Rockwell Automation Low-Voltage Switchgear and Controlgear - Manual (Page 5)

0 Table of contents
0 Table of contents .................................................................................................. 0-5
1 Load characteristics and utilization categories................................................. 1-1
1.1 Utilization categories simplify the selection of devices ................................... 1-1
1.2 Electrical heating devices .................................................................................... 1-4
1.3 Lamps and illumination equipment .................................................................... 1-4
1.3.1 Incandescent lamps................................................................................................ 1-4
1.3.1.1 Halogen lamps ........................................................................................................ 1-4
1.3.2 Discharge lamps ..................................................................................................... 1-4
1.4 Transformers......................................................................................................... 1-5
1.5 Reactive power compensation and switching of capacitors............................ 1-6
1.5.1 Reactive power compensation................................................................................ 1-6
1.5.1.1 Individual compensation ......................................................................................... 1-6
1.5.1.2 Group compensation .............................................................................................. 1-7
1.5.1.3 Central compensation............................................................................................. 1-7
1.5.2 Switching of capacitors ........................................................................................... 1-7
1.5.2.1 Switching-on single capacitors ............................................................................... 1-8
1.5.2.2 Switching of long, screened lines ........................................................................... 1-8
1.5.2.3 Switching capacitors of central compensation units ............................................... 1-8
1.6 Control circuits, semiconductor load and electromagnetic load..................... 1-9
1.7 Three-phase asynchronous motors.................................................................... 1-9
1.7.1 Principle of operation .............................................................................................. 1-9
1.7.1.1 Slip-ring motors..................................................................................................... 1-11
1.7.1.2 Squirrel-cage induction motors ............................................................................. 1-12
1.7.1.2.1 High efficiency motors .......................................................................................... 1-14
1.7.1.3 Influence of the voltage across the windings ........................................................ 1-15
1.7.1.4 Performance of squirrel-cage induction motors with changing frequency ............ 1-16
2 Switching tasks and selecting the appropriate switchgear.............................. 2-1
2.1 Electrical equipment complying with standards and matching
the application requirements............................................................................... 2-1
2.2 Basic switching tasks and criteria for device selection ................................... 2-1
2.2.1 Device types ........................................................................................................... 2-2
2.2.1.1 Disconnectors (isolating switches).......................................................................... 2-2
2.2.1.2 Load switches ......................................................................................................... 2-3
2.2.1.3 Switch disconnectors .............................................................................................. 2-3
2.2.1.4 Circuit breakers....................................................................................................... 2-3
2.2.1.5 Supply disconnecting devices................................................................................. 2-3
2.2.1.6 Supply disconnecting EMERGENCY STOP devices.............................................. 2-4
2.2.1.7 Summary supply disconnect and EMERGENCY STOP devices............................ 2-5
2.2.1.8 Fuses ...................................................................................................................... 2-5
2.2.1.9 Devices for thermal protection ................................................................................ 2-5
2.2.1.10 Contactors .............................................................................................................. 2-5
2.3 Parameters for the correct selection and sizing................................................ 2-5
2.3.1 Rated isolation voltage U
i
....................................................................................... 2-7
U
2.3.2 Rated operational voltage U
e
, rated operational current I
e
and utilization category 2-7
U
2.3.3 Rated impulse withstand voltage U
imp
..................................................................... 2-7
U
2.3.4 Short-circuit withstand capacity and short-circuit protection ................................... 2-9
2.3.4.1 Joule integral I 2 t .................................................................................................... 2-10
2.3.4.2 Cut-off current I
D
................................................................................................... 2-10
2.3.4.3 Rated short-time withstand current l
CW
................................................................. 2-10
LVSAM-WP001A-EN-P - April 2009 0-5