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View Full Version : VRF/VRV exact compressor motor and power type







amat_24
03-11-2014, 08:09 AM
Good day everyone.

I'm currently in the process of exploring the VRF technology in preparation for working in VRF sales
(my background in in water chillers).

I've done some reading and questioning here and there, and been able to learn alot
However, there has been a topic regarding the VRF that no one has given me a clear answer to. Not the internet, not the product manuals, and certainly not the engineers already working in the VRF business. And I was hoping that someone here would be kind enough to explain this to me:

Is the compressor motor type AC or DC????

Now, I know that all VRF manufacturers market their product as "DC inverter compressor" based
But isn't an inverter a device that converts DC to AC (PWM, but still perceived as AC)? Doesn't this make the motor itself AC, and the DC is merely used to produce AC of controllable frequency (and therefore controllable motor speed).

I took a look at a power wiring diagram of a VRF module and it looked exactly like this:
3-ph power -> 3-ph bridge rectifier -> (now DC power) -> capacitor and inductor to smoothen the ripple -> Inverter module (IGBT's) -> Motor (3 wires)

This looked to me exactly like the VSD/VFD configuration

Does this mean that the "DC inverter compressor" is pretty much just a compressor driven by an AC motor thats modulated by a VSD?
If so, why don't they market it as VSD? (technically correct term, already well known in the market)

Also, I recall reading somewhere that the VRF compressors include a permanent magnet, which means that they are NOT induction motors.

If this is true, then what kind of motors are they?????

The same applies to condenser fans. The manuals claim that they are DC to enable speed control, but are they?


Looking forward to your help! :o

Brian_UK
03-11-2014, 01:29 PM
Hi Amat and welcome to the forum.

Hopefully this link will help explain the operation for you.

http://www.airconditioning-systems.com/dc-inverter.html

Also, yes they do use DC fan motors, Daikin motors run at 325vdc if I remember correctly.

amat_24
04-11-2014, 12:20 PM
Hi Amat and welcome to the forum.

Hopefully this link will help explain the operation for you.

http://www.airconditioning-systems.com/dc-inverter.html

Also, yes they do use DC fan motors, Daikin motors run at 325vdc if I remember correctly.


Thanks for the warm welcom Brian! I'm glad that I can be a part of this community of refrigeration and cooling professionals, and hope to learn a lot from you :)

Your link pretty much sums it all up...
apparently the motor IS DC, however, the brushless DC motor's working principle in similar to that of an AC motor, in the fact that alternating the current between the poles is done by electronic means (inverter) instead of the traditional "brush" in typical DC motors.

Thanks again mate! you've saved me a lot of headache.
Searching for info on the VRF on the web directed me to promotional info, not scientific stuff on the working principle.