It is currently 29 Mar 2024, 09:02

Generator advice please

This is the place to go with all your issues, questions or handy hints on all things related to motors, electrickery, engineering, metalwork etc...

Re: Generator advice please

Postby novocaine » 22 Jul 2021, 10:47

think spiky. we want nice smooth flowing curves to our AC wave. what a generator kicks out (it's an alternator on an enginer at the end of the day) is a spiky, jumps around the place wave.

yes they can be cleaned up, you jam it through a sinewave inverter or a voltage regulator.
Carbon fibre is just corduroy for cars.
novocaine
Old Oak
 
Posts: 2560
Joined: 26 Nov 2020, 10:37
Name: Dave

Re: Generator advice please

Postby 9fingers » 22 Jul 2021, 10:57

Andyp wrote:Anyone like to explain dirty lecky? And can it be cleaned for aforementioned sensitive equipment?

At I guess I would imagine that TVs would be classed as sensitive.


There will be dips and surges in frequency with matching voltage variations.
Usually the engine speed control is done by a crude vane and spring in the airflow from the fan in a similar way to a lawn mower and you are possibly familiar with they way they "hunt"
It is not practical to clean these up properly - about all that might be able to be done is to limit the maximum voltage.
If you need a clean supply then buy an inverter based generator they are far far more advanced and have the ability to throttle back the inverter engine speed when the load is less than 100% so more economical and quieter.
The two types are chalk and cheese.

As for what loads are sensitive and those less so, anything with electronics in - and that include led lights these days- it is a matter of how well the loads are designed for over voltage tolerance.
You will possibly have heard about normal grid surges taking out electronic items and a poorly regulated genny could be far worse.

For my sensitive stuff I use a UPS with big leisure batteries, then a 1kw inverter generator and lastly a dirty genny for things like refrigeration.
Maybe OTT But I recall the 8 days we had without power after the 1987 gales with a few month old baby to care for.
That was not fun!

Bob
Information on induction motors here
https://drive.google.com/file/d/1dBTVXx ... sp=sharing
Email:motors@minchin.org.uk
User avatar
9fingers
Petrified Pine
 
Posts: 10038
Joined: 21 Jul 2014, 20:22
Location: Romsey Hampshire between Southampton and the New Forest
Name: Bob

Re: Generator advice please

Postby AJB Temple » 22 Jul 2021, 11:19

The generator is unable to maintain a consistent smooth output and so the amplitude of the sine wave varies. An inverter generator (as one alternative) generates AC, which is converted to DC, and then inverted to deliver AC with a smooth sine wave with little variation in amplitude. But this adds complexity and cost, and generally the power out put £ for £ is much less. There are advantages to inverters, such as being able to throttle back for small loads (quieter and more fuel economy).
Don't like: wood, engines, electrickery, decorating, tiling, laying stone, plumbing, gardening or any kind of DIY. Not wild about spiders either.
User avatar
AJB Temple
Sequoia
 
Posts: 5433
Joined: 15 Apr 2019, 09:04
Name:

Re: Generator advice please

Postby novocaine » 22 Jul 2021, 11:30

AJB Temple wrote:The generator is unable to maintain a consistent smooth output and so the amplitude of the sine wave varies. An inverter generator (as one alternative) generates AC, which is converted to DC, and then inverted to deliver AC with a smooth sine wave with little variation in amplitude. But this adds complexity and cost, and generally the power out put £ for £ is much less. There are advantages to inverters, such as being able to throttle back for small loads (quieter and more fuel economy).


the conversion within an inverter is interesting as it's typically a digital conversion, so you still don't get a smooth sine wave but a PWM (turn it of and on quickly with a mosfet) sine wave that's made up of lots of little steps. the smaller the steps, the more it costs. the inverter isn't the bit that throttles the engine as such, there is additional control circuitry that is monitors the converted DC (because DC is easier to watch digitally) and adjust accordingly to maintain a constant output. it's really clever, but when it goes wrong it is normally terminal.

there is a bit more to it than just controlling the engine speed, the alternator produces a dirty wave to as it's not a perfect AC as the move inside the magnetic field, so you get fluctuations in the lead and lack of the sign wave that result in a more of a sawtooth wave profile. modern electronics really hate this.
Carbon fibre is just corduroy for cars.
novocaine
Old Oak
 
Posts: 2560
Joined: 26 Nov 2020, 10:37
Name: Dave

Re: Generator advice please

Postby 9fingers » 22 Jul 2021, 11:43

AJB Temple wrote:The generator is unable to maintain a consistent smooth output and so the amplitude of the sine wave varies. An inverter generator (as one alternative) generates AC, which is converted to DC, and then inverted to deliver AC with a smooth sine wave with little variation in amplitude. But this adds complexity and cost, and generally the power out put £ for £ is much less. There are advantages to inverters, such as being able to throttle back for small loads (quieter and more fuel economy).


Adrian, Earlier you mentioned about some "inverter" types the were not true inverters. I've not met these before. Are they an intermediated class of genny or just dishonest advertising?

Bob
Information on induction motors here
https://drive.google.com/file/d/1dBTVXx ... sp=sharing
Email:motors@minchin.org.uk
User avatar
9fingers
Petrified Pine
 
Posts: 10038
Joined: 21 Jul 2014, 20:22
Location: Romsey Hampshire between Southampton and the New Forest
Name: Bob

Re: Generator advice please

Postby Andyp » 22 Jul 2021, 12:17

Dave, Bob & Adrian thanks for the explanations.

Fortunately, although we have frequent outages, maybe a half dozen per year, they do not last long enough to cause issues with the fridge nor freezer. We have a bottled gas hob and can heat most of the house from the wood burner so no need at present for a genny.
I do not think therefore I do not am.

cheers
Andy
User avatar
Andyp
Petrified Pine
 
Posts: 11719
Joined: 22 Jul 2014, 07:05
Location: 14860 Normandy, France
Name: Andy

Re: Generator advice please

Postby spb » 22 Jul 2021, 12:26

9fingers wrote:Adrian, Earlier you mentioned about some "inverter" types the were not true inverters. I've not met these before. Are they an intermediated class of genny or just dishonest advertising?

There's an intermediate class that use AVR - Automatic Voltage Regulation. I don't fully understand the how yet, but it's a solid state device that regulates the alternator output voltage by changing the voltage going in to some part of it. The upshot is that it can react much faster to load changes than the conventional method using the engine throttle and generally stays within 5% of the target voltage. It isn't as spot on as an inverter type, but good enough for most things.
spb
Nordic Pine
 
Posts: 569
Joined: 27 Sep 2020, 20:25
Location: Cambridge
Name: Stephen

Re: Generator advice please

Postby 9fingers » 22 Jul 2021, 12:45

Ah Ok thanks Adrian

An AVR can indeed react quicker that the "lawn mower" speed regulator.
AVR is electronic and so to the ignorant seller could be confused with an inverter as another electronic option.
I guess if an inverter is claimed and yet is cheap it is probably AVR.

Bob
Information on induction motors here
https://drive.google.com/file/d/1dBTVXx ... sp=sharing
Email:motors@minchin.org.uk
User avatar
9fingers
Petrified Pine
 
Posts: 10038
Joined: 21 Jul 2014, 20:22
Location: Romsey Hampshire between Southampton and the New Forest
Name: Bob

Re: Generator advice please

Postby AJB Temple » 22 Jul 2021, 13:44

I was referring specifically to the Bohmer-AG brand actually, that pretends it is made in Germany but is in fact Chinese. It claims to be a true inverter, but I have read material that suggests this is not true and that it is much closer to an AVR.

Was very tempted by the Hyundai 4000i. which is a true inverter and gets excellent reviews. This is about £800. But first I will try the Honda as a simple solution to my sump pump needs.
Don't like: wood, engines, electrickery, decorating, tiling, laying stone, plumbing, gardening or any kind of DIY. Not wild about spiders either.
User avatar
AJB Temple
Sequoia
 
Posts: 5433
Joined: 15 Apr 2019, 09:04
Name:

Collected my genny today

Postby AJB Temple » 25 Jul 2021, 23:10

Picked up the used and reconditioned genny today. Honda GX390 with various industrial accoutrements was a bit bigger and heavier than I expected and only just squeezed into the Tesla.

I thoroughly recommend buying from Pete as recommended to me above. https://petepowerblog.wordpress.com

He is very funny and a mine of information. Reminds me a lot of Fred Dibnah. Also has a lovely Colchester lathe (mid sized. 290?)

Knows a lot about generators and everything there is to know about Honda engines.

He's based in Barton Mills near Bury St Edmunds. Nice little village but if you go there I do NOT recommend the nice looking Bull Inn for lunch unless you enjoy being barked at by a really stroppy lady in charge who seemingly has forgotten she is in the hospitality industry.
Don't like: wood, engines, electrickery, decorating, tiling, laying stone, plumbing, gardening or any kind of DIY. Not wild about spiders either.
User avatar
AJB Temple
Sequoia
 
Posts: 5433
Joined: 15 Apr 2019, 09:04
Name:

Re: Collected by penny today

Postby novocaine » 26 Jul 2021, 07:45

AJB Temple wrote:Picked up the used and reconditioned genny today. Honda GX390 with various industrial accoutrements was a bit bigger and heavier than I expected and only just squeezed into the Tesla.


Please, oh please tell me you have a picture of your lovely tesla with a gert big petrol generator stuck in the back of it? even better, please tell my you chucked the charge cable in for a laugh? ;)
Carbon fibre is just corduroy for cars.
novocaine
Old Oak
 
Posts: 2560
Joined: 26 Nov 2020, 10:37
Name: Dave

Re: Collected by penny today

Postby RogerS » 26 Jul 2021, 08:06

novocaine wrote:
AJB Temple wrote:Picked up the used and reconditioned genny today. Honda GX390 with various industrial accoutrements was a bit bigger and heavier than I expected and only just squeezed into the Tesla.


Please, oh please tell me you have a picture of your lovely tesla with a gert big petrol generator stuck in the back of it? even better, please tell my you chucked the charge cable in for a laugh? ;)


Yes... :eusa-think: I guess that IS one way to assuage range-anxiety :lol:
If opportunity doesn't knock, build a door.
User avatar
RogerS
Petrified Pine
 
Posts: 13291
Joined: 21 Jul 2014, 21:07
Location: Nearly finished. OK OK...call me Pinocchio.
Name:

Re: Generator advice please

Postby AJB Temple » 26 Jul 2021, 13:48

:D Nope

He was a bit surprised when I turned up in a Tesla, but the more suitable Q7 needs taxing for the road as we put stuff on SORN during covid lockdown.

Not sure if I could charge the car from the Genny. Usually I charge it free (300miles at a go) at the supercharger near use whist doing the shopping.
Don't like: wood, engines, electrickery, decorating, tiling, laying stone, plumbing, gardening or any kind of DIY. Not wild about spiders either.
User avatar
AJB Temple
Sequoia
 
Posts: 5433
Joined: 15 Apr 2019, 09:04
Name:

Previous

Return to Engineering - Electrical/Metalworking

Who is online

Users browsing this forum: No registered users and 2 guests