Variable Frequency Drives offer many advantages such as energy conservation, ability to control speed precisely and accurately, improvement in product quality and productivity, etc. However the output of VFD is a PWM-wave, which is far from a pure sine wave. Due to this AVFD can create problems such as: Increased heating of AC motors. Degradation of motor winding due to additional voltage spikes applied to motor windings, when the distance between motor and inverter is more than 50 meters Increased motor-audible noise. Reduced motor efficiency Increased heat in motor bearings, reducing the motors life.

Figure1 shows The System Configuration With Sinus Filter .

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Sinus filter, if properly applied results in following ADVANTAGES:

1. Increased motor life due to reduced harmonics, less heating, elimination of bearing current

2. Reduced motor audible noise.

3. Elimination of voltage spikes on motor winding, due to very long cable between motor and inverter,
where even output choke is less effective.

4. Reduced conducted and radiated noise.