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07-10-2010, 03:04 PM #1
EXV and Compressor Variable speed drive
Hi,
can someone please explain on how EXV and Compressor VSD work together? Will EXV send signals to the compressor VSD to regulate the flow rate?
please advice.
Thanks
-jp
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15-10-2010, 03:02 PM #2
Re: EXV and Compressor Variable speed drive
Hi JP,
From my experience, the required cooling load will be worked out by the main control unit for the chiller/refrigeration machine, from the leaving water/air temperature and the time it took to reduce the temperature.
The control unit will then send a signal to both the compressor and EXV to regulate the refrigerant flow and pressure difference to match the required cooling capacity; if possible.
I hope this helps, though it is a bit vague. I have done a lot of work with Turbocor units, and they generally work on this principle.
Thanks,
Bash
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17-10-2010, 01:30 PM #3
Re: EXV and Compressor Variable speed drive
The vsd needs a signal to change the frequency of vsd . The signal is either from a pressure transducer mounted on the casing of compressor . In other words, the suction pressure change due to fall in load is sensed by pressure transducer & it is converted in a 4 to 20 milliamp signal .the signal changes the frequency & hence the speed .
You can install a temperature transmitter to achieve the frequency change .the exv will respond on the pressure differential across it`s port
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17-10-2010, 03:04 PM #4
Re: EXV and Compressor Variable speed drive
EXV and VSD do not necessarily know what they are doing one another. They are on different control loops. EXV is regulated on superheating, VSD on heat load.