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Old 17-08-2018, 14:58   #181
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Re: Who provides the best 12 volt refrigeration systems?

BLDCMs are quite similar to stepper motors too, and don't need full bridge drivers (though they work better with them). In that, the DC is just sequenced, and therefore is a DC motor rather than converted to approximate AC. The older style, commutated motor is the same, except the sequencing is done mechanically rather than electronically.
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Old 17-08-2018, 15:15   #182
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Re: Who provides the best 12 volt refrigeration systems?

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Do you mean a BLDC moter driven fridge, or generally ? BLDCMs are used in drones, model (fixed-wing) aeroplanes, cars, and in reverse, with a permanent magnet, wind generators though, then, the same device becomes a PMA. There are two styles, inrunners and outrunners. In inrunners, the rotor is inside the stator.

I'm "mostly" talking about Danfoss's BD compressor motors.


Don't know about the other applications you mentioned. But way back in the day's, my electric R/C aircraft had brushed, DC motors. But that was many decades ago, so I suspect many improvements have been made since then.


FWIW, my KISS windgenerator is a permanent magnet, 3 phase, AC alternator (generator).
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Old 17-08-2018, 15:26   #183
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Re: Who provides the best 12 volt refrigeration systems?

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BLDCMs are quite similar to stepper motors too, and don't need full bridge drivers (though they work better with them). In that, the DC is just sequenced, and therefore is a DC motor rather than converted to approximate AC. The older style, commutated motor is the same, except the sequencing is done mechanically rather than electronically.

As Bill Clinton said, "it depends on what you definition of "is", is".


The Danfoss module outputs a modified half wave (wrong term, but the only one I can think of right now). And yes, by all practical definitions, being it always stays positive (or negitive), you could call it DC.


But most are taught that it is AC.


Really depends on which side of the argument you decide to side with.


Now that I know your point of view, I have no disagreements.
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Old 17-08-2018, 15:47   #184
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Re: Who provides the best 12 volt refrigeration systems?

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I'm "mostly" talking about Danfoss's BD compressor motors.


Don't know about the other applications you mentioned. But way back in the day's, my electric R/C aircraft had brushed, DC motors. But that was many decades ago, so I suspect many improvements have been made since then.


FWIW, my KISS windgenerator is a permanent magnet, 3 phase, AC alternator (generator).

That is exactly the construction of an inrunner BLDC motor, though the motors have a far higher short term power density. In single sided operation, you can wire the motor in star configuration, then just sequence a positive voltage around the discrete terminals. OR, you can treat it as a 3-phase motor, and put a full bridge driver on each terminal
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Old 17-08-2018, 16:08   #185
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Re: Who provides the best 12 volt refrigeration systems?

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That is exactly the construction of an inrunner BLDC motor, though the motors have a far higher short term power density. In single sided operation, you can wire the motor in star configuration, then just sequence a positive voltage around the discrete terminals. OR, you can treat it as a 3-phase motor, and put a full bridge driver on each terminal

The original rectifier box was wired per your first example.


I have no idea how the new rectifier/regulator box, is internally designed.


Good discussion!
Thanks
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Old 17-08-2018, 16:12   #186
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Re: Who provides the best 12 volt refrigeration systems?

Now the biggest question which is better txv or cap tube with a holding plate system freezer with spill over fridge?
Personal experiences please.
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Old 17-08-2018, 16:24   #187
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Re: Who provides the best 12 volt refrigeration systems?

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The original rectifier box was wired per your first example.


I have no idea how the new rectifier/regulator box, is internally designed.


Good discussion!
Thanks

I have two 2.5kW alternators that are wired delta, to the 3-phase rectifier. Note to all. If you want to charge two sets of batteries, the best way by far is to have two external rectifiers, though one of them can just be a half-bridge one, the positive half but make sure that the full bridge one can handle the full output of the alternator. Plain diode splitters won't fully charge either battery, relay types, in my experience, are prone to corrosion and failure. Me, electronics engineer for 40 years.
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Old 17-08-2018, 16:51   #188
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Re: Who provides the best 12 volt refrigeration systems?

I would not know where to start figuring out how to implement that. Suggest any 101 howto's, sourcing links, books to read?

These are pretty bulletproof ​ https://www.bluesea.com/products/762..._-_12V_DC_500A
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Old 17-08-2018, 17:03   #189
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Who provides the best 12 volt refrigeration systems?

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Now the biggest question which is better txv or cap tube with a holding plate system freezer with spill over fridge?
Personal experiences please.


I am not trying to be a smart butt, but what do you mean by better?
Itís my belief that a TXV allows greater flexibility if you will and throttles the compressor as demand changes, it by its design is more flexible, reacts better when you toss in a case of beer or big watermelon or gallon of ice tea to cool down.
It is also less likely to clog, however as Pete pointed out it you have a good filter, clogging isnít an issue, any particle that can clog, is filtered out.
I believe a TXV is more efficient and my belief is driven partly due to the fact that now that home HVAC systems have to be a min of 13 SEER, you have seen TXVís become almost universal on home HVAC systems.

However as anyone will tell you, a system is more than the sum of its parts, a poorly designed as in components donít match well with a TXV will almost certainly perform worse and use more power that a properly matched cap tube system.
These things are a lot like people who ďbuildĒ computers. They donít build everything, they take parts manufactured by others and assemble them, if they do it correctly and have a Mother board that is matched to the CPU, correct amount and type of memory, Video card that matches the use etc, etc then you have a great computer.
But you can take quality brand name components that donít play well together and even though you have all the right parts, itís a piece of junk.
You can have a very efficient cap tube system and it be in a cold plate, and you can have a very efficient evaporator system also.
Biggest thing that I believe Richard has been trying to get people to understand is that there is NO inherent efficiency increase with a cold plate, it doesnít make energy on its own, it is merely a storage medium, and that in a system in stasis, it is no more or less efficient than a regular evaporator, however if you have periods of excess energy like excess Solar, one good way to take advantage of this excess is by storing energy in a cold plate to be used later when your energy poor. You can of course do the same with a bigger battery bank.
I would argue that in stasis, with all the variables being equal that a cold plate is less efficient, reason is you have to first cool the fluid in the plate, then it cools the box, a evaporator cools the box directly. However we do open the door and take cold things out and out warm things in.

A good quality system is going to beat a poor quality system, regardless of the type of parts used.

If a manufacturer can be in control of everything, box size, insulation value etc., well then they can very finitely design a system just right for those conditions, and in this case you almost always see cap tubes. Think nearly and box fridge you can buy.


Not many of us have likely had both a quality cold plate system and a quality evaporator system.
I had an AB super cold machine, great little system really, but it was in a box that was way more than it could Cool, so it performed like crap.
Not its fault, someone was asking a boy to do a manís job and it couldnít.
It would not cool my box, not at all. I gave it to another cruiser who installed it in their much smaller box and itís performing great, he is real happy with it.
So even a good system if itís not matched to the box, you wonít be happy.
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Old 17-08-2018, 17:06   #190
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Re: Who provides the best 12 volt refrigeration systems?

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there is NO inherent efficiency increase with a cold plate, it doesnít make energy on its own, it is merely a storage medium, and that in a system in stasis, it is no more or less efficient than a regular evaporator, however if you have periods of excess energy like excess Solar, one good way to take advantage of this excess is by storing energy in a cold plate to be used later when your energy poor.
Reducing the number of startups per 24hrs is another factor, not minor IMO.
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Old 17-08-2018, 17:20   #191
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Re: Who provides the best 12 volt refrigeration systems?

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Reducing the number of startups per 24hrs is another factor, not minor IMO.


True, but a properly sized compressor with on and off set points set decently far enough apart, doesnít cycle excessively either. You get excessive cycling when you have a thermostat that comes on and off 1 degree apart, but if itís five degrees apart and it takes four hours to drop those five degrees, well then you donít cycle often.

However take that system and throw in a whole bunch of warm food and or fish to freeze, well then itís going to literally take all day and night to return to set point temp, and itís likely to get warmer than you want too.
That is when a TXV shows itís worth, it can open up allowing more refrigerant to flow cause the plate is warmer and can take more refrigerant, this loads the compressor and you see it draw more power, but it will recover faster.

There are other ways to skin that Cat remember, you could have a BIG compressor that freezes a plate down in a hurry and is a cap tube, then stays off for long periods of time, throw in a big heat load and it reacts by shortening its off periods. Different theory of operation, similar result.


All, good quality systems, are good quality systems. I think Iíd pick a system that I was comfortable with the service and support after the sale. I think I would pick the manufacturer, not the system so much?
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Old 17-08-2018, 17:20   #192
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Re: Who provides the best 12 volt refrigeration systems?

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I am not trying to be a smart butt, but what do you mean by better?
Itís my belief that a TXV allows greater flexibility if you will and throttles the compressor as demand changes, it by its design is more flexible, reacts better when you toss in a case of beer or big watermelon or gallon of ice tea to cool down.
It is also less likely to clog, however as Pete pointed out it you have a good filter, clogging isnít an issue, any particle that can clog, is filtered out.
so for the flexibility and load compensation a txv system would from that standpoint be preferred.
Now I will always have excess power generation so a holding plate system makes the most sense from that standpoint.
I want to be able to quickly freeze that tuna or salmon I just caught . ( the amounts I won't be able to eat in a couple days. )
so it seems a txv may be the better option then .
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Old 17-08-2018, 17:55   #193
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Re: Who provides the best 12 volt refrigeration systems?

It is for me.
But like I said I believe you can do very similar with a cap tube system and an oversized if you will compressor, especially if itís freezing down a cold plate, and especially if that plate is actually going though a phase change.
Similar results, very different way of achieving them, but I think it would work, just as well or maybe better depending on conditions.

Now Iím a believer in having excess cooling capacity, that way your always happy, if your perfectly sized, then every time you do something out of the design parameters, like go to the grocery store and buy a bunch of food to freeze and refrigerate, then your not happy.
Or travel to where the water is 90F.
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Old 17-08-2018, 17:58   #194
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Re: Who provides the best 12 volt refrigeration systems?

That is the other advantage of holding plate, able to oversize everything for that kind of scenario, will have a lot of "immediately available" energy-absorption capacity to prevent big warm loads from defrosting the existing contents as much.

The evaporator system will take longer to recover.

Right?
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Old 17-08-2018, 18:01   #195
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Re: Who provides the best 12 volt refrigeration systems?

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That is the other advantage of holding plate, able to oversize everything for that kind of scenario, will have a lot of "immediately available" energy-absorption capacity to prevent big warm loads from defrosting the existing contents as much.

The evaporator system will take longer to recover.

Right?
that is correct .
My only decision would be cap tube or txv. For my holding plate system
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