the function of the electronic expansion valve

[Crystal-426]

Hello, everyone,
Who can supply the file of the electronic expansion valve such as:modulating magnetic valve, stepper motor valve, and pulse-width-modulated valve to me ? It is better including the priciple, the configuration and the appilication and so on.
Because recently I am collecting the valves for refrigerant flow control. But the information of the electronic expansion valve is very old and little in the book of the refrence which I have found now.

thank you very much !:)

Crystal

[750 Valve]

its amazing what "googleing" something will return - try it one day.

Danfoss have some tech data on their sites, Alco and Sporlan also make stepper valves

http://www.danfoss.com/North_America/BusinessAreas/Refrigeration+and+Air+Conditioning/Literature/Documentation+UK.htm

PWM (pulse width modulation) basically is assigning a time frame (in most refrigerant controllers it is 6 seconds as default) - if a valve was to require a percentage of 100% then the solenoid would keep the valve open for 6 seconds - 100% of the assigned time, then another 6 second timeframe will begin and the valve percentage required re-assessed by the control system. If a valve percentege of 50% is required the valve would remain energised for only 3 seconds of the 6 second timeframe - it would spend the other 3 seconds de energised and not flowing refrigerant. A 25% valve percentage would equate to 1.5 seconds of opening tima and 4.5 seconds shut off.

The valves used are direct acting (the solenoids pull a plunger off its seat) and an interchangeable orifice is used to provide differing valve capacities

[star882]

Hello, everyone,
Who can supply the file of the electronic expansion valve such as:modulating magnetic valve, stepper motor valve, and pulse-width-modulated valve to me ? It is better including the priciple, the configuration and the appilication and so on.
Because recently I am collecting the valves for refrigerant flow control. But the information of the electronic expansion valve is very old and little in the book of the refrence which I have found now.

thank you very much !:)

Crystal

A modulating magnetic valve, also known as a "voice coil" expansion valve from the resemblance to a speaker coil, uses a linear motor to apply a force to the valve needle which is proportional to the current flowing through it. It needs an elaborate control system to regulate flow as the flow is dependent on position while the linear motor controls force.

I don't know too much about stepper motor valves but I think it's almost exactly the same as the modulating magnetic valve but with a stepper motor instead of a voice coil. It does not require as elaborate a control system as the position of a stepper motor is directly controlled, but it cannot adjust as fast.

There's also a piezoelectric expansion valve in development that aims to be simple to control (position proportional to voltage), use practically no power except when changing position, be able to adjust quickly, and be mechanically simple. It looks very promising and I think it might become the expansion valve of choice for HVAC. The valve itself operates at high voltages (up to 200v or more depending on the valve) but that high voltage is generated from the low voltage supply using a small flyback transformer as it is the simplest and cheapest way to make a variable high voltage power supply under digital control.

EDIT: I found out that some of the prototype valves they're working with require as much as 800v of drive voltage!

The PWM solenoid valve is the simplest. All it is is a solenoid valve with a very small bore. The controller simply switches power on and off to control it. It requires careful system design to avoid problems caused by vibrations.

[Brian_UK]

its amazing what "googleing" something will return - try it one day..........
A very fair comment 750 (I get tempted with that answer myself :eek:), but I seem to remember that China does not allow Google to operate in their country.

Or if it does then only on a limited basis.

It's a pain but I suppose that we must grin and bear it a little ;)

[Crystal-426]

To 750 and star:
thank you very much! now I have known a little about the EEV(including the types of three valves respectivly) . thank you!
Can you supply some pic. of the configuration or other site links?

Best wishes

Crystal

[Crystal-426]

to Brian:
I think you don't kown more about the China. In my country, we allow Google to operate in our country and we usually line on it. Because I hav't search the thing which I need it , I think if we help each other, all of us will gain the best achievement.

Crystal

[750 Valve]

A very fair comment 750 (I get tempted with that answer myself :eek:), but I seem to remember that China does not allow Google to operate in their country.

Or if it does then only on a limited basis.

It's a pain but I suppose that we must grin and bear it a little ;)

Yeah Brian I know what you mean mate, sometimes I'm stuck between a rock and a hard place - I want to help but the best help is "self help" - this is the one you will remember the longest and seemed to be the basis for my entire apprenticeship. Nothing can help you if you won't help yourself. :D

[Brian_UK]

to Brian:
I think you don't kown more about the China. In my country, we allow Google to operate in our country and we usually line on it. Because I hav't search the thing which I need it , I think if we help each other, all of us will gain the best achievement.

CrystalThat's good Crystal, we all go by what we read in the newspapers - and they are not always true ;)

[nike123]

to Brian:
I think you don't kown more about the China. In my country, we allow Google to operate in our country and we usually line on it. Because I hav't search the thing which I need it , I think if we help each other, all of us will gain the best achievement.

Crystal
http://news.bbc.co.uk/1/hi/technology/4645596.stm
http://cyber.law.harvard.edu/filtering/china/google-replacements/

You could always use proxies for accessing sites that are blocked by your ISP!

[surendrank]

Hi.. guys, here is few pictures of dismantled EEV.

suren..:):)

[surendrank]

Sorry, pictures were not uploaded in my first attempt.

suren..:confused: