Pulsing lights

[dwellselectric]

So we installed a 12kvw generator about a year ago. We went back to the house today to replace a dimmer and he as a question for us and my boss didn't know what to tell him. Perhaps you guys might have an answer. Well the HO told us that he started up his generator and wanted to see how far he could take the generator before the breaker on the generator would trip. So he puts on all the lights in the house and the generator sounded fine. Than he puts on one a/c unit and the generator was fine. Put on the 2nd one and the generator was still fine. He put on his 3rd A/C unit and he said the the lights in the house started to pulse. Go dim than wicked bright and so on. He asked my boss why that was and the breaker didn't trip. Any ideas guys?

 

[Rampage_Rick]

Gererator can't supply enough continuous current to trip the breaker? It sounds like he's lugging the engine and as such he'd get a 'brownout' at which point one or more of the A/Cs might shed it's load, causing the voltage to come up, as well as the RPM to jump due to a smaller load, causing even higher voltage. A/C draw returns, and dance steps repeat. I'd suggest a bigger generator (me thinks you have a 20hp now)

This is why you always run electronics through a line-interactive UPS off a generator when you have non-fixed loads. I've fried some large APCs off a generator, but spared $30,000 worth of gear

 

[dereckbc]

Simple the generator cannot supply enough current to trip the breaker with load only. Only way for it to trip is from an instanious fault.

 

[Denis]

load applied, engine slows, lights dim, govenor kicks in, max fuel, extra voltage, load applied, engine slows, lights dim, govenor kicks in, max fuel,.......

 

[don_resqcapt19]

Dereck,

Simple the generator cannot supply enough current to trip the breaker with load only. Only way for it to trip is from an instanious fault.

Many small generators can't come close to providing enough current for an instantaneous trip. The breaker is just for looks.
Don

 

[weressl]

So we installed a 12kvw generator about a year ago. We went back to the house today to replace a dimmer and he as a question for us and my boss didn't know what to tell him. Perhaps you guys might have an answer. Well the HO told us that he started up his generator and wanted to see how far he could take the generator before the breaker on the generator would trip. So he puts on all the lights in the house and the generator sounded fine. Than he puts on one a/c unit and the generator was fine. Put on the 2nd one and the generator was still fine. He put on his 3rd A/C unit and he said the the lights in the house started to pulse. Go dim than wicked bright and so on. He asked my boss why that was and the breaker didn't trip. Any ideas guys?

Voltage regulator can't keep up with the inrush current that the cranking AC units demand, actual continuous or even momentary load could still below the breaker trip curve. The breaker in this case may be enough for short citcuit protection, but not overload protection.

 

[charlie tuna]

most generators and their prime movers are designed to produce proper rated output voltage and frequency up to 80 per cent load ---above that and up to 100 per cent load --these rated output perameters are going to decrease. consider what happens in an a.c. circuit when you decrease the frequency--total resistance to current flow decreases proportionally-- remember the formula---total resistance= 2 times the constant "pie" times two times impeadance times "frequency"...... and as the resistance decreases---current increases causing the voltage to decrease---thus the lamps dim!!! remember to educate people with generators --- too many appliances installed in today's homes have computerized circuits in them and these circuits are effected by "poor power" even though they are not operating. consider a new side-by-side refrigerator. the base circuit board controlling the refrigerator's operation is powered by a low voltage power supply --- when operating at a frequency of 52 cycles the current through this board can be double it's normal operating current. i had a customer burn up three boards ---the first one was under warentee---the last two weren't. they cost $525. each!!!! all three failures were after power outages where he ran his home on his new back up generator. microwaves--ranges-dishwashers-big screen t.v.'s all are exposed to line voltages even though they are not in use.....

 

[brian john]

All you have to do is listen to the engine. It tells the complete story.

As stated not only is the voltage dropping but it is most likely surging upon recovery prior to sagging again.