Influence of Negative Phase Sequence Currents on Motors

Influence of Negative Phase Sequence Current on Motors Kanthar P (Nathan) Balanathan DipEE(UK, GradCert(RelEng), PGDipBus&Adm(Finance), CEng. , MIEE, MIE(Aust), CPEng. Negative sequence current, generated due to unbalanced voltage can cause severe heating... More

Influence of Negative Phase Sequence Current on Motors
Kanthar P (Nathan) Balanathan
DipEE(UK, GradCert(RelEng), PGDipBus&Adm(Finance), CEng.
, MIEE, MIE(Aust), CPEng.

Negative sequence current, generated due to unbalanced voltage can cause severe heating of the
motor stator winding due to over loading.
This is a power quality issue.
For large motors in power
stations, the motors are supplied from the unit board and the power quality may not be an issue.

However, for small motors, it would be advantageous to measure the three phase voltages and check
the voltage unbalance factor percentage.
In public consumer / industries negative sequence currents
may be an issue.

Motor burning due to negative sequence could go unnoticed.
Power stations and industries should
monitor the low three phase voltages on buses and check the negative sequence influence.
Negative
sequence current tends to generate an opposing torque and rotate the motor in the opposite direction
similar to a braking to Less