Wednesday, 5 September 2018

How immoral harmonics influence the work of motors & Generators

EmerichGenerators and motors are adversely affected by harmonics in the networks to which they are connected.

 Typical effects are:
  1. Increased heating due to iron and copper losses at the harmonic frequencies
  2. Higher audible noise emission as compared with sinusoidal excitation
  3. Harmonic currents in the rotor

The harmonic currents noted above are caused by harmonics in the stator winding, which will produce harmonic currents in the rotor, e.g., 5th- and 7th-order stator harmonics will produce 6th-order rotor harmonics, while 11th- and 13th-order stator harmonics will produce 12th-order rotor harmonics.

These rotor harmonic currents will result in increased rotor heating and pulsating or reduced torque.

It should also be noted that system unbalance (standing unbalance or ground faults), expressed as negative-sequence currents, can also reflect into the rotor as harmonic currents, which add to those noted above.

Generators can also produce harmonics and, in particular, triple harmonics that can circulate through adjacent Wye-grounded transformers when generators are directly connected to a load bus. The use of the Delta-connected generator transformers can control this.

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