Capstone Turbine Corporation • 16640 Stagg Street • Van Nuys • CA 91406 • USA
Installation Guide: Capstone C1000S/C800S/C600S with C1000 Series Controller
480064 Rev C (December 2018) Page 107 of 122
Capstone reserves the right to change or modify, without notice, the design, specifications, and/or contents of this document without
incurring any obligation either with respect to equipment previously sold or in the process of construction.
Harmonics cause an increase in eddy currents in the transformer core, which in turn increase
heat in the transformer and may damage the insulation on windings, causing serious problems.
With high current harmonics, a transformer may not have enough capacity for a specific load,
even if the transformer capacity is sized for the load.
K-factor is a means to quantify the harmonic load currents and their heating effect on a
transformer. A K-factor of 1.0 indicates a linear load (no harmonics); a higher K-factor value
indicates a higher heating effect on the transformer.
Generally, only manufacturers of larger transformers (>1 MVA) will offer different K-factor ratings.
Hence, it becomes important to oversize smaller transformers operating on non-linear loads. Most
K-factor rated transformers are custom-built, so in some cases it is more economical to simply
oversize the transformer.
As a rule, the smallest transformer that should be tied to the output of a SA microturbine
should not be smaller than 45 kVA, even if the connected load is much smaller.
When powering high harmonic loads (>8% THD in current), the transformer should be
oversized by 40% at a minimum.
If specifying the K-factor of the transformer is possible, a K-factor between 9 and 13 is
recommended for loads with high harmonics (>8% THD in current). Even with an oversized
transformer or a transformer with a high K rating, it is highly recommended to always keep the
load harmonics to a minimum.
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