The three-phase inductor provides some impedance for the filter to “work against”. It effectively
limits the rate of change in current at the input to the filter to a reason- able level.
The Filter Power Unit is the most complicated power component in the optional filter. Its purpose
is to generate the harmonic currents required by the OSCD’s AC-to-DC converter so that these
harmonic currents are not drawn from the AC line. The Filter Power Unit is identical to the OSCD's
Power Unit in the 351 hp drive, except for two fewer capacitors in the filter capacitor “bank”, and
a smaller transistor module and modified gate driver board. The Harmonic Filter Gate Driver
board provides turn on and turn off commands as determined by the Harmonic Filter Logic board.
“Bleeder” resistors are mounted on the side of the Filter Power Unit to provide a discharge path for
the DC bus capacitors.
Other sensors and boards are used to provide safe operation of the harmonic filter. The transistor
module contains a temperature sensor that provides temperature information back to the Filter
Logic Board. This sensor protects the filter transistor module from over temperature conditions.
A Bus Isolator board is used to ensure that the DC bus capacitors are properly charged and the
voltage is balanced. Two output current sensors are used to protect the filter against an over
current or an overload condition. Input current transformers sense the input current drawn by the
OSCD’s AC to DC converter. The Line Voltage Isolation board provides AC line voltage information
to the Harmonic Filter Logic board. This information is used to determine the proper bus voltage
value.
The “trap” filter is standard on all OSCD's that contain an optional Harmonic Filter. The “trap” filter
is composed of a series of capacitors, inductors, and resistors. The “trap” filter is used to reduce the
effects of the PWM switching frequency of the filter on the power source.
Differences between the G and W designs
The drive model number nomenclature has two different letters for the design center of the drive.
The G for the design center is a drive that is designed to the UL and CE requirements. The W for the
design center is a drive that is designed to standards that govern products built for the Asia market.
The way the drive functions, protects itself, and the motor are the same for both designs. The W
design takes advantage of local components, and local manufacturing. The cooling system is the
area where most of the changes occur and only effect the 50 Hz application. The W design solves
the problem of reduce cooling because of 50 Hz power by using a large cooling fan and a different
cooling pump. The cooling fan and pump require a 230 VAC 50 Hz source. This higher power source
allows the fan and pump to provide the same amount of cooling as the 60 Hz application. The
230 VAC source is provided by an additional voltage tap from the control transformer. This new
transformer provides the voltage required for the 230 VAC and 120 VAC components.
Differences for the VSD and LVD model drives
The VSD model drives are designed so that the harmonic filter system can be included in the
drive enclosure. The VSD model also contains the control wiring, additional cooling capacity, and
precharge resistors for the harmonic filter system, regardless if the harmonic filter system is
installed or not. This process allowed for an easier method to retrofit the harmonic filter system
later if the customer desired. The LVD model does not contain any support for the harmonic filter
system. The enclosure size is reduced, and the harmonic filter cannot be added as an option later.
The function of the drive is identical between the two designs.
OptiSpeed compressor drive control system overview
The OSCD control system can be connected to a Microcomputer Control Center or to an OptiView
Control Center. Regardless of which control center is used each component performs the same
function.
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Liquid-Cooled OptiSpeed Compressor Speed Drive
