York YVAA, Installation, Operation & Maintenance Instructions Manual, Page: 18 / 178

JOHNSON CONTROLS
18
FORM 201.28-NM1.1
ISSUE DATE: 1/31/2018
SECTION 2 - PRODUCT DESCRIPTION
Oil separators utilize no moving parts.Oil cooling is
accomplished by refrigerant leaving the eductor flash-
ing in the suction line which cools the oil, motor and
compressor.
An integral liquid cooled, transistorized, PWM,
Variable Speed Drive (VSD) is controlled by the
chiller microprocessor control panel to start/stop, select
compressors to run, and select compressor speed.
Displacement Power Factor is 0. 95 at part or full load.
The chiller microprocessor communicates with the
VSD Logic Board via a 3-wire RS-485 opto coupled
data link. The VSD Logic Board runs the number of
compressors required to meet the load and the com-
pressors to the speed requested by the chiller micro-
processor.
The basic system control and VSD system
architecture is shown in Figure 2 on Page 18 .
FIGURE 2 - CHILLER CONTROL SYSTEM
LD15028
INPUTS
Pressure Transducers
Temperature Sensors
Switches
Liquid Flow
High Pressure
Start/Stop
Level
Customer Supplied
Contacts
CONTROL
PANEL
Chiller Control
Board)
Microprocessor
User Interface
Display and
Keypad
DISPLAY KEYPAD
MOTOR
OUTPUTS
Relay Output Board)
Solenoids
Contactors
Alarm
Pump
Compressor Heater
Run Status
Evaporator Heater
VSD
VSD Logic Board
SCR Trigger Board
Power Components
PWM (Speed Control)
COMMUNICATIONS
Building Automation
Printer Modem
LD15158
3 Phase Power Line
AC/DC Rectifier
Power Driver
IGBT Gate Driver
VSD Logic Board
Inverter
PWM Signal
Signal From Main Control Panel
Rectifier
Compressor 1
Compressor 2
Rectifier Controller
SCR Trigger Board
(IGBT)