Inverter versus 12v

[mick88]

Does running a 240V fridge through an inverter from a 12v battery bank have a
far greater drag on the batteries, than running an equivalent size 12v fridge?

Cheers, Mick.

[67hardtop]

F

[Mick_Marsh]

Yes.
You are adding the power losses of the inverter which, at times, can be quite high.

Oh, Rod, this isn't facebook.

[67hardtop]

Thanks Mick. I wasnt sure how id keep tabs on this one coz its a subject id like to know more on. Cheers

[101RRS]

Yes what does F mean?

As Mick said inverter losses can be substantial particularly with big inverters. Also 240v fridges dont have to worry about minimising power usage for cooling capacity so generally a 240v fridge will use more power than a 12v fridge for the same cooling ability.

I recently looked at this for the 3 way in my camper. 12v fridges were either too small or too big to fit into the slot so I looked at using the correct size 240v bar fridge to fit the slot for use with an inverter. Overall 240v fridges used half again the power of similar sized 12v fridges so as well as the increased power usage from the inverter you need to take into account the power use of the 240v fridge.

Garry

[67hardtop]

F means Following......its a fb thing. I got confused

[Mick_Marsh]

Thanks Mick. I wasnt sure how id keep tabs on this one coz its a subject id like to know more on. Cheers

Just above the top post, there is a menu bar. The left most drop down, that is in about the middle, is "Thread Tools". Click on that and select "Subscribe to this Thread". You can then follow all your subscribed threads by listing your subscribed threads by selecting "Subscribed Threads" under "Quick Links" in the top toolbar.

You can even set up to be notified if there is a post in that thread.

[67hardtop]

Thanks Mick. Im using aulro on my phone. Ive found a tick symbol in a white round circle. It says subscribe to this topic...lol...or unsubscribe if u select it again...hehehe...

[JDNSW]

To go back to the original question....

The answer is ... it all depends. The power used through an inverter will be the power used by the refrigerator multiplied by 100/E, where E is the percentage efficiency of the inverter at the output current needed to run the refrigerator. This efficiency typically varies widely according to the output, but is often quoted for an inverter as a single figure, mostly (you guessed it) the highest efficiency, which is usually close to maximum output. So high power inverters, running at low output are typically inefficient, perhaps as low as 70% or less, where their best figure is over 90%.

But this is not the whole story. There are a limited range of 12v refrigerators, but a far wider range of 240v ones, although if you need a small physical size, 240v ones tend to be less efficient, and "bar" fridges, for some reason tend to be very inefficient. While the fact that they run off batteries tends to encourage manufacturers of 12v units to make their devices efficient, mandatory labelling and energy efficiency laws tend to do the same for 240v manufacturers.

[Mick_Marsh]

Oh, and fridges cycle on and off. Inverters are constantly drawing power.
So, the inverter is drawing power even when the fridge isn't.

[Milton477]

Are we talking about an inverter fridge which runs off 12v with it's own inbuilt inverter or a 12v / 240 vac fridge with a separate inverter which can also power other appliances in the setup?

[trout1105]

I can see the advantage of using an inverter for one of those 12v, 240v Gas fridges because to be completely honest the 12v option on these types of fridges that are often fitted to caravans are pretty useless and will only attempt to keep things cool at best.
The 240v option is quite good on these types of fridges so while the van is being recharged via the trucks alternator the extra power usage via the inverter wouldn't be an issue.
For the normal 12v/240v fridges (Engel, Waco etc.) the 12v is just as good as the 240v option so there is No advantage in using an inverter to power them.

[Geedublya]

I can see the advantage of using an inverter for one of those 12v, 240v Gas fridges because to be completely honest the 12v option on these types of fridges that are often fitted to caravans are pretty useless and will only attempt to keep things cool at best.
The 240v option is quite good on these types of fridges so while the van is being recharged via the trucks alternator the extra power usage via the inverter wouldn't be an issue.
For the normal 12v/240v fridges (Engel, Waco etc.) the 12v is just as good as the 240v option so there is No advantage in using an inverter to power them.

I think a lot of the problem with using 12v is because the wiring and connectors are under rated. On my previous Goldstream and my current Jayco I have re-wired the 12v to the fridge using updated cables and better connections. Now I have to be careful what I put in the fridge when on 12v as it often goes below zero and frozen lettuce and cucumber isn’t great even when defrosted.

[Tombie]

F means Following......its a fb thing. I got confused

No. It’s a lazy FB thing..

Even on FB a simple tap in the top corner and select “turn on notifications”

Just like you can do in this forum!

[DeanoH]

Are we talking about an inverter fridge which runs off 12v with it's own inbuilt inverter or a 12v / 240 vac fridge with a separate inverter which can also power other appliances in the setup?

Not quite sure what you're getting at here. :confused:

There are two basic types of fridges.

The compressor fridge such as your common or garden variety household fridge and your typical Engel/Waeco 'camping' fridge. The difference between these is that the household fridge uses a 240 volt AC motor to drive the compressor and the Engel/Waeco uses a 12 volt DC motor to drive the compressor. Your typical camping fridge also has either an internal or external 240 volt AC to 12 volt DC power supply (a bit like a battery charger) to allow operation from the mains.

The other type of fridge is an absorption type fridge that uses heat to operate. These are your typical 3 way fridges (though can also be a 2 way fridge) eg. Dometic, Finch etc. These use an electrical heating element (12 volt DC or 240 volt AC) and/or a small gas flame as the heat source.

There are advantages and dis advantages with either system but with cheap solar and efficient design IMO compressor type fridges are by far the better choice for touring/off roading.

I've not come across a fridge with a built in inverter.

Deano :)

[Homestar]

Mick, what sort of fridge are we talking about? An Engel or something like that or an older 3 way 240/12/gas or you thinking about using a 240 only fridge? (don't do that).

[DeanoH]

Had a chat with another Oka owner today and he was extolling the virtues of inverter fridges. It seems that inverter fridges (as in inverter air conditioner technology) are being made now by LG/Samsung for example and are reputed to be very electrically efficient.

Deano :)

[Homestar]

Had a chat with another Oka owner today and he was extolling the virtues of inverter fridges. It seems that inverter fridges (as in inverter air conditioner technology) are being made now by LG/Samsung for example and are reputed to be very electrically efficient.

Deano :)

Just had a quick Google to look at specs. Couldn’t find a small one with specs but a 450 litre unit runs at around 300KW per year - bloody good going for a fridge that size. If a 160 litre unit used say half that it would be easy to run of a decent battery and solar system. The one I looked at was under $1000 too so a third of the price of a new 3 way of similar capacity. [emoji106]

[trout1105]

Do these inverter fridges take the absolute pizzling that the engel's and Waco's do?

[Homestar]

Doubtful, but we're talking about a bus in this instance or a decent sized caravan - both of which would make a fridge like this last without issue.

[mick88]

Just had a quick Google to look at specs. Couldn’t find a small one with specs but a 450 litre unit runs at around 300KW per year - bloody good going for a fridge that size. If a 160 litre unit used say half that it would be easy to run of a decent battery and solar system. The one I looked at was under $1000 too so a third of the price of a new 3 way of similar capacity. [emoji106]

What Brand was it/they that you looked at please Gav?
It seems that this type of technology in fridges is starting to take in motorhomes and caravans from what I can gather looking at MH sites/forums.


Trout, as for standing up to a flogging like an Engel can take, well that's definitely not going to happen.

Cheers, Mick.

[Homestar]

It was a Samsung unit - will put a link up tonight when I’m at my computer.

[Tinggu]

Just seen this thread so I apologise if it's been thrashed to bits already. IMHO it is always better to use 12V direct rather than through an inverter. Unless there is amazing new technology - which is always expensive - inverters gobble an awful lot of power whether they are feeding a unit or not. Can expect a 1A draw with no load. As the fridge is expected to cycle for a few minutes at a time with long periods of rest that amounts to a lot of wasted battery resource.

[bee utey]

Just seen this thread so I apologise if it's been thrashed to bits already. IMHO it is always better to use 12V direct rather than through an inverter. Unless there is amazing new technology - which is always expensive - inverters gobble an awful lot of power whether they are feeding a unit or not. Can expect a 1A draw with no load. As the fridge is expected to cycle for a few minutes at a time with long periods of rest that amounts to a lot of wasted battery resource.

Better quality inverters (e.g. Selectronic) go into sleep mode when not under load and draw bugger all power.

[trout1105]

I carry 2x inverters, a small one I think it is only 200-300w that I use to power or recharge my laptop and a larger 2kva unit I carry in case I need to do some emergency welding on the track and this has come in very handy on the Useless Loop road sticking my boat trailer mudguards back on that the corrugations are determined to remove.
I have used both inverters when camped up and the smaller unit doesn't seem to drag too much out of the batteries, The 2kva unit however is pretty power hungry so it obviously isn't one of those units that will power down when not in use.
I imagine that these new inverter type fridges would come with a fairly small inverter that powers down when not in use But is there any Real advantage using these types of fridges over a normal 12v/240v fridge?

[Homestar]

Better quality inverters (e.g. Selectronic) go into sleep mode when not under load and draw bugger all power.

Yep, I have a Selectronic unit - brilliant bit of kit. Once the load drops below a pre set load - mine is selectable between 4, 8, 12 and 16 Watts for 15 seconds, it goes to sleep and uses around 50mA when asleep. As soon as a load is applied it kicks back in instantly. When I’m out in the van, I never turn it off - it does it all for me.

It’s the cheap Chinese units you need to watch out for.

[Nmritchie]

As others have said

Use a 12v fridge with a reputation for efficiency.

Inverters have losses, that is why they have cooling fans, and unless they are the type that goes to sleep, draw power even when no 240 power is being used.

I am getting an inverter wired into my camper trailer, and it will be turned on by a switch beside the inverter power point, with a warning led to show it is ON. The switch operates a relay to provide power to the inverter. The intent is to only have the inverter powered when we need power at the power point. Some larger inverters come with a remote switch, but a basic relay will do the same job.

If possible, add extra insulation in the fridge cabinet on the sides to minimise heat flowing in through the fridge walls. Also ensure that the fridge condenser is well ventilated. Heat buildup around the condenser both increases heat inflow which makes the fridge cycle ON more, and also reduces the refrigeration cycle efficiency. A recent study of household compressor fridges showed that power consumption tripled when “room” temperature increased from 20 to 40 degrees C. That is around a 15% increase in power usage for each degree hotter. If you can add a small computer fan of say 3 watts to assist the convection flow up the back of the fridge and out, that comes on with the compressor, the small extra power used by the fan will significantly reduce overal fridge power usage.

[DrDeath]

As the other guys have said:
Less efficient electrics as no need to be so careful with power,
Poorer insulating techniques as no need to be so careful with power,
Large electrical losses in the inverter, converting ELV DC to LV AC.

Also further mechanical and heat (ie energy) losses in the fridge motor if the inverter is a ‘modified square wave’, as the ‘sharp edges’ create magnetic eddies and mechanical jitter etc etc. (the mech is probably too subtle to be felt by us, but you can feel the heat)

But also, I understand that the domestic fridge motor is not designed to cope with non-level or moving operation. The fridge fluid slops around the sump, doesn’t lube the pump properly, or allow smooth or proper pumping.

Thats why certain portable fridge makers extol the virtues of ‘swing’ motors etc.

Hope this helps,
cheers

[Old Farang]

Had a chat with another Oka owner today and he was extolling the virtues of inverter fridges. It seems that inverter fridges (as in inverter air conditioner technology) are being made now by LG/Samsung for example and are reputed to be very electrically efficient.

Deano :)
I have a Samsung Inverter fridge in my house. No idea how much power it has saved, but after around 18 months there has been no problem with it. The inverter has a 10 year warranty and it cannot be heard running.

These units are VFD, the same as a room air conditioner. SOME of them can be run off a 240 volt external inverter, but NOT all of them. Beware!

How the Digital Inverter Compressor Has Transformed the Modern Refrigerator – Samsung Global Newsroom (https://news.samsung.com/global/how-the-digital-inverter-compressor-has-transformed-the-modern-refrigerator)

[Mick_Marsh]

I carry 2x inverters, a small one I think it is only 200-300w that I use to power or recharge my laptop and a larger 2kva unit I carry in case I need to do some emergency welding on the track and this has come in very handy on the Useless Loop road sticking my boat trailer mudguards back on that the corrugations are determined to remove.
I have used both inverters when camped up and the smaller unit doesn't seem to drag too much out of the batteries, The 2kva unit however is pretty power hungry so it obviously isn't one of those units that will power down when not in use.
I imagine that these new inverter type fridges would come with a fairly small inverter that powers down when not in use But is there any Real advantage using these types of fridges over a normal 12v/240v fridge?
Despite the name, the inverter technology in fridges aren't what is generally accepted as an inverter. They are actually VSDs (varable speed drives). 240V AC at 50Hz is fed into the fridge. In the VSD, this AC voltage is converted to DC which is then converted to a frequency to drive the compressor motor at variable speeds.

[trout1105]

Despite the name, the inverter technology in fridges aren't what is generally accepted as an inverter. They are actually VSDs (varable speed drives). 240V AC at 50Hz is fed into the fridge. In the VSD, this AC voltage is converted to DC which is then converted to a frequency to drive the compressor motor at variable speeds.

If these fridges need 240v to run and can't simply be plugged into a 12v system then I can't see any advantages over the regular 12v/240 fridges.

[Old Farang]

Despite the name, the inverter technology in fridges aren't what is generally accepted as an inverter.

It may not be to you, but the industry accepted nomenclature is inverter. Also the variable speed is called variable frequency drive. (VFD) as I have posted above. A variable speed drive is an entirely different piece of equipment.

[Mick_Marsh]

It may not be to you, but the industry accepted nomenclature is inverter. Also the variable speed is called variable frequency drive. (VFD) as I have posted above. A variable speed drive is an entirely different piece of equipment.
Depends on which brands.
Variable Speed Drives (VSD) (http://www.teco.com.au/variable-speed-drives-vsd)
They do the same thing.

They can also be referred to as VVVF drives.

Oh, I am in the industry. I used to work for a company that sells them. I now work for a company that uses them. Anything from 0.5kW metering pumps to 530kW drives. I've worked on projects that use much larger VSDs.

[mike123]

I would go 12v fridge option. I installed a 12v Waeco 115 litre upright fridge freezer in a shack off grid. It was new but a factory second (slight dent in door). It wasn't 3 way and very specific for 12v - basically it wasn't trying to be all things to everyone. Key was getting a fridge with a good quality compressor and correct sized wiring to hook it up.

We were also running a 1300watt inverter but we used that for charging hand held 2 way, cordless drills, mate's fridge/cooler when visiting, satellite internet and a toaster.

It was important for us to preserve the batteries (off several solar panels) as in winter we may not see the sun for 5 days at a time. Using a 240v fridge would be too much drain on our batteries IMHO.

[Pedro_The_Swift]

Theres two words you dont see together very often,,
satellite internet and toaster[bigrolf]

[mick88]

Glacio produce a few 12v 24v 240v model of digital inverter fridges at reasonable prices.

Also on the inverter subject, would it take a very big inverter to run either one of those infa-red, or induction type cooktops that are all the go today?
Has anyone given this a go?
I am not a big fan of gas appliances in caravans/campers, so I am looking at options.


Cheers, Mick.

[trout1105]

I would imagine that the Electric cooktops would draw a heap of power much the same as the microwave, air con, kettle and toaster would so you would need a decent sized inverter to run them along with a large solar array/battery bank to power them.
Personally I hate cooking on electric stoves and ovens and much prefer to use gas for this.
Gas is more efficient than electricity to cook with and even the 3 way fridges run much better on gas

[bee utey]

Also on the inverter subject, would it take a very big inverter to run either one of those infa-red, or induction type cooktops that are all the go today?
Has anyone given this a go?
I am not a big fan of gas appliances in caravans/campers, so I am looking at options.


Cheers, Mick.

There's only one way to find out, buy one:

5-Star Chef Electric Induction Cooktop Portable Kitchen Cooker Ceramic Cook Top 9350062008744 | eBay (https://www.ebay.com.au/itm/5-Star-Chef-Electric-Induction-Cooktop-Portable-Kitchen-Cooker-Ceramic-Cook-Top/351434683439?epid=809539384&hash=item51d323b42f:g:xxwAAOSwA4Ba8F8A)

Rated power adjustable from 300W to 2000W, should do something at that price. [smilebigeye]

[JDNSW]

Basically, anything that heats uses a lot of power! Toaster, microwave and jug aren't too bad, because they are typically only used for a few minutes.

[Old Farang]

Glacio produce a few 12v 24v 240v model of digital inverter fridges at reasonable prices.

Also on the inverter subject, would it take a very big inverter to run either one of those infa-red, or induction type cooktops that are all the go today?
Has anyone given this a go?
I am not a big fan of gas appliances in caravans/campers, so I am looking at options. Cheers, Mick.
Infrared and induction cooking or heating are two entirely different methods. What is overlooked with both of them is the Power Factor when using them on an inverter supply. You MAY get away with an infrared heater as they are more of a resistive load. An induction heater by definition has a very low PF as it is basically a coil of wire and works like a transformer. I would not even attempt to use any inductive device on an inverter unless the PF of the load is known. The wattage load advertised does not take into account the PF, and at a low PF such as 0.5 the actual wattage that the inverter has to produce is twice what is being used by the load, known as "wattless current".

[Homestar]

Induction cooktops use HUGE power - one I installed at a friends house needed 30amps total. That's over 7KW - and as mentioned, the power factor is horrendeous so without a pan on the stovetop there's a lot of VAR's to consider too. Even with one plate running you'd need ennormous battery bank to cook a meal. The ebay jobby shown uses 2KW for one plate - remember you'll need it for at least half an hour or so to cook a meal. That's over 160 amps continuous from your batteries - the cabling would need to be pretty good too.

Infrared are a little better but still huge power draw and unfortunately unrealistic to run off batteries and an inverter. Love it or hate it, gas is the only economical way of having a decent cooktop. You could use a Coleman dual fuel stove, but if carrying flamable stuff around bothers you, that's no good either.

Could run a genset while you're cooking and do it ok though.

[Old Farang]

Depends on which brands.
Variable Speed Drives (VSD) (http://www.teco.com.au/variable-speed-drives-vsd)
They do the same thing.

They can also be referred to as VVVF drives.

Oh, I am in the industry. I used to work for a company that sells them. I now work for a company that uses them. Anything from 0.5kW metering pumps to 530kW drives. I've worked on projects that use much larger VSDs.

This may not be the correct thread to discuss this, so please move if it offends any rules.
I post it as general interest, and not trying to teach anyone to suck eggs.
…………………………………………� �…………………………………………� ��.
Bearing in mind your signature line Mr. Marsh:

I served a 5 year apprenticeship as an electrical fitter / armature winder when such training was done under the "old system", which tended to include a big sized boot! It was a commercial repair shop where we rewound and overhauled everything from electric shavers up to 500 hp motors from a coal mine. Generators, pumps, automotive, the electrical side of refrigeration, the local farmers electric fence unit, and on and on!

Following that I spent years of self study and night school obtaining marine engineers certificates, some of it while working on ships with both DC and AC systems.

I have been chief electrician on a DP Drillship that employed an automated power management system long before computers and PLC's were used. I have been chief engineer on a conventionally moored diesel electric Drillship, all of this over more than 30 years. None of this is in anyway bragging, just posted to establish where I am coming from.

The oil drilling industry has, for more years than I like to remember, used variable speed drives (VSD) Every one of them used DC traction motors in various roles such as draw works, mud pumps, rotary table, etc. The standard DC motor employed is the same motor as used in locomotive diesel electric engines, nominal 800hp.Some of them are made by EMD and others by GE.

Although the DC motors have changed very little over the years, the control systems certainly have. Have you had any experience with a Ward Leonard System? What about a magnetic amplifier and saturable reactor? Some of these systems had absolutely no AC connection, apart maybe from the prime mover. Earlier types employed DC generators with various control systems, to drive the DC motors, more common in later years were SCR drives. Some of these systems were also employed in electric cargo cranes. If you have never had the dubious pleasure of working on a LeTourneau PCM 120 electric crane I can assure you it was definitely a VSD!

All they do have in common is that they are VSD and used to control DC motors.

The onlyvariable speed AC motor that I have seen is a "Schrage", used mostly in the carpet and yarn making industry, and it is termed a VSD.

A common simple VSD is a Singer Sewing Machine with a foot control, a true VSD that works on both AC and DC if a universal motor.

By definition ,an "inverter' is changing a DC source to AC. There are several methods employed to achieve it. Briefly, if you want to supply the device with AC then it is designed to firstly convert the AC to DC before "inverting" it back to AC. The frequency of the AC depends on the design. If you are going to run it off a battery or other DC supply, then it only has to "invert" the designed voltage to AC and at whatever frequency required. The thing to watchout for with this is if the output is a pure sine wave, or a"modified" sine wave, which is more a "square wave" and not suitable for some equipment, especially electronics.

A variable frequency drive (VFD) just employs more electronics to alter the output frequency.Most, not all, also control the output voltage. In which case it is termed a VVVF. In any case, whatever it is termed it is an "inverter", not a VSD.

It could be argued that all of this is just semantics, but it is not. A VFD in whatever form, is a much more sophisticated piece of equipment than any VSD. And that is even before getting into such deviations as "vector drive".

Just to avoid any more typing, a simple reference:

https://www.metroid.net.au/engineering/vsd-vfd-vvvf-whats-difference/

Happy camping!

[Mick_Marsh]

This maynot be the correct thread to discuss this, so please move if it offends anyrules.
I post itas general interest, and not trying to teach anyone to suck eggs.
…………………………………………� �…………………………………………� ��.
Bearing inmind your signature line Mr. Marsh:

I served a5 year apprenticeship as an electrical fitter / armature winder when such trainingwas done under the "old system", which tended to include a big sizedboot! It was a commercial repair shop where we rewound and overhauled everythingfrom electric shavers up to 500 hp motors from a coal mine. Generators, pumps,automotive, the electrical side of refrigeration, the local farmers electricfence unit, and on and on!

Followingthat I spent years of self study and night school obtaining marine engineerscertificates, some of it while working on ships with both DC and AC systems.

I have beenchief electrician on a DP Drillship that employed an automated power managementsystem long before computers and PLC's were used. I have been chief engineer on a conventionally mooreddiesel electric Drillship, all of this over more than 30 years. None of this isin anyway bragging, just posted to establish where I am coming from.

The oildrilling industry has, for more years than I like to remember, used variablespeed drives (VSD) Every one of them used DC traction motors in various rolessuch as draw works, mud pumps, rotary table, etc. The standard DC motor employedis the same motor as used in locomotive diesel electric engines, nominal 800hp.Some of them are made by EMD and others by GE.

Althoughthe DC motors have changed very little over the years, the control systemscertainly have. Have you had any experience with a Ward Leonard System? Whatabout a magnetic amplifier and saturable reactor? Some of these systems had absolutelyno AC connection, apart maybe from the prime mover. Earlier types employed DCgenerators with various control systems, to drive the DC motors, more common inlater years were SCR drives. Some of these systems were also employed in electriccargo cranes. If you have never had the dubious pleasure of working on a LeTourneau PCM 120 electric crane I can assure you it was definitely a VSD!

All they dohave in common is that they are VSD and used to control DC motors.

The onlyvariable speed AC motor that I have seen is a "Schrage", used mostlyin the carpet and yarn making industry, and it is termed a VSD.

A commonsimple VSD is a Singer Sewing Machine with a foot control, a true VSD thatworks on both AC and DC if a universal motor.

By definition,an "inverter' is changing a DC source to AC. There are several methods employedto achieve it. Briefly, if you want to supply the device with AC then it isdesigned to firstly convert the AC to DC before "inverting" it back toAC. The frequency of the AC depends on the design. If you are going to run itoff a battery or other DC supply, then it only has to "invert" thedesigned voltage to AC and at whatever frequency required. The thing to watchout for with this is if the output is a pure sine wave, or a"modified" sine wave, which is more a "square wave" and notsuitable for some equipment, especially electronics.

A variablefrequency drive (VFD) just employs more electronics to alter the output frequency.Most, not all, also control the output voltage. In which case it is termed aVVVF. In any case, it is termed an "inverter", not a VSD.

It could beargued that all of this is just semantics, but it is not. A VFD is a much more sophisticatedpiece of equipment than any VSD. And that is even before getting into suchdeviations as "vector drive".

Just toavoid any more typing, a simple reference:

VSD, VFD, VVVF? What’s The Difference? - Metroid Electrical Engineering (https://www.metroid.net.au/engineering/vsd-vfd-vvvf-whats-difference/)

Happycamping!


Thankyou for that link you provided.
Just before the description of the VVVF drive, you'll see the words, and I'll quote from the article here,:

Most commonly, the terms VFD and VSD are interchangeable.

[DrDeath]

Who’d have thought Landies could provoke such marvellously interesting and learned electrical and semantical (?ish) discussions !

But then, I spose they stimulated the invention of steam, winches and tow trucks ...

I’m just a closet Electragician, vastly humbler background. Scientific Instrument Making, Systems Electrician, first almost killed myself inside a valve TV at the age of 7 ... made me the halfwit I am today ... most of my motors have been tiny to small ac & dc, brushed, brushless, VFD, VSD, exotic little constructions of esoteric automagnetic eddies and current shunts and back emf’s and all driving cardiac pacemakers and microscopic escapements inside dear little nipple hung fob watches etc ... nothing like those beautiful big industrial behemoths you gentlemen reminisce all over ... about ... with ... umm ... you know what I mean ...


Where was I ... oh yes, semantics, well said that man. Aah, the black arts of advertising ...


‘Infrared’ cooktops:
Infrared = heat = lots of electrical energy turned into heat energy = lots wasted into the air and vessels etc.
Losses (>): fuel/sunlight > electricity > chemical battery > electricity > inverted to 240VAC > cooker > air/vessel > food.

Induction: same, but less wasted in air/vessels.
Jugs: focussed, short ‘on’ times. Lotsa losses in generation, storage, inversion.
Microwaves: focussed, short ‘on’ times. Lotsa losses in generation, storage, inversion.

Conclusion: gas (or genny if you’re rich)


240 Volt AC domestic ‘inverter’ fridges:
240Volts AC > rectified to 339 Volts DC (240 x 1.414 to get DC equivalent power) > inverted back to AC at varying frequency & shaped voltage > motor (phew!).
Losses (>): Fuel/solar >> battery >> inverted to 240VAC > rectified to DC > inverted to AC (frequency/voltage shaping) > motor (mechanical/hydraulic & cabinet/ambient/front opening losses). Lots of electronics to wear out or go wrong in the inverters and fridges, not designed for unstable or vibration prone environments.

The advantage of ‘inverter’ air cons and fridges (they’re both just heat pumps) is that they can run quite slowly, rather than frequently starting and stopping and only being able to run at full speed or nothing. Their main advantage is that they don’t ‘clunk’ on/off, tend to keep temps steadier (less important in domestic fridges than air cons), and don’t draw huge currents every time they start up. The benefits of their less extreme starting currents are outweighed in vehicular or low voltage DC systems by the very large losses in producing, storing, releasing, inverting, rectifying, inverting and controlling it all.

3-way ‘fridges’: the generally available type are only ‘coolers’ that use thermal evaporation/condensation/expansion techniques to reduce temps to around 20℃ below ambient, therefore not cold enough. Good when used in cool environments. Heat from gas flames or electrical elements is hard to vent away, and adds to heat load inside vehicle/van (which can be good in cooler environments, though need for venting can negate this).

Low voltage DC fridges: designed and built with electrical and cabinet high efficiencies as primary goal, no inverter losses (usually), purpose designed motors. Can use inverter tech, but not common and still don’t have the huge losses of higher voltage gear. Cabinets are usually top opening, which avoids dumping cold air load every time door is opened.

Conclusion: purpose designed low voltage dc fridge (or 240VAC with Oka or trailer full of genny and batteries if you’re not poor)(or learn to enjoy tea again)


(and before you lot jump on my maths and physics; simplification, exaggeration and corner cutting are prerogatives of the old, so go back to calculating tubes of acne cream vs income)

[austastar]

Love it!

Thanks, it will leave a smile on the dial all day.

Cheers

[DeanoH]

Thankyou for that link you provided.

Just before the description of the VVVF drive, you'll see the words, and I'll quote from the article here,

Most commonly, the terms VFD and VSD are interchangeable.:


It is also common to refer to a Koala as a Koala Bear, it doesn't mean that it is correct. :)


Tsk ....tsk Michael, selectively quoting :o

Here's the conclusion of the same article relating to the use of VSD,.VFD, VVF terminology.

So which should I use?


It’s most common for industrial control systems to be AC-powered.
In this case, the three acronyms are interchangeable and all refer to the same thing.
In the case of a DC control system, the correct term is most likely VSD.
Or, in the HVAC or mechanical services industry, AC drives might be referred to as inverters.


Deano :)

[Homestar]

In industry, the terms VSD and VFD are interchangeable. I find that most don't know the difference and most use the term VSD, not VFD in my experience. This is despite the they are talking about AC equipment. Maybe miscommonly quoted yes, but we understand what is being discussed as DC drives are generally highly specialised these days and those talking turkey about such things will be on the same page anyway.

It's like generators - as a Specialist in this field that term amuses me as they are alternators - Generators produce DC, and my customers - and you guys as well when we discuss generators - are talking AC. I assume that when someone is talking about a generator that they mean AC, but they are technically wrong. No point getting a bee in my bonnet though, it won't change what people do.

So the term VSD is perfectly legitimate when talking AC starters in my opinion although maybe not technically correct.

[mike123]

Theres two words you dont see together very often,,
satellite internet and toaster[bigrolf]

Yes I know, the system was added too over time. I needed the internet when I could occasionally work from there and then others wanted a toaster :-(

[DeanoH]

Back on the subject of portable/mobile fridges, I've just replaced my two Engels, one MF35 and one MF17 used as fridge and freezer respectively with an upright. After much deliberation I went for an Everkool 146 litre 2 door. The deciding factor here was 55mm insulation for the fridge and 75mm insulation for the freezer compartment.

From an efficiency viewpoint the upright design will be a minus for losing cold air when opened. I've yet to see a caravan type upright fridge with drawers or fold down doors on the shelves to reduce cool air loss, interesting when you consider my 1980's Philips upright freezer does (did) have fold down plastic doors on each shelf to help efficiency.

On the plus side I'm now running one 'new' compressor (Chinese BD35 clone) instead of two 20 yo compressors and have much better insulation. Too early to tell what the comparable efficiency's are but the doubling of capacity and accessibility is certainly a plus. :)

Deano :)

[nick_e]

It's like generators - as a Specialist in this field that term amuses me as they are alternators - Generators produce DC, and my customers - and you guys as well when we discuss generators - are talking AC. I assume that when someone is talking about a generator that they mean AC, but they are technically wrong. No point getting a bee in my bonnet though, it won't change what people do.
.

I think there is just ambiguity around the terms, and it's not surprising there is confusion.

A (modern) car has an alternator that uses a voltage rectifier to output DC.

A genset uses an alternator that puts out AC at mains voltage but they are marketed as 'generators'. Not sure if this is a throwback from the old days before AC took off or if its just a different, non technical use of the term generator.

Actual generators aren't used that much out of specialised applications these days as far as I am aware. Most common applications have been replaced with either AC alternatives or electronics powered by rectified AC supply.

[Homestar]

I think there is just ambiguity around the terms, and it's not surprising there is confusion.

A (modern) car has an alternator that uses a voltage rectifier to output DC.

A genset uses an alternator that puts out AC at mains voltage but they are marketed as 'generators'. Not sure if this is a throwback from the old days before AC took off or if its just a different, non technical use of the term generator.

Actual generators aren't used that much out of specialised applications these days as far as I am aware. Most common applications have been replaced with either AC alternatives or electronics powered by rectified AC supply.

Yeah, it confuses some of our workshop staff too who aren't used to them when we are talking alternators, some mechanics think we are talking about the battery charging alternator, not the main alternator. Makes it even worse when I clarify that with 'I mean the low voltage alternator' which they again think is the battery charging alternator - which is extra low voltage. 😁😇 I finally have to say 'The main alternator the mains power comes out of'...

[Old Farang]

Actually, it is the word "generator" that causes the confusion. A "generator" is not only a machine that generates electricity, but can be any number of machines that "generate" a product, such as water, gas, etc. Even money is referred to as "generating" an income. [wink11]