ATLAS COPCO Voltage

Dear friend pls check your system voltage. New motor Resistance and inductance value chaeck with help of motor checker it should be ballance . pls sure that is there any D.C load or VFD connect same source . kindly give exact vale of system voltage , motor resistance , system harmonics . pls check Motor no load current . pls give result back all the best

The imbalance is less than 5% and that might not be such a huge problem (except some additional heating due to the slightly more pronounced negative sequence current. However, (a) are the line currents balanced in de-coupled condition? (b) what is the % imbalance when partly loaded? (c) is your system voltage fully balanced? (d) Does the compressor have a dynamically balanced fly wheel?

On receipt of your response, we should be able to look at the issue with more clarity..

Tilak Ghoshal

Dear All,

Thanx for ur inputs. I have checked that motor in de-coupled position. The motor shows slight imbalance of current which is 192A in one phase and 212 A in other phases. We also checked the motor resistance and it was equal in every coil. The voltages are balanced.Kindly suggest more towards solution.

Best Regards,

AA

As you can see, the variation in the NLC itself is more than 10%........motor winding resistance is so small, it will not tell you much either. What you need to check for really is the 'inductance' and there are instruments available for it. Also, have a look at the rotor for any cracks/partial discontinuities etc in the shorting bars (I assume it's a cage rotor). And above all, if the imbalance problem is being observed after the last rewinding, it might be worth having it completely re-wound afresh by a competent winder.

Tilak Ghoshal