Mains Connections; Ac Mains Terminal Connections; Mains Terminal Connections In 2-Drive Module Systems - Danfoss VLT FC 102 Installation Manual

Electrical Installation

5.8 Mains Connections

There are several types of AC mains systems for supplying
power to frequency converters. Each affects the EMC
characteristics of the system. The 5-wire TN-S systems are
regarded as best regarding EMC, while the isolated IT
system is the least preferred.
System Description
type
TN mains There are 2 types of TN mains distribution systems:
5 5 systems TN-S and TN-C.
TN-S A 5-wire system with separate neutral (N) and
protective earth (PE) conductors. It provides the
best EMC properties and avoids transmitting
interference.
TN-C A 4-wire system with a common neutral and
protective earth (PE) conductor throughout the
system. The combined neutral and PE conductor
results in poor EMC characteristics.
TT mains A 4-wire system with a grounded neutral conductor
systems and individual grounding of the drive system. It has
good EMC characteristics when grounded properly.
IT grid An isolated 4-wire system with the neutral
system conductor either not grounded or grounded via an
impedance.
Table 5.11 AC Mains Systems and EMC Characteristics

5.8.1 AC Mains Terminal Connections

When making mains connections, observe the following:
•
Size the wiring based on the input current of the
frequency converter. For maximum wire sizes, see
chapter 7.1 Power-dependent Specifications.
•
Comply with local and national electrical codes
for cable sizes.
28
®
VLT Parallel Drive Modules
5.8.1.1 Mains Terminal Connections in 2-
Illustration 8.9 and Illustration 8.10 show the bus bar
connections for 6-pulse and 12-pulse 2-drive systems,
respectively.
•
•
•
NOTICE
MULTIPLE MAINS CABLES
If connecting more than 1 set of mains terminals, use the
same number, size, and length of cables for each set of
terminals. For example, do not use 1 cable on one mains
terminal and 2 cables on another mains terminal.
1.
2.
3.
4.
5.
6.
Danfoss A/S © 08/2017 All rights reserved.
Drive Module Systems
If a common terminal design is used with a 6-
pulse, 2-drive system, there is 1 set of mains
terminals.
Common terminal design cannot be used with
12-pulse mains connections in a 2-drive module
systems. The mains cables are connected directly
to the drive input terminals.
There are individual brake terminals available in
each drive module. Connect an equal number of
recommended cables to the individual brake
terminals.
Measure between the common terminals and the
first common point of a phase, typically the
mains terminals.
For 12-pulse drive modules, the set of cables from
the 1 st drive module connects to the star-
secondary winding of the 12-pulse transformer.
nd
The set from the 2 drive module connects to
the delta-secondary winding of the 12-pulse
transformer.
Strip a section of the outer cable insulation.
Connect the ground wire to the nearest ground
terminal.
Connect the 3-phase mains wiring to terminals
R/91, S/92, and T/93 using M10 screws.
Tighten the mains terminals. See
chapter 7.9.1 Tightening Torques for Terminals.
MG37K302