Scroll compressor current

[Scott Buker]

I have a machine condition monitoring system in my plant that can monitor current, vibration, temperature, etc. I'm monitoring current on some 15 hp scroll R404 compressors. The current went up on one of them by 10 to 15%. We changed the compressor to avoid burnout and downtime and the current returned to normal. After 5 weeks is climing again, but with a different waveform. We thought that there may have beeen some acid in the oil, but the test showed none. Any ideas?

[nike123]

Current of motor depend on compression ratio and mechanical efficiency of compressor. If compression ratio is changing then current is also changing.
Monitoring current without relation with compression ratio doesn't tell you much about compressor motor.

On the other hand, regular measuring of compressor motor insulation tells you everything about winding state.

Check this post. (http://www.refrigeration-engineer.com/forums/showpost.php?p=94054&postcount=1)

[mad fridgie]

Hi, is this a common system, more than one compressor?
Possible inbalance in oil return. Oil levels in scroll seem to be more critical. (in my opinion) slight loss indicated, increase in current, no sure how the bearings are fed in these machines.