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Class 8839 58M Enclosed AC Drives
Specifications
182
09/2003
© 2000–2003 Schneider Electric All Rights Reserved
One disconnect shall be common to the
drive controller and bypass contactor.
2. Barriered bypass shall consist of
compartmentalized, multi-door enclosure
construction that provides electrical
isolation of the AC Drive controller from the
bypass contactor using two OSHA and UL
approved disconnects. This configuration
shall remove all power to the drive
controller compartment when the drive
disconnect is in the open position. This
configuration shall allow provide maximum
user flexibility if servicing a drive while
remaining on bypass.
b. A TEST-NORMAL selector switch shall be
used with bypass to allow testing of the AC
Drive without running the motor. In the “Test”
position the isolation contactor shall remain
open preventing motor operation while
operating the AC drive.
c. The operator shall have full operational control
of the bypass starter using a door mounted
AFC/OFF/BYPASS selector switch.
d. Auto transfer to bypass function shall be
provided in the event of drive fault or failure.
This feature shall be enabled or disabled by an
internally mounted selector switch. An
adjustable timer shall provide control of the
delay time between fault and transfer to
bypass.
2.16 HARMONIC MITIGATION EQUIPMENT
REQUIREMENTS
Note to Specifier
: There are several solutions for
effective harmonic mitigation. The most common
approach is the use of a 5% line reactor. When
line reactors are properly sized for the drive
controller, the additional source impedance can
add provide effective levels of harmonic mitigation
for voltage distortion and attenuation of incoming
voltage transients. The alternate approaches
include the use of isolation transformers and
harmonic filters. The typical installation of
isolation transformers and filters are separately
mounted with proper branch circuit protection.
Filters require coordination with the AC Drive
power circuit and must not be part of the bypass
path. An alternate approach is the use of multi-
pulse drives, which are typically specified above
100 hp.
a. The AC Drive shall be provided with a 5%
rated line reactor mounted inside the
enclosure.
b. The AC Drive shall provide provisions and
terminations inside the drive enclosure for
branch circuit protection of a separately
mounted isolation transformer or harmonic
filter. The AC Drive disconnect shall serve as
disconnect for the harmonic filters. Branch
circuit protection shall be in accordance with
the NEC using fused protection. Harmonic
filters shall be isolated from bypass path
operation if supplied.
2.17 HARMONIC ANALYSIS
Note to Specifier
: Guidelines for voltage and
current distortion are addressed in IEEE Standard
519-1992 titled “IEEE Recommended Practices
and Requirements for Harmonic Control in
Electrical Power Systems”, which suggests
distortion limits dependent upon the electric
power distribution system for industrial and
commercial consumers. Collectively, all facility
loads and the building electrical distribution
network determines the harmonic levels at the
user & electric utility interface. The Electrical
Power Research Institute (EPRI) recognizes the
‘Point of Common Coupling’ or PCC as the
interface between user and electric utility (energy
meter) in the electrical distribution network. The
AC Drives manufacturer can provide calculations
through computer modeling, specific to the
installation, showing total harmonic voltage
distortion. Contractor to provide one line diagram
drawings to supplier including transformer
impedance. The AC Drive manufacturer needs
this information.
a. A harmonic distortion analysis shall be
performed and priced as a separate line item
by the AC Drive manufacturer based upon
documentation supplied by the contractor. The
documentation shall consist of one-line
diagrams, distribution transformer information
(kVA, %Z, and X/R ratio) and emergency
standby generator performance
specifications. The harmonic distortion
analysis report shall be part of the approval
drawing process, submitted to the engineer for
approval.
b. If the calculations determine that harmonic
distortion values are higher than the voltage
and current values specified, the drive
manufacturer shall provide [line reactors,
isolation transformers, harmonic suppressors]
to meet the intent of IEEE 519-1992
guidelines.