Using Screened Control Cables; Control Terminal Functions - Danfoss VLT HVAC Operating Instructions Manual

Installation
1
Illustration 2.17 Connecting Control Wiring

2.4.5.4 Using Screened Control Cables

Correct screening
The preferred method in most cases is to secure control
and serial communication cables with screening clamps
provided at both ends to ensure best possible high
frequency cable contact.
If the earth potential between the frequency converter 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: 16 mm 2 .
PLC
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1
2
Illustration 2.18
50/60 Hz ground loops
With very long control cables, ground loops may occur. To
eliminate ground loops, connect one end of the screen-to-
ground with a 100nF capacitor (keeping leads short).
PLC
PE
100nF
Illustration 2.19
Avoid EMC noise on serial communication
This terminal is connected to earth via an internal RC link.
Use twisted-pair cables to reduce interference between
conductors. The recommended method is shown below:
®
VLT HVAC Drive Operating Instructions
2
FC
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FC
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MG11AH02 - VLT is a registered Danfoss trademark
FC
69
68
61
PE
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2
Illustration 2.20
Alternatively, the connection to terminal 61 can be
omitted:
FC
69
68
PE
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1
2
Illustration 2.21

2.4.5.5 Control Terminal Functions

Frequency converter functions are commanded by
receiving control input signals.
•
Each terminal must be programmed for the
function it will be supporting in the parameters
associated with that terminal. SeeTable 2.4 for
terminals and associated parameters.
•
It is important to confirm that the control
terminal is programmed for the correct function.
See 4 User Interface for details on accessing
parameters and 5 About Frequency Converter
Programming for details on programming.
•
The default terminal programming is intended to
initiate frequency converter functioning in a
typical operational mode.
2.4.5.6 Jumper Terminals 12 and 27
A jumper wire may be required between terminal 12 (or
13) and terminal 27 for the frequency converter to operate
when using factory default programming values.
•
Digital input terminal 27 is designed to receive an
24 V DC external interlock command. In many
applications, the user wires an external interlock
device to terminal 27
•
When no interlock device is used, wire a jumper
between control terminal 12 (recommended) or
13 to terminal 27. This provides in internal 24 V
signal on terminal 27
•
No signal present prevents the unit from
operating
•
When the status line at the bottom of the LCP
reads AUTO REMOTE COASTING or Alarm 60
FC
69
68
61
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1
FC
68
69
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19
2 2