York VSD 292, Operation Manual

Page: 15 / 46

JOHNSON CONTROLS
15
SECTION 1 - GENERAL INFORMATION
FORM 160.00-O4
ISSUE DATE: 07/31/2019
1
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 con-
verter. 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 con-
tain an optional Harmonic Filter. The “trap” filter is
composed of a series of capacitors, inductors, and re-
sistors. 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
Within the drive model number nomenclature there are
2 different letters for the design center of the drive. A
‘G’ for the design center is a drive that is designed to
the UL and CE requirements. A ‘W’ for the design cen-
ter 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 cool-
ing 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 cool-
ing 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 har-
monic filter system can be included in the drive enclo-
sure. The VSD model also contains the control wiring,
additional cooling capacity, and pre-charge 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 sys-
tem 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 2 designs.
OPTISPEED COMPRESSOR DRIVE CONTROL
SYSTEM OVERVIEW
The OSCD control system can be connected to a Mi-
crocomputer Control Center or to an OptiView Control
Center. Regardless of which control center is used each
component performs the same function.
The OSCD control system is composed of various
components located within both the Control Center
and the OSCD. Thus integrating the Control Center
with the OSCD. The OSCD system utilizes various
microprocessors, which are linked together through a
network of communications links.
The Control Center before 2005
The Control Center contains two boards that act upon
OSCD related information, the Microboard and the
Adaptive Capacity Control board (ACC). The ACC
board performs two major functions in the OSCD con-
trol system - (1) to act as a gateway for information
flow between the Control Center and the OSCD. (2) To
determine the optimum operating speed for maximum
chiller system efficiency.
The ACC board acts as an information gateway for all
data flowing between the OSCD and the Control Cen-
ter. The ACC board has a communication link to the
OSCD logic board, and one communication link from
the optional Harmonic Filter logic board. Once the
ACC board receives the information, the information
is then passed onto the Control Center via a software
communication link. The Microcomputer Control Cen-
ter communicates in a parallel fashion via two ribbon
cables connecting the ACC board to the Microboard.
The OptiView™ Control Center communicates
through communications port via a bi-directional serial
port via a three wire cable connecting the ACC board
to the Microboard.
In order to achieve the most efficient operation of a cen-
trifugal compressor, the speed of the compressor must
be reduced to match the “lift” or “head” of the load.
This “lift” or “head” is determined by the evaporator
and condenser refrigerant pressures. However, if the
compressor speed is reduced too much, the refrigerant
gas will flow backwards through the compressor wheel
causing the compressor to “surge”, an undesirable and
extremely inefficient operating condition. Thus there
exists one particular optimum operating speed (on the
“edge” of surge) for a given head, which provides the
optimum system efficiency.