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Mains
11 Mains
11.1 Mains Configurations
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:
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 11.1 AC Mains Systems and EMC Characteristics
11.2 Mains Terminal Connections
When connecting the mains, observe the following:
•
Size the wiring based on the input current of the
frequency converter. For maximum wire sizes, see
chapter 6.5 Power-dependent Specifications.
•
Comply with local and national electrical codes
for cable sizes.
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.
MG37N102
Design Guide
2-drive module systems
Illustration 10.8 and Illustration 10.9 show the mains
terminal connections for 6-pulse and 12-pulse 2-drive
systems, respectively.
•
•
•
4-drive module systems
Illustration 10.10 shows the mains terminal connections for
4-drive systems. If a common terminal design is used, there
is 1 set of mains terminals in each cabinet.
11.3 12-pulse Disconnector Configuration
This section describes how to use a disconnector for a 12-
pulse drive system. When using disconnectors or
contactors, make sure to install an interlock. See
Illustration 11.1. When installed, both contactors or discon-
nectors must close to avoid 1 set of rectifiers not working.
Use NC auxiliary contacts with contactors or mains discon-
nectors. Connect the interlock in series with the Klixon
switch of the brake. If only 1 contactor/disconnector has
closed, the LCP shows the error Brake IGBT Fault and does
not allow the drive system to power the motor.
Illustration 11.2 shows a BRF connection with 12-pulse
disconnector and interlock.
Danfoss A/S © 6/2016 All rights reserved.
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 connection of mains 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.
11
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