Inverter fridges

Inverter fridges have a compressor which can run at different speeds, unlike the constant speed compressor of older fridges. They're usually mains-powered. I'm not aware of any 12v versions.
 
pvb said:
Inverter fridges have a compressor which can run at different speeds, unlike the constant speed compressor of older fridges. They're usually mains-powered. I'm not aware of any 12v versions.
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There is a range of compressors made by Danfoss specifically for mobile use in 12vdc, 24vdc and various refrigerants. I'm sure there are other brands too
 
Rum Run said:
There is a range of compressors made by Danfoss specifically for mobile use in 12vdc, 24vdc and various refrigerants. I'm sure there are other brands too
Click to expand...

Yes, but these are single-speed on/off compressors, not the variable speed compressors which are a feature of inverter fridges.
 
BD1.4F-VSD (Variable Speed Drive) 12-24v
The new BD1.4F-VSD from Secop compressors produced for Danfoss is 60% smaller than previous models and weighs in at only 2.3 kilos. Perfect for 10-20 litre in car/ van/boat cabinets or portable boxes that need to fit into tight spaces without compromising storage space.
 
Isotherm Compact units use variable speed Danfoss compressors (e.g. BD35F). Isotherm even has a "smart" controller that takes advantage of this.
 
pcatterall said:
I was thinking that the inverter fridges alter the incoming AC to DC and that there could be an opportunity to bypass the AC bit and simply supply DC power from batteries !!
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They probably do exactly that, but the intermediate voltage may not be suitable for feeding from boat batteries.
 
I know of an inverter fridge on a boat and if not on shore power it has to run from guess what, an inverter, so any power saving is just moved to inverter inefficiencies.
I think it was cheaper than a 12v dc fridge though.
The extra controller for the danfoss units do run the compressor at lower speeds and run colder when on charge volts to store cold in the food so it can run less when the volts drop.
 
Technically the 12VDC compressor fridges are inverter fridges anyway, as the compressors have AC motors in them and the electronics block does the inverting (conversion from DC to AC). Variable speed is then pretty trivial and depends on if the manufacturer has bothered to build it into the electronics.
This is quite different from domestic fridges that usually run directly from mains power with fixed frequency (the speed of an AC motor is more-or-less tied to the AC frequency). If a manufacturer wishes to achieve variable speed in a domestic fridge compressor (supposedly this has some advantages, otherwise why do it), there's not much alternatives to rectifying the mains to DC and then inverting it back to (variable frequency) AC. This is commonly done for controlling the speed of industrial AC motors in e.g. lathes, etc. Sometimes they are called VFD (for Variable Frequency Drive) Inverters.
 
trbt said:
Technically the 12VDC compressor fridges are inverter fridges anyway, as the compressors have AC motors in them and the electronics block does the inverting (conversion from DC to AC). Variable speed is then pretty trivial and depends on if the manufacturer has bothered to build it into the electronics.
This is quite different from domestic fridges that usually run directly from mains power with fixed frequency (the speed of an AC motor is more-or-less tied to the AC frequency). If a manufacturer wishes to achieve variable speed in a domestic fridge compressor (supposedly this has some advantages, otherwise why do it), there's not much alternatives to rectifying the mains to DC and then inverting it back to (variable frequency) AC. This is commonly done for controlling the speed of industrial AC motors in e.g. lathes, etc. Sometimes they are called VFD (for Variable Frequency Drive) Inverters.
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Ahh, thanks! I had been hoping that somehow there would be the possibility of using batteries at the DC operational phase which would then be inverted back to AC. I even envisaged that a fridge could be dual voltage ie normal inverter AC for when on mains and switchable to Batteries when sailing. Ah well ......dream on !!
 
These compressors are brushless DC motors and very efficient as they also match the speed to the demand thus keeping consumption as low as possible. They are not the same as the domestic AC machines, although both pump refrigerant these are designed for the application, both will work however in terms of efficiency the BD low voltage machines will win hands down on efficiency and noise. We do a lot of work in this field in the commercial world which is just scaled up technology.

https://assets.danfoss.com/documents/86063/AI211686422592en-000701.pdf
 
Sure, but the "motor" part (sans electronics) in "brushless DC motor" is basically no different from a 3-phase synchronous AC motor :)
A BLDC controller is a bit more sophisticated than a simple inverter, but the general principle is the same.
The efficiency and low noise comes from the variable speed and that's all in the electronics either way.
 
Yes similar I agree, thus being wound as three phase and not having a start winding will make it more efficient than a domestic fridge 240v and 12/240v inverter even before we consider the speed control v fridge temp optimisation
 
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