Johnson Controls YCIV0157, Установка, эксплуатация и обслуживание

Страница: 30 / 334

JOHNSON CONTROLS
30
FORM 201.23-NM2
ISSUE DATE: 3/9/2015
SECTION 2 - PRODUCT DESCRIPTION
The DC to AC inverter section of the VSD serves to
convert the rectified and filtered DC back to AC at the
magnitude and frequency commanded by the VSD
Logic Board. The inverter section is actually composed
of two to four identical inverter output phase assem-
blies. These assemblies are in turn composed of 3 pairs
of Insulated Gate Bipolar Transistor (IGBT) modules
mounted to a liquid cooled heatsink, and a IGBT Gate
Driver Board, which provides the ON and OFF gating
pulses to the IGBT’s as determined by the VSD Logic
Board. In order to minimize the parasitic inductance
between the IGBT’s and the capacitor banks, copper
plates, which electrically connect the capacitors to one
another and to the IGBT’s are connected together using
a “laminated bus” structure.
This “laminated bus” structure is a actually composed
of a pair of copper bus plates with a thin sheet of in-
sulating material acting as the separator/insulator. The
“laminated bus” structure forms a parasitic capacitor,
which acts as a small valued capacitor, effectively can-
celing the parasitic inductance of the bus bars them-
selves. To further cancel the parasitic inductances, a
series of small film capacitors are connected between
the positive and negative plates of the DC link.
The VSD output suppression network is composed
of a series of capacitors and resistors connected in a
three phase delta configuration. The parameters of the
suppression network components are chosen to work
in unison with the parasitic inductance of the DC to
AC inverter sections in order to simultaneously limit
both the rate of change of voltage and the peak voltage
applied to the motor windings. By limiting the peak
voltage to the motor windings, as well as the rate-of-
change of motor voltage, we can avoid problems com-
monly associated with PWM motor drives, such as
stator-winding end-turn failures and electrical fluting
of motor bearings.
The VSD is cooled by a propylene glycol cooling
loop. The loop utilizes a glycol pump, which pumps
glycol through the VSD heatsinks to cool the power
components. The glycol is then circulated through the
condenser to reject the heat from the VSD. The cooled
glycol is then circulated back through the loop.
Various ancillary sensors and boards are used to send
information back to the VSD Logic Board. Each IGBT
Power Module within the DC to AC inverter section
contains a thermistor heatsink temperature sensor to
provide temperature information to the VSD Logic
Board. The Bus Isolator board utilizes three resistors
on the board to provide a “safe” impedance (resis-
tance) between the DC link filter capacitors located on
the output phase bank assemblies and the VSD Logic
Board. It provides the means to sense the positive, mid-
point and negative connection points of the VSD’s DC
link without applying high voltage to the VSD Logic
Board. A Current transformer is included on each out-
put phase assembly to provide motor current informa-
tion to the VSD Logic Board.
ACCESSORIES AND OPTIONS
Sound Reduction Options
The standard chiller has fans that operate at normal
speed, no compressor enclosure, and is typically used
in non-sensitive sound areas such as industrial areas or
locations with loud traffic background noise. One or
more of the following sound reduction options may be
employed by the system designer as normally gener-
ated machine noise is considered in the overall project
design.
Ultra Quiet Fans
With this option, the basic chiller is equipped with spe-
cially designed fans and motors to provide lower sound
levels and retain appropriate airflow. The result is re-
duced fan generated noise with minimal effect on the
chiller capacity or efficiency at standard AHRI condi-
tions. (Factory-mounted)
Two-Speed Fans
With this option, the basic chiller is equipped with fans
designed with two operating speeds. At high ambient
conditions the fans operate at the normal speed with
sound levels equivalent to Ultra Quiet Fans. As the am-
bient temperature falls, the fans automatically reduce
to slow speed reducing sound levels. If very low sound
is required at all ambient conditions normal fan speed
can be inhibited. (Factory-mounted)
Reduced Sound Option
With this option the chiller is equipped with an unlined
compressor enclosure. This option is typically used for
daytime operation where background noise is lower
than normal city traffic etc.
(Factory-mounted)
Low Sound Option
This option is only available with the selection of Ultra
Quiet Fans or Two-Speed Fans. The chiller is equipped
with an acoustically lined compressor enclosure. This
option is typically for locations near residential ar-
eas, hotels, or hospitals etc., where background noise
is limited. When paired with the Two-Speed Fan op-