Negative Phase Sequence

Negative phase sequence result in heating the stator.

The negative phase sequence heating follows a normal resistance law and hence is proportional to the square of the current. The heating time constant of the alternator is largely a function of the cooling system used and is expressed by the relationship;

square of the negative sequence current multiplied by time duration and equals a constant 'k' which has a value 3~20 for turbo type machines.

In the case of unbalance load, the stator current has negative sequence component. The flux due to negative sequence components rotates in the direction opposite to the direction of rotor. Thereby heavy currents are produced in the rotor causing rotor damaged by over heating.

- MS

Also, the problem of pulsating torques