TOT Petrol generators

"Dave Saville" wrote in message
...
Having a disabled wife and the dire predictions of coming power
outages this winter I thought I might get a petrol genny to keep the
gas fired CH going and maybe the deep freeze. I realise it would be a
manualy change over.

Any recomendations? I guess the startup current of a CH pump and
freezer is not much.

TIA

I am dependent on electricity for an oxygen concentrator and was encouraged
to have my details placed on the Priority Services Register. There isn't a
"National" Register - it is related to the area of your electricity
supplier. A starting point is
http://www.consumerfocus.org.uk/get-...able-consumers

--
JohnT

"Bill Wright" wrote in message
...
Get a Honda. They are supurb. Definitely don't get one that doesn't use
the DC to inverter method.

I hadn't realised that petrol generators generate low voltage DC and then
invert it to 240V sine wave. I'd always assumed that they generated 240V AC
right from the generator - ie that they were alternators rather than
dynamos.

On Thu, 7 Nov 2013 15:04:38 -0000, "NY" wrote:

"Bill Wright" wrote in message
...
Get a Honda. They are supurb. Definitely don't get one that doesn't use
the DC to inverter method.

I hadn't realised that petrol generators generate low voltage DC and then
invert it to 240V sine wave. I'd always assumed that they generated 240V AC
right from the generator - ie that they were alternators rather than
dynamos.

I didn't know that either. But it does make sense. For an alternator to
produce a 50cycle/sec output it needs a speed regulator to ensure that
it rotates at the same speed at all times regardless of the load.

--
Peter Duncanson
(in uk.tech.digital-tv)

On 07/11/2013 15:04, NY wrote:
"Bill Wright" wrote in message
...
Get a Honda. They are supurb. Definitely don't get one that doesn't
use the DC to inverter method.

I hadn't realised that petrol generators generate low voltage DC and
then invert it to 240V sine wave. I'd always assumed that they generated
240V AC right from the generator - ie that they were alternators rather
than dynamos.

There *are* some which use alternators, but the voltage output and
frequency of these are far less stable than inverter-based models.
--
Cheers,
Roger
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On 07/11/2013 14:00, charles wrote:
In article , Chris Hogg
wrote:
On Thu, 07 Nov 2013 13:29:59 +0000 (GMT), charles
wrote:

In article ,
wrote:
On Thu, 07 Nov 2013 11:19:08 +0000, Chris Hogg wrote:

On Thu, 7 Nov 2013 09:32:21 +0000 (UTC), "Dave Saville"
wrote:

Having a disabled wife and the dire predictions of coming power
outages this winter I thought I might get a petrol genny to keep the
gas fired CH going and maybe the deep freeze. I realise it would be
a manualy change over.

Any recomendations? I guess the startup current of a CH pump and
freezer is not much.

TIA

Not got one, but have you thought of a power inverter running off the
car? That's assuming you've got a car, and can get it close enough to
the house to run extension leads etc. See http://tinyurl.com/ov4m2d4
and pick one with the power you think you might need.

I've looked at that too. Problem is that for any decent output they
take a very heavy load from the car (just calculate the amps!), so you
have to keep the engine running for what could be many hours. Apart
from that the alternator isn't really designed for continuous heavy
loading.


In a BBC survey vehicle, using 2 inverters to power mains operated
equipment, I managed to use nearly a full tank of petrol (18 gallons) in
8 hours.

I don't doubt it. But petrol generators don't run on fresh air (well,
they do in a manner of speaking, but they also need petrol). How much
petrol would a petrol generator have used in producing the same amount of
power in that time?

I don't know, but the comment was to suggest that using your car engine to
run an inverter was not a very good idea. Cheap on capital cost, but
horrible running costs.


Bear in mind that there is legislation about storing petrol in domestic
premises.

DOn't store too much or (a) you will then require a petroleum spirit
licence along with fire precautions to comply and (b) the lack of (a)
will invlaidate your house insurance.

A diesel generator avoids these two issues.

Stephen.

"Stephen" wrote in message
...
Bear in mind that there is legislation about storing petrol in domestic
premises.

DOn't store too much or (a) you will then require a petroleum spirit
licence along with fire precautions to comply and (b) the lack of (a) will
invlaidate your house insurance.

A diesel generator avoids these two issues.

Ah, is diesel not classed as "petroleum spirit" for the purposes of fire
safety regulations? I'd always assumed that although it's not "petrol" it is
still "petroleum spirit" because it is still derived from crude oil and is
still highly flammable: though much harder to ignite because it is less
volatile and so produces much less flammable vapour, it burns once it has
been ignited.

Do diesel generators require less voltage and frequency regulation because
the greater low-end torque means that the engine revs will be less affected
by electrical load and therefore mechanical force to turn the generator?

I've heard it said that diesel machinery (generators, lawn mowers etc) can
actually be quieter than petrol because although inherently noisier when run
at the same speed as petrol (the characteristic diesel clatter of the fuel
ignition) diesel generates more torque so can be run at a lower speed with
higher gearing to the appliance that is being driven.

"Dave Saville" wrote in message
...
Having a disabled wife and the dire predictions of coming power
outages this winter I thought I might get a petrol genny to
keep the
gas fired CH going and maybe the deep freeze. I realise it
would be a
manualy change over.

Any recomendations? I guess the startup current of a CH pump
and
freezer is not much.


Contact your electricity supplier. If a customer has a medical
need they should provide you with some sort of back-up. Talk to
the CAB and/or OfGen as they may be able to help.


--
Woody

harrogate three at ntlworld dot com

On Thu, 07 Nov 2013 17:32:39 +0000, Roger Mills
wrote:

On 07/11/2013 15:04, NY wrote:
"Bill Wright" wrote in message
...
Get a Honda. They are supurb. Definitely don't get one that doesn't
use the DC to inverter method.

I hadn't realised that petrol generators generate low voltage DC and
then invert it to 240V sine wave. I'd always assumed that they generated
240V AC right from the generator - ie that they were alternators rather
than dynamos.

There *are* some which use alternators, but the voltage output and
frequency of these are far less stable than inverter-based models.

You both seem to have gotten the wrong end of the stick. The inverter
models are a recent innovation (iirc, introduced by Honda about a
decade back - notably that EU 3000 unit I mentioned).

By far the majority of the much cheaper commodity standby generators
are of the classic alternator type where the frequency is directly
dependent on the prime mover's rpm (3000/3600 rpm for the cheapest 2
pole 50/60Hz alternator designs). In this case, the throttle
controller is purely a speed regulator designed to hold the rpms to
within +/- 3% of the nominal speed.

The inverter isn't your typical 12VDC to 230Vac design but is more
usually a 170 or 340vDC to 115/230Vac type which obviates the need for
a transformer and associated losses (2 to 5% depending on loading).

Furthermore, the alternator uses a permanently magnetised rotor
(which eliminates a 2.5% or so excitation loss) followed by a
switching regulator (if this can't be entirely accomodated within the
design of the inverter itself due to voltage rating limitations of the
powerFET devices chosen).

Unlike the direct 50/60Hz single phase alternator, the PM generator
used in the inverter type can be a 200 / 400 volt version of the car
alternator designs (3 phase fullwave rectified output) but without
field excitation losses.

For a given load, the output voltage is in direct proportion to the
rpm so any voltage regulation has to be done by an external switching
regulator (whether seperate or built into the inverter) and is usually
aided by throttle control which can usually be optionally programmed
for economy if the load can tolerate the short dips of voltage that
may arise as extra loads are switched on during the brief time
required for the throttle controller to bring the generator rpms up to
the higher speed required.

Not only do you have the extra cost of the inverter, you also have
the extra complication of throttle control of voltage and output power
so it should come as no surprise that this type are considerably more
expensive than the older traditional designs (typically 3 to 10 times
more expensive for units in the 2 to 3KVA output range - much more
expensive than the actual components costs can possibly justify in
this day and age).

The main advantages of the modern inverter type are the better fuel
economy, quieter running and, perhaps most importantly, the absence of
overvolting hazard on capacitive loads (modern electronic equipment
loads).

Bill's recommendation for the inverter type is well founded but
rather spoilt by the horrendously high pricing of even the relatively
cheap Hyundi 3KVA model (just shy of 600 quid plus VAT).

HTH & HAND
--
Regards, J B Good

Johny B Good wrote:

The main advantages of the modern inverter type are the better fuel
economy, quieter running and, perhaps most importantly, the absence of
overvolting hazard on capacitive loads (modern electronic equipment
loads).

That was all very interesting and informative.


Bill's recommendation for the inverter type is well founded but
rather spoilt by the horrendously high pricing of even the relatively
cheap Hyundi 3KVA model (just shy of 600 quid plus VAT).

Worth the extra cost though, if you can afford it. I know the Hondas do
seem to keep their value quite well. They are sought after as s/h good
by the likes of radio hams.

Bill

HTH & HAND

On 07/11/2013 19:44, Johny B Good wrote:
On Thu, 07 Nov 2013 17:32:39 +0000, Roger
wrote:



There *are* some which use alternators, but the voltage output and
frequency of these are far less stable than inverter-based models.

You both seem to have gotten the wrong end of the stick. The inverter
models are a recent innovation (iirc, introduced by Honda about a
decade back - notably that EU 3000 unit I mentioned).

By far the majority of the much cheaper commodity standby generators
are of the classic alternator type where the frequency is directly
dependent on the prime mover's rpm (3000/3600 rpm for the cheapest 2
pole 50/60Hz alternator designs). In this case, the throttle
controller is purely a speed regulator designed to hold the rpms to
within +/- 3% of the nominal speed.

The inverter isn't your typical 12VDC to 230Vac design but is more
usually a 170 or 340vDC to 115/230Vac type which obviates the need for
a transformer and associated losses (2 to 5% depending on loading).

Furthermore, the alternator uses a permanently magnetised rotor
(which eliminates a 2.5% or so excitation loss) followed by a
switching regulator (if this can't be entirely accomodated within the
design of the inverter itself due to voltage rating limitations of the
powerFET devices chosen).

Unlike the direct 50/60Hz single phase alternator, the PM generator
used in the inverter type can be a 200 / 400 volt version of the car
alternator designs (3 phase fullwave rectified output) but without
field excitation losses.

For a given load, the output voltage is in direct proportion to the
rpm so any voltage regulation has to be done by an external switching
regulator (whether seperate or built into the inverter) and is usually
aided by throttle control which can usually be optionally programmed
for economy if the load can tolerate the short dips of voltage that
may arise as extra loads are switched on during the brief time
required for the throttle controller to bring the generator rpms up to
the higher speed required.

Not only do you have the extra cost of the inverter, you also have
the extra complication of throttle control of voltage and output power
so it should come as no surprise that this type are considerably more
expensive than the older traditional designs (typically 3 to 10 times
more expensive for units in the 2 to 3KVA output range - much more
expensive than the actual components costs can possibly justify in
this day and age).

The main advantages of the modern inverter type are the better fuel
economy, quieter running and, perhaps most importantly, the absence of
overvolting hazard on capacitive loads (modern electronic equipment
loads).

Bill's recommendation for the inverter type is well founded but
rather spoilt by the horrendously high pricing of even the relatively
cheap Hyundi 3KVA model (just shy of 600 quid plus VAT).


So which bits of what I wrote are you disagreeing with?
--
Cheers,
Roger
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Please reply to Newsgroup. Whilst email address is valid, it is seldom
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