Functional Description; Overview - Siemens SWT 3000 Equipment Manual

Power Supply

13.1 Functional Description

13.1 Functional Description

Overview

13.1.1
The input voltage is fed to the input capacitor via a fuse, an input filter, and an inrush current limiting
element. This capacitor supplies the switching transistor of the single-ended converter. Each output is
supplied from a separate winding. The secondary voltage is rectified. The output voltage ripple is minimized
with a storage choke and subsequent output filter.
Control Circuit
The control circuit monitors the output voltage Uout1. It also generates the control signal for the switching
transistor on the primary side taking into account the maximum permissible output currents. The control
signal is fed back to the switching transistor via a transformer for electrical isolation. The secondary outputs
Uout2 and Uout3 are controlled individually and independently and each have their own current limiting
system. If one of the secondary outputs is operating in current limiting mode, the voltages of the other
outputs are also reduced.
Fuse
A fuse holder mounted on the rear of the unit holds a 5 x 20-mm fuse, which protects the unit against major
damage. For input voltages ≥ 200 V, an external fuse or a protection switch at system level is recommended
additionally.
!
CAUTION
If the right fuse is not used, the device can not work properly.
If you do not comply with the safety notes, this will result in death, severe injury, or considerable
material damage.
Use only fuses with suitable ratings (see chapter Technical Data).
²
NOTE
i
i
Always use following fuse: 6.3 AT DC 400 V/AC 500 V rated. Siemens recommends the fuse 047706.3MXP
from the company Littlefuse to be inserted the original power supply.
Disconnection
An internal inhibit signal disconnects the outputs as follows:
•
Auxiliary voltage below 0.8 x U
•
Auxiliary voltage above 1.1 x U
Inrush Current
When switching on for the first time, an NTC thermistor in the input circuit reduces the inrush current surge by
a factor of about 5 to 10. This reduction protects connector junctions and switches against possible damage.
Repeated start-up operations at short intervals reduce the effect of the NTC with the result that the inrush
current surge increases.
Inhibit Input
The inhibit input enables the output voltages to be switched on and off with logic signal Uinh (TTL, CMOS).
The inhibit input (Number 2) must be connected to the minus pole of output 1 (Number 23) in order to enable
360
min
max
Smart Communication, SWT 3000 Teleprotection, Equipment Manual
C53000-G6040-C605-1, Edition 03.2020