3.6.8 Serial Communication Cable Connection
Connect the RS-485 cable(s) to the PCB of the Variable Speed Drive as follows, see
:
1.
Attach the positive (+) polarity wire to the screw terminal.
2.
Attach the negative (-) polarity wire to the screw terminal.
3.
Attach the drain cable to the drain terminal (D).
4.
Attach the cable with the shield to the compression clamp on the chassis.
5.
Connect the other end of the RS-485 cable to the OEM Controller ensuring that the polarity of the wires matches
the polarity at the drive.
The two 3-pole connectors are marked on the circuit board as “Master” which connects to the OEM Controller, and “EEV_1”
which connects to the indoor EEV Controller (separate internal Danfoss bus).
The compression clamp is suitable to two sets of cable. Make sure to establish a good connection between the shield and
the compression clamp and the chassis.
175ZB024.12
Shield
MASTER
EEV_1
Illustration 3.13 Serial Communication Connection Cable
When selecting a transmission line for RS-485, it is necessary to examine the required distance of the cable and the data
rate of the system. Losses in a transmission line are a combination of AC losses (skin effect), DC conductor loss, leakage, and
AC losses in the dielectric. In high-quality cable, the conductor losses and the dielectric losses are on the same order of
magnitude.
The recommended maximum Modbus cable length between the drive and the OEM Controller should not exceed 100 ft (30
m).
While the RS-485 specification does not specify cabling, the recommendation is 24 AWG shielded twisted-pair cable with a
shunt capacitance of 16 pF/ft and 100
Ω
impedance.It is also possible to use the same cable commonly in the twisted-pair
Ethernet cabling. This cable is commonly referred to as Category 5 cable. The cable has a maximum capacitance of 17 pF/ft
(14.5 pF/ft typical) and characteristic impedance of 100
Ω
.
Electrical Installation
VLT
®
Inverter Scroll CDS 801 Operating Instructions
MG10V402 - VLT
®
is a registered Danfoss trademark
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