Rockwell Automation Low-Voltage Switchgear and Controlgear - Manual (Page 156)

~
=
U
S
EMC
filter
U
C
ASIC
R
Sensor
Interface
Fig. 5.3-1
Example of electronic control of a contactor coil with separate control input
U
S
control supply voltage
U
C
control voltage (PLC)
The advantages of electronically controlled contactor magnet systems:
ƒ Wide control supply voltage range
ƒ Low current consumption
ƒ Clear pull-in and drop-out voltages
ƒ Undervoltage
reliability
ƒ Direct PLC control
ƒ Integrated overvoltage protection circuit
ƒ EMC
compatible
ƒ Small size (usually same as contactors with conventional drive)
ƒ Low noise development
5.3.2 Direct current drives
5.3.2.1 “Conventional”
With direct current, larger magnet systems with specially shaped poles are required to generate
the forces needed for pulling in contactors and to optimize the holding energy. This results, on
the one hand, in a large depth of devices and, on the other, in switching on gentler and in
comparatively low current consumption during pulling-in. The pull-in power is the same as the
holding power. The loading of the control contacts during circuit breaking is relatively high
because of the high inductance of the coils and is taken into account by utilization category
DC-13.
Fig. 5.3-2
Conventional direct current magnet system in the comparison to an alternating current magnet system
and a magnet system with electronic coil control (same size for alternating and direct current)
LVSAM-WP001A-EN-P - April 2009 5-4