Siemens TC12 Installation, Commissioning And Maintenance Handbook page 91

maximum loads when a 50-0-50 V RMS mains supply is used. The limits are only
reduced if the actual voltage being monitored is at the lower level, i.e. if a 50-0-50
V RMS supply (derived from a transformer) is used but the monitoring is on the
240 V RMS side of the transformer, then the limits do not need to be reduced.
If the nominal load current (including red/ambers) of a particular controller
output exceeds 4.0 A RMS, at nominal mains voltage, then that output
should be split and treated as two separate outputs (although the same
voltage sensor can be used for both).
For example, 8 pedestrian plus 8 wait indicator.
For example, 8 vehicle plus 4 pedestrian plus 4 wait indicator.
The limit of 8 applies if they are all vehicle signals. For fewer than 8 vehicles the
limit is greater, i.e. 6 vehicle plus 2 pedestrian plus 2 wait indicator.
To allow monitoring of tube type signs at 50-0-50 V sites, the signs must be driven
with the 50-0-50 V supply and the tubes must have the standard voltage-current
characteristic.
CAUTION The current sensors may produce a high voltage, when not
terminated into the OTU board, if current is passed through the core.
The Current transformers measure the current flowing in conductors that are
passed through their core. To maintain the correct relationship between the
current flowing in the conductors and the output from the sensor, the sensors must
be connected the correct way round.
The current transformers are toroidal and one side is marked with a red spot to
indicate the input direction. The Live conductor(s) should pass from the controller
output terminal(s) through the centre of the current transformer, entering the side
with the red spot marker, and on to the lamp(s).
The output wires from the current transformer are red (positive) and white
(negative) and are terminated with Berg mini PV terminals which are clipped into a
Berg mini latch housing to provide a complete sensor assembly which plugs into
PL1 on the OTU board. Referring to Figure 35, the red wire connects to the
required number LMU input shown with a +, and the white wire connects to the
corresponding - input. Inputs should normally be allocated consecutively starting
from number 1. The current sensors should then be anchored by passing a
TYWRAP or equivalent through the sensor hole and around a suitable fixing point.
Up to 23 current transformers can be used per Outstation when equipped with
LMU facilities.
666/HE/43100/000
TC12 Installation, Commissioning & Maintenance Handbook
Page 81 Issue 10