Compressor Vfd; Drive Board - Carrier 48JCH 04-06 Series Service And Maintenance Instructions

COMPRESSOR VFD

The 48JC units are equipped with a variable speed compressor. To
control this compressor a Variable Frequency Drive (VFD) is re-
quired. This VFD does not look like the typical VFD the industry
might be used to. This VFD is not packaged into its own housing
to appear as a single component, it is comprised of five electronic
components mounted in the unit's control box for the Control box
layout (see Fig. 53). The five components are: The main drive
board, filter board, capacitor board, choke, and converter board.
On 575 volt units the filter board and capacitor board are replaced
with three-phase line reactor.

Drive Board

The drive board is the heart of the VFD. It contains the safety logic
and the power conversations needed for the variable speed
operation. This drive board will take in the 60 Hz supply voltage
and modify it to drive the speed of the compressor, this is done
with voltage and frequency. The drive board is responsible for
monitoring the safety high pressure switch (HPS) and ensure the
compressor is immediately turned off upon HPS trip. There is a
discharge line thermistor (DLT) also provided that the drive board
monitors. This is for situations where there are high line tempera-
tures without the pressure being high enough to indicate a
problem. The drive board has built in logic independent of the
SystemVu logic to fold back the speed of the compressor in the
event of a high current or high temperature situation. This high
current is determine based on the speed ranges, so not just one
current limit. The drive board has its own built in startup and
Converter
SystemVu Controller
Choke
TB4
Board
Fig. 53 — Control Box Layout
speed ramp protections, however these are smaller than what the
SystemVu controller uses. Review the Compressor Control sec-
tion for SystemVu controller start and ramp functions found in the
48/50JC 04-06 Ultra High Efficiency Single Package Rooftop
Units with SystemVu™ Controls Version X.X Controls, Start-
up, Operation and Troubleshooting Instructions manual. There
is a heat sink mounted on the back of this drive board to help cool
the electronics. The drive board only communicates via Modbus
and has local LEDs to show status and errors. The converter board
will be used as the primary interface to this drive board, so refer to
that section for more details. See Fig. 54 and Table 10 on page 35
for more details on the drive board.
UNIT DAMAGE HAZARD
Do not bypass the Drive board and pass the standard power
supply to the compressor, damage may occur.
UNIT DAMAGE HAZARD
If replacing the Drive board remove the whole assembly (heat
sink and electronic board together). Never separate this
assembly on the replacement part.
L1
L2
U
L3
V
GRN
W
HPS
SENSOR
DC- OUT
DC + OUT
RS485
DC- IN DC + IN
Drive Board
CCHR
Power
Supply
IDMR
PMR
34
CAUTION
CAUTION
Capacitor
Board
Filter Board
IGC