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. If the
auxiliary is separate the measuring range of the voltage
input is 10-120%.
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
Internally the M560 has current transformers fitted which are
either 5 Amp or 1 Amp. The current circuit is designed for
connection to the secondary of external current
transformers. 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 side of the M560. e.g. If the M560 has a current
ratio specified as 500/5A, then the current transformer could
be changed to 800/5A (or any ratio with secondary 5A) and
used once the current ratio has been programmed into the
M560, (see section 4.2.2.) But if the ratio change was 800/1A
the M560 would have to be returned to the factory to have the
internal current transformer changed to 1 amp.
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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