Triplen transformer technology (Page 1 of 2)

Third harmonic effects
The third harmonic component of a computer load current is the largest single harmonic component and is typically at least 30% and potentially greater than 80%. Compared to the third, other triplen harmonics may be neglected.

The presence of this harmonic in a distribution system can cause overloading of the neutral cable as well as voltage distortion.

Overloading of the neutral cable
If the percentage of third harmonic in the load is 70%, a not uncommon figure, and the phase currents are 100% then the current in the neutral conductor due to the third harmonic will be:

• 70% from phase A + 70% from phase B + 70% from phase C

This results in a total neutral current of 210%. As neutral conductors are generally not protected, damage to the neutral conductor will result.