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The
harmonic frequencies are exact multiples of the fundamental
supply frequency.
Typically the harmonics which are
generated by3 phase 6-pulse rectifiers in the common
AC or DC drives just include the harmonics numbers 5,
7, 11, 13, 17, 19, 23 & 25 etc.
Harmonic currents affect the circuit
components which are direct on the line supplying the
drive, such as transformers, cables and circuit breakers.
The
most sensitive are transformers, because the losses
in windings and cores are higher with higher amount
of harmonic currents. If the non-linear load percentage
of the total transformer load is going to be more than
50%, it is important to check the transformers loadability.
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Distorted wave composed by the superposition
of a 60 Hz fundamental and small third harmonic and
fifth harmonics.
System
Harmonic Calculator
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Harmonic
voltage affect all equipment which are connected to the supply.
Ways to reduce harmonic distortion
Use PWM AC drive
Choose drive with effective DC Line Filtering
If possible use 12-pulse Rectifier in the
Drive
Install the cabling and earthing properly
Install Shunt Filters or Harmonic Traps
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