I have a DanfossBD50 12 volt refrigeration compressor which is controlled by a variable speed 3 phase controller.
I have been having trouble with the controller with 2 replacements and 2 repairs, is it feasible to consider if an Arduino would be able to replace the controller.
Does anyone have experience with hermetic compressors?
I'm in a big learning curve as it is all new to me but I am looking forward to learning Arduino.
Regards
From a failure cause point of view, having gone through 4 controllers all presumably on the same compressor package, doesn't that suggest something to you other than you have faulty controllers. I'd suggest finding out what's been destroying the standard commercial units before endeavouring to design and build your own.
You can use google to find datasheets:
Is this the model you have ->>
http://www.ra.danfoss.com/TechnicalInfo/Literature/Manuals/06/bd150f_mobile_10-02_cx30f102.pdf
I'll sum it up for ya...
your variable speed 3 phase controller is just an inverter
The compressor is just a regular 240AC compressor with an inverter...
You can remove the inverter you have, add a normal PTC motor starter and connect it to the mains. Or buy an inverter - mind you you don't need anything special - a 500W inverter would be good enough
problem solved! 
I think the unreliability issues comes is environment related....in a power boat, one failure was because of a faulty VSR which shorted , other failures were from a poor repair from a service centre ....a capacitor in the unit was siliconed in place.., that's why I'm in the process of learning about electronics.
The compressor is just a regular 240AC compressor with an inverter...
You can remove the inverter you have, add a normal PTC motor starter and connect it to the mains. Or buy an inverter - mind you you don't need anything special - a 500W inverter would be good enough
Please correct me if I'm wrong but I wasn't aware of 12 volt frequency inverters that i could use in place of the controller that is on now.
Regards
xrayxray:
I have a DanfossBD50 12 volt refrigeration compressor which is controlled by a variable speed 3 phase controller.
According to the data sheet kerimil referred to, it is not a "variable speed 3 phase" anything; it is a single phase 240V AC motor.
I assume you've seen the guts of the thing by now. Can you recognise the existing inverter and the 240VAC supply to the motor? Is there any more to it than that? Is the problem within the inverter, or the 240VAC section?
if you've got the same model as the one I posted your compressor is just an AC compressor + an inverter.
An inverter is a thingy that changes for example 12V to 240AC (mains)
Your compressor isn't three phase nor it needs a three phase controller... read the datasheet it's all there are even wiring diagrams that show it
Compressors of this size and displacement normally use like 150 - 200W max. Also you need to take into consideration the fact that all motors use more power when they start up so let's say you should be fine with mere 400W.
But why buy a 500W inverter when you can have a 1200W unit for just a few $ more (guesstimate a decent 1200W inverter costs around 40$)?
I guess that it would be nice to be able to use a laptop on a boat or somethign like that
Danfoss BD 50 Compressor. 12 volt DC to 24 volt DC, speed can vari from 2500 rpm to 4000 rpm
Electronic control unit - # 101no210
3 pins on the compressor and nothing marked,
Regards.
That's perfectly normal all single phase comressors have 3 pin sticking out of their casing. 1 is live, 2 neutral and the third one is for starting winding on the motor. Normally there are some markings there, for example L,N,S or R,C,S but if there aren't any you can establish that yourself
here is how to establish which is which: (note that first he ohms a 3 phase compressor so what is relevant for you starts at 2:16)
you need a PTC motor starter too - it's a thingy that you attach directly on the pins... you need one that matches your compressor wattage (since yours looks like a fairly standard unit (rated to 130W or so) you should be fine with standard stuff that is used on typical fridges)
the rest is simple -> you attach wires to a PTC motor starter, which definatelly has markings so it's hard to go wrong
Thanks...am just googling PTC motor starters and where I can purchase.
Video was informative too.
Much appreciated,
Regards.
no problem
ohh and check the compressor windings (ohm them just as shown in the video), you should get exactly the same results as he got
if by any chance you don't this means you've got a three phase compressor or that it is broken
damn 
I have found another datasheet that suggests that the model you have is in fact a 3 phase compressor
http://www.ra.danfoss.com/TechnicalInfo/Literature/Manuals/06/Danfoss_bd35k_r600a_12-24vdc_06-2011_dehced100g602.pdf
Resistance of all three windings there is the same that means it is a 3 phase compressor and it needs a 3 phase motor controller
To be honest it might not be practical to build a 3phase controller using arduino (possible but expensive and time consuming). Basically speaking a 3 phase motor controller that you have changes the speed of the motor to match requirements of your refrigeration circuit.
When it is hot/you open the fridge and warm air enters inside the motor's RPM are higher and it draws more power. So essentialy it isn't only a speed controller but it also has a microcontroller that senses how hard the motor has to work to keep stuff cool. Thx to that the fridge uses less electricity than a comparable AC compressor - but the disadvantage is of course the cost of the unit.
You'd have to build a proper 3 phase controller + a fully functional PID controller that governs the RPM of your motor.
So now you are basically left with two practical options:
either you fix the unit you already have or you buy an AC compressor that would suit requirements of your circuit. I guess that the costs of both options might be comparable (given the fact that 12V compressors are much more expensive than normal ones)
All BD compressors are three phase brushless DC motors.
Hi,
What is the part number of your control unit?
I found this for the BD50.
http://files.danfoss.com/technicalinfo/dila/06/bd_compressors_04-2009_pi100a402.pdf
BD are DC compressors, not AC
Tom... 
I have read this topic and can say that there appears to be a bit of confusion amongst the contributors.
The BD series of compressors are 12 V 3 phase motors and the controller generates a 3 phase pwm signal which is of a variable frequency which controls motor speed. Very simple to replicate with an Arduino and then use a simple driver L298 (one per phase ) to drive the compressor . You can even use a simple NTC for temperature control and as temp reaches set point slow compressor down and as temp rises speed it up.I have found an old unit with missing controller and am going to fire it up.