Cut Sheet

4
Technical Data TD01701001E
Effective March 2017
UL low-voltage busway
Pow-R-Way III
EATON www.eaton.com
200% neutral option (Figure 4)
Pow-R-Way III offers a fully rated, 200% neutral bus option for
busway fed distribution systems with nonlinear loads. The additional
neutral capacity prevents the overheating caused by zero sequence
harmonic currents. The Pow-R-Way III 200% neutral is manufactured
with a single 0.50 inch (12.7 mm) thick bus bar that receives the
same silver-plating and Class B, 130 °C Epoxy insulation as the
phase bars.
Power system harmonics are generated by various types of non-
linear loads. A sinusoidal voltage applied to a nonlinear load will
result in a non-sinusoidal current and waveform distortion. Loads
that are switched or pulsed, such as rectifiers, thyristors, and
switch-mode power supplies, are nonlinear. With the proliferation of
electronics into industrial, commercial, and institutional applications,
nonlinear loads have become a significant and critical component
of most modern distribution and control systems. Examples of
nonlinear loads are personal computers, UPS systems, variable
frequency motor controllers, electronic lighting ballasts, fax and
copying machines, medical test equipment, and many other
microprocessor-based apparatus.
Nonlinear load currents typically are extremely high in harmonic
content. The harmonics create numerous problems in electrical
systems and equipment. Some harmonics are negative sequence
with 120° phase displacement (this means the phase rotation is
ACB instead of ABC). Positive sequence harmonics have 120°
phase displacement, but are of the same rotation as the distribution
system. Certain nonlinear loads cause odd triplen harmonics, which
are zero sequence with no phase displacement.
Balancing the phase load currents in a three-phase, four-wire system
will normally reduce neutral currents to zero if load currents have an
undistorted sinusoidal waveform. However, because zero sequence
harmonics are additive and will not cancel each other in the neutral,
the neutral current can be as high as 1.73 times the phase current,
even with the phase currents perfectly balanced. This can result
in overheated neutrals and lead to deterioration of equipment
performance and a shortened equipment life cycle.
The Computer and Business Equipment Manufacturers Association
(CBEMA) recommends that neutrals be oversized to at least 173%
of the ampacity of the phase conductors to prevent problems.
Pow-R-Way III offers a fully rated, 200% neutral bus option for
busway fed distribution systems with non-sinusoidal loads. The
additional neutral capacity prevents the overheating caused by
high harmonic neutral currents.
Figure 4. 200% Neutral cross section
UL fire stop system
Pow-R-Way III busway may be used in UL Listed through-penetration
fire stop systems. Systems applicable to busway e.g., system
number C-AJ-6002) are listed in the UL Fire Resistance Directory
under “Through-Penetration Fire Stop Systems” and have met the
ASTEM E814 (UL 1479) criteria.
For typical installations shown in Figure 5, the installing contractor
uses mineral wool batt and fire stop sealant. In riser applications,
the system is used in combination with Pow-R-Way III vertical spring
hangers and a floor flange. In horizontal applications, the system is
used in combination with two wall flanges, one on each side of the
wall, and sealant.
ote:N This information is provided as a guideline for typical fire stop systems.
Consult the fire stop system sealant manufacturer for the UL file number and
specific product information.
Figure 5. Typical installations of Pow-R-Way III in fire
stop systems
DTI SmartBolts
DTI SmartBolts
®
are an optional torque/tension indicating bolt
that can be used in any standard Pow-R-Way III bridge joint
(see page 5, Pow-R-Bridge Joint). In place of checking each joint
connection with a torque wrench, DTI SmartBolts
®
provide a visible
indication of a loose or tensioned condition. The bright red indication
of a loose fastener will gradually darken as the fastener is tightened
until it turns to a deep black color, indicating that the joint has
been tightened to the proper torque/tension. Standard preventive
maintenance becomes a simple and safe visual inspection.
Figure 6. DTI SmartBolts
Top
Pow-R-Way III, Three-Phase Four-Wire
with Housing Ground and 200% Neutral
A
B
C
N
Floor Flange
12 Ga Steel
Mounting
Support
Vertical
Hanger
T
Floor
Fire stop Material
Suggest 3m, Specied
Technologies, or Equivalent
Manufacturer Fire Stop
Products—UL 1479 Listed
Floor Flange (Optional)
UL Listed Pow-R-Way III
Busway