Frequrency conversation technology & a normal rotatory compressor

[ernestlin]

Dear Advanced sirs:
If frequrency conversation technology can be applied to a normal rotatory compressor?Is that possible? If it's feasibility, please tell me what it should be considerated? Thanks a lot for any input!

[NoNickName]

I assume that by "frequency conversation" you mean "variable frequency driven" compressors.
The short answer is yes, though you have to contact your compressor manufacturer for checking the operation envelope and limits.

[ernestlin]

Thanks, Nonickman. If a normal rotatory compressor work under a lower frequency, is there any negative influnence on the oil supply?? As I know, the oil is supplied by a centrifugal oil pump in hermetic compressor, and the pump is driven by the motor.

rgds
Ernest

[NoNickName]

Yes, there is a negative influence on oil return. I normally set my inverters to run at full speed for 30s every 10 minutes to ensure oil return.

[nebbie67]

There's a lot of variables to discuss to, in order to establish minimum rotation speed. First of all, if you talk about an hermetic or semi-hermetic compressor, you must consider minimum flow of refrigerant in the suction necesary to cool down electr motor windings, and if the windings are wrapped to support an VFD use (wires insulation). And, over this, don't forget problems regarding harmonics distorsions on the electrical lines that usually an inverter can generate.
It seems not so simple, isnt'it ???

[ernestlin]

Yeah, very detailed suggestion, thanks! nebbie. I totally agree with your opinions, and will consider them throughly. It's really a complex problem, so the various experiments may help me slove it. : >

[Electrocoolman]

Another point is that the compressor needs to be 3 phase type. Speed control cannot work on 1 phase compressor, though you can get a VSD for single phase supply.

[NoNickName]

The unit can be designed with single phase supply and single phase inverter, but then internally three phase will run between the inverter and compressor.