Scroll compressor and VSD

[ozmosis]

I'm looking for some detailed information on the combination of scroll compressors with a VSD (VFD if you're in the US). More specifically I'm trying to find typical efficiency/performance curves that highlight the benefits (if any, but I'm pretty sure there are) of using a VSD on a scroll compressor.
Anybody know of any? I've tried googling but cannot seem to get to any specifc such as this.

 

[Skogsgurra]

sed2developer,

I know that your (former?) parent company delivers drives for the Atlas-Copco screw compressors and that there is energy optmisation built into the parameter sets. It seems to take everything into account like always working at the optimum operating point with regard to motor and compressor efficiency dependent on speed, air temperature, tank pressure setpoint - everything.

The guys in Belgium - probably Bruxelles - should know a great deal about this. They deliver the complete units, with Master Drives and optimisation.

 

[ozmosis]

skogsgurra
still the parent company (you can run but you cannot hide.)
I'm familiar with the A-Copco screw compressor and the systems supplied to them but I think (though I'm no expert) that the performance of the scroll compressor is quite different. Certainly when we are starting (off load)and then running, the characteristics are near variable torque in performance. The relationship between frequency and the cooling capacity seems linear but again, I'm not sure. The two main companies, Maneurop(Danfoss) and Copeland(Emerson) are not too forthcoming in providing info to us.

 

[Skogsgurra]

Sorry, I didn't realise the rather big difference between scroll and screw. I had a quick look at the Copeland site and I can see that the scroll works very differently. probably no use talking to the screw people then.

 

[ClydeMule]

What kind of information are you looking for?

You won't find any information from Copeland because they won't couple a VFD and Compressor, or warranty a compressor if you do it yourself. Maneurop only does it for really little compressors like 1/8 ton or something like that.

Because the Copeland scroll is compliant ( the scroll flanks are held together by centrifugal force), when you slow the thing down to 40Hz or less, the flanks separate. That 40HZ is also variable depending on the compressin ratio. This is from a Copeland app. engineer.

I don't know what danfoss has done.

Copeland's technology for variable capacity is based on unloading the compressor. They acutally move the orbiting scroll up a few thousanths to relieve the discharge pressure. You can go down to 10% @ constant speed. It is actually pretty simple, there fore reliable. They only make this up to 6 HP though. I have been told they are working on a horizontal, double ended, unloading scroll that is something like 30 HP. They call it the DIGITAL scroll. Check it out on their website. I have built a couple of small chillers using this. The first one we made held the chilled water temp @ +/- 0.05 F at only 30% load.

For variable speed compressors, you will have to look at asia. Daikin, Sanyo, Mitsubishi, LG, and Bright (china), have INVERTER scroll systems. Mostly on mini splits.

I could share more, but you should explain what you are after.

Regards,

Clyde

 

[HVAC68]

There are many companies like Daikin, LG, General, Toshiba Carrier who deal with VRV systems using Inverter driven scroll compressors.

HVAC68