unbalance current

[mre212]

Dear Sirs,

Is it normal to measure current on Motor grounding cable IF no can this cause unbalance current.
Please be informed we have two motor one by inverter and the other one by soft-starter and they have the same problem (unbalance current)
grounding system TNC

looking forward to read from you
Thank you

[mbc]

Hi
Unbalanceing current can be from .

Unequal of voltage
Unequal of ohm's in Electromotor
Leak or damaging wiring in electromotor
Loose wire in connection box or wiring system
Test electromotore with megger and leak of that

Don't worry for
2 of 3 percent unbalancing with equal voltage .

[mre212]

thank you mbc
the current unbalance more than 10% and nothing from the above

[mbc]

Hi
Also if you have broken conduction on ROTORS Your current always move and come down and goes up .

[mre212]

this is an ammonia plant with two stage each stage with separate electrical panel but both of them supply from same transformer the current unbalance occur only in one stage and we notice this unbalance for all the motor compressors and pumps

[redroge]

Check your voltages phase to phase not phase to earth or neutral sounds like could be low voltage on supply voltage

[mre212]

The source voltage phase to phase as following:
V1=380.1 v
V2=383.2 v
V3=377.9 v

The load voltage phase to phase as following:
V1=372.1 v
V2=380.3 v
V3=374.3 v

The source power feeds the load through 6 single core 300mm2

[Grizzly]

Erm!
Sorry for being silly!
But What exactly is your problem with the plant?
Only that's not 10% error
Does your plant not operate properly or are you just worried about what you are seeing\/

[Glenn Moore]

The way invertors are grounded can cause many problems . Also the type of invertor can cause current issues. The size of the earth bonding cable and its route from the motor to the invertor etc all can cause problems . Is the invertor sensing a current problem and alarming or is this just an observation
What are the current readings at the motor terminals as the safeties in the invertor and the soft starter should detect any problem and log any errorp

[mre212]

The two screw compressors driven by the same invertor type SINAMICS G130 one of them has current unbalance and the other no
please see attached motors readings
cp1 Percentage Imbalance: 9.3% (invertor )
cp2 Percentage Imbalance: 14.1% (Soft starter)
cp3 Percentage Imbalance: 2.3% (invertor)
cp4 Percentage Imbalance: 2.2% (Soft starter)

cp1 and cp2 MP, also the pump connected to this panel has current unbalance
cp3 and cp4 LP

[nike123]

Inverter powered motors and soft starters always have current on motor grounding cable because of inverter filtering circuit.
What I would suggest is call energy distribution company specialist to check distribution panel and cables since unbalance is common factor on one distribution panel.

[mre212]

we are still troubleshooting and i am sure you will help me gentlemen and now are thinking of the electro- magnetic fields which generated by single core cables but we are wondering why only this panel, the other one ok and they are from the same transformer the same main distribution panel

Thank you