I have got a generator (Generac BSP7500LE) connected to my house (Via a
proper transfer switch!)
When running from this generator, there is a very noticeable flicker on the
lights all the time.
I have a tester, and it tells me the voltage is 230v and 49.8Hz when the
generator is loaded at about 10A - what am I getting this flickering on the
lights, and can I do anything to stop it!?
I have three UPS' on various computer equipment, and they seem happy with
the generator's supply.
Probably your waveform is nothing like sinusoidal.
Most equipment should cope OK with this.
Do you have a 'scope you could check the waveform with? (Assuming you
know how to do this safely of course - don't even attempt it if you
Why would you expect this ? A generator is an electromagnetic machine
with a great big iron core. There's little in there to cause harmonics
and there's a great bit LR filter to damp them out. Inverters are your
culprits for angular waveforms, not electrical machines.
In my almost negligible experience, flicker from generators has usually
been caused by switching in crude electromechanical regulators.
I have the same phenomenon with filament bulbs running off my 6KVA 2 pole
generator (3000rpm). Its because the generators speed is not actually
constant due to there only being a power stroke every 4 revolutions of the
crank and the lack of adequate inertia in the rotating mass to maintain the
speed- thus you;re not getting a proper sinusoidal waveform.
1500rpm (4 pole) or 960 rpm (6 pole) alternators or even the new crop of
inverter-generators dont generate this flicker.
Mine doesnt want to know. :( Its a Belkin . Dont know why, the supply volts
& hz are within tolerance on the box. Any ideas?
On 8 Sep 2005 08:59:25 GMT, email@example.com (Huge) wrote:
OK then - can I blame Belkin for my big pile of failed USB hubs ?
They're firmly on my list of suppliers from whom I'll never willingly
buy another product.
I might even _admire_ their chutzpah in selling gold-plated carrot
embossers through Dixons. But why should I want to buy such a product ?
I've sometimes run a 2000VA UPS off a 2200VA generator
(I know...). The UPS takes a good long look at the
generator output, and when it's happy it switches over.
The generator sees the sudden load and its speed drops,
and the voltage with it. The UPS doesn't like this, and
disconnects. The generator speed shoots up. Hunting
To start the whole business I've taken to resting a finger
on the generator's governor until the UPS switches over,
forcing the speed very slightly high. That's enough to stop
the UPS dropping out, and it'll run until it's out of fuel.
I reckon a generator engine needs a gurt big flywheel. But
at least I can drag this one around. Honda sidevalve, made
in Thailand. I dread to think when it was designed but it
starts on the first pull every time, no matter how many
years it's been lurking without attention in the shed.
I'd be interested to hear the true answer. Its not wave shape, a
filament lightbulb can run off any wave shape, and with the power level
varying at 100Hz (which is what you get on a 50Hz supply) the filament
will smooth it all out no problem.
The lighting flicker you see on gennies sometimes is at much lower freq
than 50Hz, so the genny's output must be in some way modulated at a
lower frequency. I dont know what the cause is, but the only likely
candidate I can think of is the control circuitry, the regulator, where
one is fitted.
If youre determined to get rid of the problem, there are 2 solutions,
excluding genny replacement.
1. changing to CFLs will help, as their output varies much less with v.
Traditional fluorescents ditto.
2. Putting big reservoir caps on the CFLs will wipe out the problem
completely. Full wave rectify the power to the bulb socket and add your
big cap there. It will be compatible with all CFL and filament bulbs
then. Note youre not allowed to do with with screw in holders, since it
leaves both connections live.
I get the feeling I have explained not very well here...
I agree. The genny will have an AVR module (automatic voltage
regulator) which senses the AC output voltage and adjusts the (DC)
current in the field windings to stabilise the output. Thus there's a
negative feedback loop involved and all the usual loop dynamics and
stability issues are present. If the loop is underdamped and there's a
varying load on the genny you get 'hunting' of the o/p voltage, which is
exactly the "modulation" you describe.
No, I doubt the OP's 3000rpm small petrol Genny will have an AVR, it'll just
have a passive system of a cap and 2 diodes in the field winding. My 6KVA
Only the vastly more expensive larger 3000rpm and 1500rpm sets will be
equiped with an active electronic AVR, which do keep the volts more stable,
especially if they are 'slugged' somewhat. This doesnt help the frequency
though unless its fitted with an electronic throttle. (i.e. 40kva and bigger
Damn, they don't take paypal :-(
Moving on a bit, I'm interested in the running costs of your
genny's. How many kW/h do you guys reckon to get to the gallon
(or pint?) from a 5-6kVA unit (petrol or diesel)?
. never trust a man who, when left alone ...... Pete Lynch .
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