Problems with Standby generator (240V 15Kva)

[Rod Out Back]

Folks,

I wondered if anyone might be able to point me in the right direction
here...

I live in outback Australia. Electricity grid power is 240v 50Hz. We
have a (2nd-hand) 15Kva (Single Phase) standby generator which kicks
into gear if the grid power fails. It runs until the power control
unit detects grid power, and then switches back over to grid power
after the grid has been on for a set amount of time(currently 10
minutes). At this point, the genset shuts down.

Genset is a 2cyl Lister/Petter diesel motor driving a McCaul brushless
alternator. Unit is rated for 15Kva, and I understand the previous
owner was a telecommunication company; using the genset to maintain a
battery bank in a large telephone exchange.

Problem: While the genset is running, we have a very noticeable
flicker in the lights. The flicker varies in intensity, and seems to
be related to the load the alternator is under.
If I put about a 5-7 kilowatt load on the alternator, the flicker
nearly dissappears. I am wondering if the alternator has been adjusted
to suit a constant, heavy load in it's previous life, and that the
light loading is causing me the flicker.

Possible causes as I see it:

Engine speed. This one is easy to fix, and I suppose the easiest to
check. I do have an optical tachometer here, which can tell me if it
is running at 1500rpm. However, I note that the last time I checked
power to the house when the genset was running, it was pretty close to
the correct voltage(I think it was 248 volts with light load).
However, it makes me wonder if the engine revs are set a little to
high?? Or would a too low setting cause the same?

Alternator control board. I can get another unit if this one is
flakey, but there is an adjustment on the board to adjust output (cant
remember exact adjustment), and I wonder if this has been adjusted for
a constant heavy load. I wondered if the light/intermediate loading
from the house is causing me grief.

Unfortunately, I dont have a local genset whizz that I can call, and I
expect I will have to resolve this one myself.

Apologies if this is posted to the wrong group, but I wondered if
anyone had encountered similar problems with standby generators.

Any thoughts or suggestions gratefully accepted.


Cheers,

Rod.....Out Back

 

[You]

This is a one cylinder
unit, correct? Suchs units are highly efficient, but have more cyclic
variation in speed than multicylinder units.

When was the last time you EVER heard of a single Cyl, 30 Hp, Engine?
Somebody isn't smelling the coffee here. Most of the Lister/Petter Twins
will do 12Kw, but 15 would be a stretch. The three cyl Lister/Petters
are normally what is used for 15 Kw gensets. With a brushless genend,
one should look at the Droop Setting, and Mechaical Governer Stability
adjustments first. (How much does the RPM drop from No Load, to Full
Load, and what does the output voltage do while doing the test)

 

[Rod Out Back]

Thanks for the note. Actually, it looks like it might be either a 3 or 4
cylinder unit:
http://www.maesco.com/products/hp/hp_diesel/hp_diesel.html#0-20aircooled
http://www.sommersgen.com/pages/diesel6to32.htm

Robert,

Many thanks for the reply. I am still getting around to testing some
of the suggestions made to try to weed out the possible problem, but
it is on long list of other issues to be done at present....

The motor (as stated in my original post) is a 2-cylinder
Lister/Petter diesel, driving a 15Kva alternator. From what i can
read in electrical conversions, this equates to a 12.75 Kilowatt
alternator.

Thanks again for your ideas.


Cheers,

Rod.....Out Back