What is K-FACTOR?

Today’s modern office buildings and manufacturing plants are dominated by non-linear  loads; desktop computers, solid state ballasts, HID lighting, programmable controllers, and variable speed drives to name a few. Due to these electronic loads, significant harmonic currents have been added to the building’s distribution system. One result is the overheating of transformers causing premature failure. Until now, the only solution has been to de-rate a standard distribution transformer for application on these non-linear loads. De-rating is the operation of a device at less than its rated maximum capability in order to prolong its life. This is no longer acceptable in the industry.
 
Underwriters Laboratories (UL) recognized the problems with de-rating transformers. As a result, new test procedures that coincided with ANSI C57.110- 1986 were established. Today, only those manufacturers that have their transformers evaluated by UL for  harmonic loads can apply the label, “Suitable for Non-Sinusoidal Current Load with K-Factor not to exceed 4, 13, 20, 30, 40, or 50”. To de-rate a standard UL Listed distribution transformer would be a misapplication of that device.
 
What is K-Factor?
K-Factor is a measure of a transformer’s ability to withstand the heating effects of non-sinusoidal harmonic currents created by much of today’s electronic equipment. 
 
ANSI Standard C57.110-1986 addresses harmonic problems in transformers and the design solution. In this standard, the K-Factor is defined and its method of calculation shown. Once the K-Factor is determined, it is used in the design of the transformer to compensate for the additional heating effects generated by the harmonic currents. In short, K-factor is a weighting of the harmonic load currents according to their effects on transformer heating, as derived from ANSI/IEEE C57.110. A K-factor of 1.0 indicates a linear load (no harmonics). The higher the K-factor, the greater the harmonic heating effects. K-Factor ratings are different depending on the load. For example, incandescent lighting will require a K- 1, induction heating equipment: K-4 and mainframe computer loads: K-20.
 
MGM is a leading manufacturer of Non -Sinusoidal Harmonic Transformers for Non Sinusoidal Harmonic loads. The MGM line carries the UL Listing for K -Factor applications from K-1 to K-30.