Low Inrush Transformer; High Power Unit (Hpu) - Siemens ST950 Handbook

4.1.2

Low Inrush Transformer:

Siemens have developed a low inrush transformer that allows lower rating
protection devices to be used, as shown below: -
Controller MCB changed from 20A type D MCB to 6A type D MCB,
Master Fuse changed from 30A to 16A
Electricity Cut-out fuse changed from 45A to 25A.
The lower rating Electricity Cut-out fuse encourages the Electricity Supplier to
provide power without supply metering.
The low inrush transformers are available in 20A only controller cabinets; see the
appendix for Part Numbers.
4.2

High Power Unit (HPU)

The HPU distributes the 48V lamp supply and low voltage logic supply from the
Lamp Supply transformer to three LSLS cards. It has monitor circuitry and
terminations for the connection of up to eight 48V regulatory signs, provides
connections for the Solar Cell and 24V Loop Detector/above ground detector supply
and incorporates the Dim/Bright, A and B relays. If the total lamp load exceeds 20A
or more then three LSLS cards are required, see section 4.3.
The HPU provides the following outputs:
Supply
Lamp Supply
(Bright)
(Dim)
Regulatory Supply
LSLS#1 Logic Supply
LSLS#2 Logic Supply
LSLS#3 Logic Supply
Loop Detector Supply
Security classification
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Last Editor
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Copyright © Siemens plc 2020. All Rights Reserved.
A low inrush transformer weighs about 20kg. In the very unlikely
event of a transformer failing, appropriate lifting techniques MUST be
used, and leather rigger gloves are recommended.
Voltage (nominal)
0V (Earthed)
-48V DC rms nominal
-27.5V DC rms nominal
0V (Earthed)
-48V DC rms nominal
12.2V AC rms
12.2V AC rms
12.2V AC rms
0V (Earthed)
-24V DC rms nominal
Table 2 – HPU Outputs
Unrestricted
7
manpreet.jeerh
ST950 ICM Handbook
Mobility, Intelligent Traffic Systems
Sopers Lane, Poole, Dorset, BH17 7ER
Measures as:
(See Note 1)
0V
-44.6V DC
-25.4V DC
0V
-44.6V DC
12.2V AC
12.2V AC
12.2V AC
0V
-20.9V DC
Page
Status
Date
Document No.
Mobility is a division of Siemens Plc
Connector
PL4/6/7/ pins 1,2,3
PL4/6/7 pins 4.5.6
SK1 pins 1a, 2a, 3a,
4a, 5a, 6a, 7a, 8a
SK1 pins 1b, 2b, 3b,
4b, 5b, 6b, 7b, 8b
PL4 pins 7 and 8
PL6 pins 7 and 8
PL7 pins 7 and 8
SK2 3a
SK2 3b
29 of 154
Issued
January 2020
667/HE/45950/000