North Australian FISH FINDER TM forums

Hello

The big thing with portable generators is the type of 50 cycle waveform they generate. Some are awful and an Engel or similar won't run at all. These generators are the $300 specials which use an electronic circuit to produce a square wave-form which motors, sensitive electronic circuits and some battery charges don't like at all.

A new generation of generators has arrived in which the wave-form has been modified to approximate a pure sine wave. These are called modified-sine-wave generators. Most devices will run ok on them and these are represented by the middle market series of "inverter" or silent generators of $600-$1000 for 2kva or so.

Pure sine-wave generators will run anything but u pay more for them.

Hence Honda prices.

So apart from electical peace of mind the other consideration is reliability.

The middle $ range modified sine wave generators will suit most applications.

The onl;y real consideration after that is capacity. Gennies are quoted in KVA. Usually peak output.
However, that's not the real measure. Different loads produce different problems for the generator. Peak KVA is calculated into a resitive load.

Bit of goobledegook following:
Most loads are whats called reactive loads (inductive lagging or capacitive leading causing a phase difference between volts vand amps with the phase angle determining power factor)

Rated KVA is calculated into a real load and is usually less than peak kva due to what's called power factor. Ignoring what power factor actually is we only need to know what it does.

A pure resitive load has a power factor of 1. Anything else has a power factor less than 1.

Rated (real) output = peak x pf.

Example a 2kva (peak) gennie working into a load with a power factor of .8 is rated at .8 x 2 = 1.6 rated (real) power.

Do the maths with any of the gennies u can find the specs on.

The other thing is noise.
Most produce noise between 50db and 65db ay 7 metres distance. There doresn't seem to be much by way of numbers betwee say 59db and 65 db.

But there sure is. 1db difference in sound level is the min change that the human ear can detect. 6 db more noise is TWICE the noise level. 6db less noise is HALF the noise level.
The measurement standards are at 7 metres and at either low/no load or full load. Assume full load and watch out for anything over 60db! Best thing to look for on a gennie is the EU appropval mark.

regards
Ronj

Thanks Ronje , you have just explained more to me than any salesmen could have hoped to do , cheers

UNCLDUG

The hardest thing to do is attempt to explain technical things in simple words.

The gennie marketing people aren't silly. Its a technical product and can be confusing to a prospective purchaser. The salesman can then " finish the sale off". A buyer assumes that the salesman knows it all ('cos he's selling the bl..dy things). That's normally not true.

Over the last couple of years gennie users have become more knowledgeable and u hear terms like KVA, inverter gennies and db being thrown around.

To take advantage of this the marketing people worked out that users were starting to understand about inverters etc. The (dare-I-say-it) grey nomads have been responsible for the developments in gennies, power supplies, battery chargers and solar. The db noise ratings are directly targetting campers in parks and other places where noise can be a problem. Probably not a problem for isolated places where u go.

But it all adds to the confusion.

The most significant thing that the gennie marketing people realised was that users were starting to understand that " gennies ain't gennies - Sol". (remember the oils-ain't oils Sol ads a few years ago?"). Buyers were starting to look for gennies with inverters!

The ones with pure sine wave inverters were more expensive and had an "i" in the model number. eg Honda 20i(i understand that these have pure sine wave output.).

Manufacturers gave buyers sine wave inverters. Pretend ones!! Called modified-sine-wave inverters.

The marketing people followed up by putting an i on the gennie models with the "pretend" sine wave inverters too. No good asking the salesman which one you're interested in. Chances are that he won't know either.

Do u have an e-mail address?

I'd like to ask your opinion about something. I don't know how to do an attachment on a pm.

regards
Ronj

Fellas,
I may be out of line but has anyone considered using a surge/spike protection power board to run sensitive equipment off the generator? Just a thought...
Cheers,
John.

Hi John

U're not out of line at all. It wasn't my post.

Good idea to reduce effects of spikes. Any filters or protecters can only be of benefit.

The post came up as a general comment about how complicated and misleading sales info and gennie specs can be. And we,ve got to make a purchase decision based on what we're told.

regards
Ronj

ronje wrote:Hello

The big thing with portable generators is the type of 50 cycle waveform they generate. Some are awful and an Engel or similar won't run at all. These generators are the $300 specials which use an electronic circuit to produce a square wave-form which motors, sensitive electronic circuits and some battery charges don't like at all.

A new generation of generators has arrived in which the wave-form has been modified to approximate a pure sine wave. These are called modified-sine-wave generators. Most devices will run ok on them and these are represented by the middle market series of "inverter" or silent generators of $600-$1000 for 2kva or so.

Pure sine-wave generators will run anything but u pay more for them.

Hence Honda prices.

So apart from electical peace of mind the other consideration is reliability.

The middle $ range modified sine wave generators will suit most applications.

The onl;y real consideration after that is capacity. Gennies are quoted in KVA. Usually peak output.
However, that's not the real measure. Different loads produce different problems for the generator. Peak KVA is calculated into a resitive load.

Bit of goobledegook following:
Most loads are whats called reactive loads (inductive lagging or capacitive leading causing a phase difference between volts vand amps with the phase angle determining power factor)

Rated KVA is calculated into a real load and is usually less than peak kva due to what's called power factor. Ignoring what power factor actually is we only need to know what it does.

A pure resitive load has a power factor of 1. Anything else has a power factor less than 1.

Rated (real) output = peak x pf.

Example a 2kva (peak) gennie working into a load with a power factor of .8 is rated at .8 x 2 = 1.6 rated (real) power.

Do the maths with any of the gennies u can find the specs on.

The other thing is noise.
Most produce noise between 50db and 65db ay 7 metres distance. There doresn't seem to be much by way of numbers betwee say 59db and 65 db.

But there sure is. 1db difference in sound level is the min change that the human ear can detect. 6 db more noise is TWICE the noise level. 6db less noise is HALF the noise level.
The measurement standards are at 7 metres and at either low/no load or full load. Assume full load and watch out for anything over 60db! Best thing to look for on a gennie is the EU appropval mark.

regards
Ronj

Awesome stuff Ronj... ..