson
Omron Delta Tau

 

[itsmoked]

LMF5000; Your generator's weird behavior with the LED light is a result of a 'cheap' generator's poor voltage
regulator. The regulator is being confused by the highly non-linear distortion caused by an equally cheap LED
floodlight. The regulator is seeing short current draw spikes and thinking they are the average current draw.
This can be avoided in your case by getting a better LED flood light, one that is advertised to have PFC, or
Power Factor Correction.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[EdStainless]

Or by adding filtering caps to the LED flood power supply.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

[LMF5000]

Itsmoked - I didn't leave a carb nut loose, it was one of the silver self-tapping screws holding the stepper motor in place on the throttle horn (see the pics in an earlier post of mine - they're the ones that screw the white plastic tray that holds the stepper motor). If they loosen the worst case scenario is that the servo motor detaches from the throttle and the engine over-revs and destroys itself I guess (unless they've implimented an ignition-cut rev limiter somewhere).

Skogsgurra - the initial problem was loading with 2x400W elements on. Now I can do that without problem. The best test though was switching on a 1000W load (the fan heater test in the youtube video I posted in an earlier reply). I have since tested with all 3 elements on (1200W total), and it worked. I've also run a 1600W vacuum cleaner (at half-power, actual inline power meter indicates a flow of about 960W steady-state).

cswilson and others - the engine used to cut out a few seconds after the heater was turned on, when the halogen lamps were already glowing incandescent, so it wasn't a problem of the initial surge current being too high, it was a problem of the engine not being able to catch up with the load and deliver sufficient torque to hold revs under the load. Still not sure what it was, though reassembling the stepper motor and spraying carb cleaner seemed to help. Perhaps as the engine is still very new the rings haven't had time to bed-in either. The performance seems to be improving with time.

 

[Skogsgurra]

LMF
That is kind of amazing. A rotating generator (without an inverter) would do that. But if an inverter catches up and delivers when the load (cold) is way, way higher than rated load and manages to heat the elements into glow and higher resistance is really good. Especially at the price that you paid for the device.

I think that drive system manufacturers have something to learn there.

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[LMF5000]

Thanks . It actually cheats a little in that the instant the load is turned on, the inverter output voltage falls below the required 233V - I've measured as low as 130V connected to a stalled vacuum cleaner.

Power factor/wattage measurements for those who asked earlier (using the 240V mains AC supply, not the generator):
"20W" LED floodlight - 16.8W @ PF 0.56

1600W Vacuum cleaner:
Lowest speed setting - 719W @ PF 0.57
Medium speed setting - 940W @ PF 0.69 (this is the setting at which the vacuum actually spools up with my generator)
Maximum speed setting - 1350W @ PF 0.95

No wonder it didn't start up on the lowest setting - the apparent power is 719/0.57 = 1261 VA (when running on mains)! In fact the generator engine wouldn't even rev up, it would just put 130V across its output and the vacuum wouldn't spin (I guess the inverter is not sensing the load). I couldn't measure the power factor in this state (vacuum locked rotor) because my power meter shuts down at such a low line voltage.