Specification of the power supply on the Sepam 20 and 40 with respect to harmonics



Goals and Symptoms

What is the tolerance for harmonics of the power suppied to the Sepam 20 and 40?

Causes and Fixes

The Sepam S20 et S40 power supply meet the CEI 255-6 standard. This means:

(a) the range of the fundamental (i.e. 1st harmonic) must be between 47.5 and 63 Hz. the peak value including all the harmonics must not exceed 373 V peak.

(b) the rate of harmonics acceptable is 3% of H2, 8% of H3, 20% of H5, 14% of H7, 9% of H11, 8% of H13 , 6% of H17 and 5% of H19

For example, if one were to ask if it would be acceptable to power the sepam using a square wave (with a lot of a harmonics), the answer could be arrived at as follows:
A square wave is composed of the following:

Since the above equation implies a 3rd hamonic of ~33% (limit stated above for the 3rd is 8%) and a 5th harmonic of 20% (limit stated above for the 5th is 14%), it is clear that a square wave would not conform to the specifications that the power supply was designed to. Thus, it would not be a good idea to deliver a square wave supply to the Sepam device.


  • Last Revised: 8 April 2008

    Applies To: Sepam 20 & 40

    Original Author: CA


    All content © 1992-2008 Schneider Electric


Legacy KB System (APS) Data: RESL192000 V1.0, Originally authored by KBAdPM on 05/23/2008, Last Edited by KBAdPM on 05/23/2008
Related ranges: Sepam series 40, Sepam series 20