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 K-Factor
Harmonic Transformers
In today's industrial
workplace, the proliferation of solid state devices (lighting ballasts, motor drives and
controls, communications equipment, and other DC-powered loads) has created a major
problem for specifying engineers, contractors and building owners. The non-linear nature
of their switch mode power supplies generate harmonic currents that cause transformers and
system neutrals to overheat and destroy themselves.
K-Factor
transformers are designed to reduce the heating effects of harmonic
currents created by loads like those shown in Chart A. The K-Factor
rating is an index of the transformer's ability to withstand harmonic
content while operating within the temperature limits of its insulating
system. Sola/Hevi-Duty K-Factor transformers have UL ratings of
K-4, K-13 and K-20.
The Sola/Hevi-Duty K-Factor design is a specialized transformer
that offers these benefits:
- Conductors
capable of carrying the harmonic currents of non-linear loads
without exceeding the temperature rating of the insulation system.
Paralleled conductors are used to reduce and control skin effect
losses.
- A
transformer design that takes into account the increase in naturally
occurring "stray" losses caused by non-linear loads.
These losses cause standard transformers to dramatically overheat
and substantially shorten design life. The K-Factor is designed
to function within safe operating temperatures.
- A
core and coil design that manages the DC flux caused by triplen
harmonics*. As these harmonics increase, they cause additional
current to circulate in the delta winding. This produces a DC
flux in the core which leads to core saturation, voltage instability
and overheating.
- K-Factor
transformers are UL 1561 listed.
- Designed
to supply non-linear loads without overheating the windings or
saturating the core.
- All
Sola/Hevi-Duty K-Factor transformers have a rated temperature
rise of 150°C.
- Contact
Technical Services
for weather shield information.
* Triplen
harmonics are those harmonics which are odd multiples of third harmonic
(9th, 15th, 21st, etc.).
On this page:
Features, Typical Load K-Factors,
Accessories, Selection Tables, Electrical Connection, Design Style
A
printable version of the following section is available by selecting
the pdf file to the left.
- Conductors
to carry harmonics of a K-rated load without exceeding insulation
temperature ratings
- UL
1561 listed up to K-20 rated protection
- Rated
temperature rise of 150°C, 220°C insulation
- Shielded
for quality power
- Basic
design takes "stray losses" into account and functions
within safe operating temperatures
- Core
and coil design engineered to manage the zero sequence flox caused
by triplen harmonics
- Provides
100% rated current without overheating the windings
or saturating the core
| Load |
K-Factor |
| Electric discharge lighting |
K-4 |
| UPS with optional input filtering |
K-4 |
| Welders |
K-4 |
| Induction heating equipment |
K-4 |
| PLCs and solid state controls (other
than variable speed drives) |
K-4 |
| Telecommunications equipment (e.g.
PBX) |
K-13 |
| UPS without input filtering |
K-13 |
Multiwire receptacle circuits in
general care areas of health care facilities
and classrooms of schools, etc. |
K-13 |
Multiwire receptacle circuits
supplying inspection or testing equipment on an
assembly or production line |
K-13 |
| Mainframe computer loads |
K-20 |
| Solid state motor drives (variable
speed drives) |
K-20 |
| Multiwire receptacle circuits in
critical care areas and operating/recovery rooms of hospitals |
K-20 |
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*Reprinted with permission from
EDI Magazine
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• Wall mounting brackets (through 45 KVA only)
• Weather Shields (UL-3R)
• Stainless Steel Enclosures
• Totally enclosed non-ventilated designs
• Low temperature rise units available
• Open core and coil designs
• Copper Wound designs
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