2.6 Serial Communication
RS-485 is a two-wire bus interface compatible with multi-
drop network topology, i.e. nodes can be connected as a
bus, or via drop cables from a common trunk line. A total
of 32 nodes can be connected to one network segment.
Repeaters divide network segments. Each repeater
functions as a node within the segment in which it is
installed. Each node connected within a given network
must have a unique node address across all segments.
Terminate each segment at both ends, using either the
termination switch (S801) of the frequency converter or a
biased termination resistor network. Always use screened
twisted pair (STP) cable for bus cabling, and always follow
good common installation practice.
Low-impedance earth (ground) connection of the screen at
every node is important, including at high frequencies.
Thus, connect a large surface of the screen to earth
(ground), for example with a cable clamp or a conductive
cable gland. It may be necessary to apply potential-
equalizing cables to maintain the same earth (ground)
potential throughout the network. Particularly in instal-
lations with long cables.
To prevent impedance mismatch, always use the same
type of cable throughout the entire network. When
connecting a motor to the frequency converter, always use
screened motor cable.
Cable
Screened twisted pair (STP)
Impedance
120
Ω
Max. cable length
1200 m (including drop lines)
500 m station-to-station
Table 2.11
2.7 Optional Equipment
2.7.1 Load Share Terminals
Load share terminals enable the connection of the DC
circuits of several frequency converters. Load share
terminals are available in IP20 frequency converters and
extend out the top of the frequency converter. A terminal
cover, supplied with the frequency converter, must be
installed to maintain the IP20 rating of the enclosure.
shows both the covered and uncovered
terminals.
130BC547.10
Illustration 2.32 Load Share or Regeneration Terminal with Cover
(L) and without Cover (R)
2.7.2 Regeneration Terminals
Regen (regeneration) terminals can be supplied for
applications that have a regenerative load. A regenerative
unit, supplied by a third party, connects to the regen
terminals so that power can be regenerated back onto the
mains, resulting in energy savings. Regen terminals are
available in IP20 frequency converters and extend out the
top of the frequency converter. A terminal cover, supplied
with the frequency converter, must be installed to
maintain the IP20 rating of the enclosure.
shows both the covered and uncovered terminals.
2.7.3 Anti-condensation Heater
An anti-condensation heater can be installed inside the
frequency converter to prevent condensation from forming
inside the enclosure when the unit is turned off. The
heater is controlled by customer-supplied 230 V AC. For
best results, operate the heater only when the unit is not
running and turn the heater off when the unit is running.
2.7.4 Brake Chopper
A brake chopper can be supplied for applications that
have a regenerative load. The brake chopper connects to a
brake resistor, which consumes the braking energy,
preventing an overvoltage fault on the DC bus. The
braking chopper is automatically activated when the DC
bus voltage exceeds a specified level, depending on the
nominal voltage of the frequency converter.
2.7.5 Mains Shield
The mains shield is a Lexan cover installed inside the
enclosure to provide protection according to VBG-4
accident-prevention requirements.
Installation
VLT
®
AQUA Drive D-Frame
Operating Instructions
30
MG21A202 - VLT
®
is a registered Danfoss trademark
2
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