help building an inverter system

[max2]

hi,
my name is maxim and i'm a mechnical eng. student from israel.
i'm in the planing stage of an electric a/c for my car (a vw beetle). i want to use a standart sealed compressor (400-500 watt) linked to a tweaked dc-ac convertor, witch will allow me to controll the frequency of the current, in turn allowing me to control the speed of the compressor. this way i plan do build an "invertor" a/c system with some nice features like soft start, climate control etc.

i was told that the inverter a/c systems have a special expantion valves. i'v tryed to search about this subject but didnt find anything usefull.

i need some advise about choosing an expantion valve and constructing the system. and i will gladly exept coments and opinions on the project.
thnx,
maxim.

[The Viking]

I won't say don't waste your time, I'm all for learning and strange projects are normally how you do it.

Normally, an inverter (note: I don't include soft starters here) is used to allow alterations to the compressor's duty. As the capacity varies so will the amount of refrigerant going through the expansion device, therefore electronic expansion valves are used (as they are more flexible than thermostatic ones).

In your application (a car), I doubt that you will have a requirement to alter the duty much, therefore you might get away with a capillary tube or a TEV (which will be cheaper and easier to get hold of)

If you want to know more about electronic expansion valves then most major manufacturers makes them, HERE is a link to Danfoss' website.

All the best....

P.S. In a Beetle, what are you planning to use as evaporator and where are you putting it?

[max2]

i plan to buy the evaporator/radiator from a diferent model. i have a "super beetle" so i have a dash to put the evaporator in, but in the testing stage it will be under the dash.

i hope that 500 watt will be enough for the car. in my room i have a 0.8 HP a/c and it does a grate job.

one of the ideas is to be abel to control the duty therw the frequency, and i belive that it wont work at "full" duty all the time. i have the system pretty mutch figured out. i dont understand how to controll the electronic valve in paralel to the compressor (how do they relate to each othere, or the controll is independent etc.)

once i was told that the "invertor" system needs only a capillary tube because all the controll is done by the compressor.

[goodguy]

A standard hermetically sealed compressor needs to operate at full speed to maintain proper lubrication. They normally use some type of a oil pump or a "flinger" to do the job.
I think a VRV compressor is engineered to maintain proper lubrication. I'm not quite sure how it works but would like to know more on VRV lubrication. Can anyone help?

This might be something to think about, good luck in your project.

[max2]

i thought that the diference between danfoss'/musterflux's 12V variable speed compressors and the standart hermetic one is only in the motor.

[max2]

just went threw the details of the electronic expantion valves,
what does "Capacity (R22)" mean?, the value is given in [kW] and i can't understand it.

[paul_h]

The cooling capacity the valve can achieve using r22 refrigerant.

[DEVIL]

goodguy
i can tel u abaut the lubrication of the Daikin VRV,
VRV II,
made the oil return by making the a cycle every 6 hours, or 3 hours, depending on the worcking hours, of the compressor, and the cycle is made by runing the inverter compressor at a low speed, and then jumping one step up, and back down (one step in the speed)
and that whay made the oil return to the compressor.

VRV III
has a'n oil separator, that is fitted to the compressor outpoot, to not allow the oil to go to the indor unit's, and from that oil separator, has a capilary tube going to the compressor suction, fiding the oil back to the compressor.

sorry for my english

[goodguy]

Thank you to the DEVIL!

[DEVIL]

np goodguy, that is what frend are for