Reducing Harmonic Effect

Note:

During operation with overmodulated space vector modulation, the harmonic contents in the output current are

increased. The drive can then be heated up more strongly.

However, if you are talking about the effects of harmonicvs on the plant, then the issue is different:

Frequency converters generate the high-frequency noise currents which have already been described. In addition, low-frequency harmonics should be taken into account. As a result of rectification of the line supply, a non-sinusoidal line current is drawn which causes a distortion of the line supply voltage.

Low-frequency harmonics are reduced using line reactors. The high-frequency noise emission can only be reduced if the generated noise current is correctly routed. Using non-shielded motor cables, the noise current flows in an undefined fashion back to the frequency converter, e.g. via foundation/base frame grounders, cable ducts, cabinet frames. These current paths have a very low resistance or currents with a frequency of 50 or 60 Hz. However, the noise current induces a high-frequency component, which can result in problematical voltage drops.

A shielded motor cable is absolutely necessary to enable the fault current to flow back to the frequency converter in a defined fashion.

The shield must be connected to the housing of the frequency converter and to the motor housing through a large surface area. The shield now forms the easiest path for the noise current to take when returning to the frequency converter

(extract from the Masterdrive VC compendium).

Please also see the attached document,. from the same source, that shows how it is recommended to protect the drive and the surrounding plant against harmonics.

Hope this helps,
Daniel Chartier