Air compressor with softstarter?

[mobex]

It is adviseble to equip Air Compressor (37KW) with direct start with softstarter? The reason it would be that the presosate stops and starts the motor many times.

 

[jraef]

It is done all the time. I have never seen it be a problem.

 

[DickDV]

One word of caution. If it is a piston type compressor, you will not get a big improvement in softstarting because the motor has to develop enough torque to get past the first compression stroke. For other styles, it is simple and the results are good.

 

[itsmoked]

Yes but doesn't the slower speed present a lower torque requirement? (once above the initial compression stroke torque need is met.)

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[mobex]

The compressor is Sullair LS-12-50H single stage rotary screw. So it is posibble in this case?

 

[itsmoked]

Bingo! That will work well.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[Skogsgurra]

Yes. And if you use a VFD instead of a softstarter, you can usually program it to run on demand and with optimal efficience instead of switching on/off.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[itsmoked]

VFD? I don't remember if those type compressors are dependant on some minimum speed to maintain sealing?

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[ozmosis]

Just a simple tip. Reduce leakage first before applying any additional control. Fitting a Softstart will invariably improve matters but if the compressor is continually on/off then a simple and (most) effective method of saving energy is to reduce leakage.
I have seen many a very expensive control system introduced into air-compressor systems and all they do, if leakage is not investigated first, is to compensate for the leaks.
Do that first then introduce control strategies.

 

[Skogsgurra]

Yes, smoked. The rotors don't touch - there is a groove and a ridge to prevent leakage between the male and female profiles. And that kind of seal is less effective at lower speeds. But a smart girl/guy makes the inverter switch off when speed approaches "leakage speed".

There are quite a few compressors using this technique. One of them carries a large Greek "eta" to indicate high efficiency.

Gunnar Englund

http://www.gke.org

--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[itsmoked]

Skogs; I had a see-thru working model of a Roots type blower but have never actually seen the innards of a screw compressor.

Thanks for the info.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[Compositepro]

One important point that hasn't been noted is that almost all compressors are started unloaded. The outlet of the compressor is vented to atmosphere (or back to the inlet) in order to significantly reduce the torque required to start it.

 

[jraef]

Just a point of order; the OP never said a word about energy savings... Sometimes a compressor is just a compressor.

Mobex,
I used to be the supplier of all soft starters for Sullair years ago, I assure you there is no problem with soft starting them. In fact some of the dealers insisted on supplying soft starters even if the user didn't ask for it because they got fewer call backs for mechanical problems.

Keith,
I've got a small plastic see-through model of a Sullair compressor. If you spin it fast enough with your fingers, you can feel it moving air. If I remember to, I'll bring it by some time.

 

[itsmoked]

Cool jraef! Wish I knew what happened to my Roots demonstrator. I'd never throw it away, but I haven't seen it in years.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[jraef]

I've never seen a model of a Roots blower, but I've seen he real things and I'm willing to bet that the clear plastic model I have is the same as yours, just with a green color scheme and a different name emblazoned on the side . When I find where I put mine, I'll post a picture of it.