Description and control
Description and control
The SIERS electrical racking system is
powered by 125 Vdc or (optionally) by
120 Vac power from the controller. Typically,
ac power is obtained from a control power
transformer (CPT) in the controller, or from
the user’s external source. However, power
from the controller CPT is not available
when the equipment is de-energized. For
this reason, it is preferred that a dc source
(125 Vdc) be used to power the SIERS
electrical racking system, as this power will
normally be available even when the
equipment itself is de-energized. Control
power requirements are detailed in Table 1.
In the event a dc source is not available and
ac power is not available, the isolating
switch can be operated manually, following
the normal procedures given in the relevant
instruction manual.
If control power is provided from a
controller CPT, the wiring to the power
supply for the racking system will be
installed in the controller at the factory.
Option: external ac supply for
maintenance
If 120 Vac control power is obtained from a
remote source, such as a wall outlet in the
vicinity of the controller or from a portable
generator, the control power connection
should be made to the control power socket
installed in the controller as shown in Figure
2: Flanged inlet type 5-15P (on right) for
connection to external 120 Vac power
source extension cord receptacle type 5-15R
(on left). The receptacle (socket with male
pins) is a NEMA standard type 5-15P
recessed socket (referred to as a flanged
inlet in NEMA standard WD6) for use with a
NEMA standard 5-15R female receptacle,
three wire with ground.
The SIERS electrical racking system controls
are located in a self-contained enclosure on
the top of each controller section (Figure 4:
Control devices for SIERS racking system).
The SIERS electrical racking system circuit
includes miniature circuit breaker protection
for both the 125 Vdc and 120 Vac supplies (if
applicable), and fuse protection for the
motor (FU2) supply circuit and the 24 Vdc
power supply circuit (FU1), as well as for the
24 Vdc supply (FU3) to the current switch,
logic module, and digital module.
The fuse in the motor circuit has time-delay
characteristics to avoid fuse operation on
motor inrush current.
The SIERS system is controlled using a
Siemens LOGO! programmable logic module
(LM) with digital expansion module (DM)
with auxiliary relays for motor control. The
LM receives input from limit switches on the
racking mechanism that signal the isolating
switch position (OPEN/DISCONNECT or
CLOSE/CONNECT). The limit switches also
illuminate the light-emitting diode (LED)
pushbuttons on the control pendant, which
indicate the isolating switch position. A solid
green LED indicates OPEN/DISCONNECT
position and solid red LED indicates CLOSE/
CONNECT position.
A blinking LED indicates the position
towards which the isolating switch is
moving.
The LM responds to commands from the
pushbuttons on the control pendant to
move the isolating switch between
positions.
The system includes current sensing to
respond to excessive current in the motor
circuit. Excessive current indicates a motor
overload, whether due to a jam or
otherwise. When the overcurrent is
detected, the LM initiates alarm indication
on the amber LED on the hand-held control
pendant, and stops the racking process.
After a time period of five seconds, the LM
restarts the racking process to move the
isolating switch to OPEN/DISCONNECT
position.
If this is unsuccessful, a second attempt to
rack to the OPEN/DISCONNECT position is
initiated after a time period of five seconds.
If the second attempt is also unsuccessful,
the LM disables electrical function, and the
user must use the manual procedure to
operate the isolating switch to the OPEN/
DISCONNECT position.
Figure 2: Flanged inlet type 5-15P
(on right) for connection to
external 120 Vac power source
extension cord receptacle type
5-15R (on left) (optional)
Voltage
I (nominal) A
I (maximum) A
Racking time s
125 Vdc
0.9
1.6
< 2
120 Vac
0.9
1.6
< 2
Table 1: Control power requirements
6
SIERS Siemens Integrated Electrical Racking System |
Instruction manual