Multitek MultiLed M812-LD Series Operating Manual page 62

6.2 Auxiliary Supply
The auxiliary supply can be connected in parallel with the measuring
input voltage, but this restricts the measuring range of the input
voltage to ± 15% of nominal.
6.3 Protective Fuses
It is good practice for the user to provide fuse protection to all input
circuits and the auxiliary supply.
6.4 Current Transformers (C.T.s)
Internally the MultiLed has C.T.s fitted which are either 5A or 1A.
The current circuit is designed for connection to the secondary of
external C.T. These transformers should conform to at least Class 1
as per BS7626 (IEC 185) or equivalent. The secondary of these
external transformers must have the same nominal current input as
that specified on the data label on the MultiLed. e.g. If the
MultiLed has a current ratio specified as 500/5A, then the CT could
be changed to 800/5A (or any ratio with secondary 5A) and used
once the current ratio has been programmed into the MultiLed.
But if the ratio change was 800/1A the MultiLed would have to be
returned to the factory to have the internal current transformer
changed to 1A.
Warning. The secondary of a current transformer must never be
allowed to be in an open circuit condition when the primary is
energized. In the open circuit condition high voltage may be
present. Each current transformer secondary should be short-
circuited when not connected to the meter.
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