Control Wiring Connection; Access; Using Shielded Control Cables; Grounding Of Shielded Control Cables - Danfoss VLT AutomationDrive FC 300 Instruction Manual

Installation

2.5 Control Wiring Connection

2 2
•
Isolate control wiring from high power
components in the adjustable frequency drive
•
If the adjustable frequency drive is connected to
a thermistor, for PELV isolation, optional
thermistor control wiring must be reinforced/
double insulated. A 24 V DC supply voltage is
recommended.

2.5.1 Access

All terminals to the control cables are located underneath
the LCP on the inside of the adjustable frequency drive. To
access, open the door (IP21/54) or remove the front panel
(IP20).

2.5.2 Using Shielded Control Cables

Danfoss recommends braided shielded/armored cables to
optimize EMC immunity of the control cables and the EMC
emission from the motor cables.
The ability of a cable to reduce the incoming and
outgoing radiation of electric noise depends on the
transfer impedance (Z
designed to reduce the transfer of electric noise; however,
a shield with a lower transfer impedance (Z
effective than a shield with a higher transfer impedance
(Z ).
T
Transfer impedance (Z
turers, but it is often possible to estimate transfer
impedance (Z
T
cable.
Transfer impedance (Z
the following factors:
•
The conductibility of the shield material
•
The contact resistance between the individual
shield conductors
•
The shield coverage, i.e., the physical area of the
cable covered by the shield - often stated as a
percentage value
•
Shield type, i.e., braided or twisted pattern
a. Aluminum-clad with copper wire
b. Twisted copper wire or armored steel wire cable
c. Single-layer braided copper wire with varying
percentage shield coverage.
2-22
). The shield of a cable is normally
T
T
) is rarely stated by cable manufac-
T
) by assessing the physical design of the
) can be assessed on the basis of
T
MG34U222 - VLT
®
VLT Automation Drive D-Frame
Instruction Manual
d.
e.
f.
g.
) value is more
Figure 2.24

2.5.3 Grounding of Shielded Control Cables

Correct shielding
The preferred method in most cases is to secure control
and serial communication cables with shielding clamps
provided at both ends to ensure best possible high
frequency cable contact. If the ground potential between
the adjustable frequency drive and the PLC is different,
electric noise may occur that will disturb the entire system.
Solve this problem by fitting an equalizing cable next to
the control cable. Minimum cable cross-section: 0.025 in
2
[16 mm
®
is a registered Danfoss trademark
This is the typical Danfoss reference cable.
Double-layer braided copper wire
Twin layer of braided copper wire with a
magnetic, shielded/armored intermediate layer
Cable that runs in copper tube or steel tube
Lead cable with 0.043 in [1.1 mm] wall thickness
].
2