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3.5
Wiring the Measurement Circuit when Using
External PT/CT
WARNING
CAUTION
Wiring diagram for single-phase, two-wire system with PT and CT connected
(253401, 253502, 253503)
Wiring diagram for single-phase, three-wire system with PT and CT connected
(253502, 253503)
IM 253401-01E
• When using an external CT, do not allow the secondary side of the CT to
go open-circuit while power is supplied, otherwise an extremely high
voltage will be generated on the secondary side of the CT.
• A load current flows in the thick lines shown in the diagrams; therefore, a
wire with sufficient current capacity must be used for these lines.
Use of a PT (or CT) enables measurement of voltage or current even if the maximum voltage or
maximum current of the object to be measured exceeds the maximum measuring range.
• If the maximum voltage of the object to be measured exceeds 600V, connect an external
potential transformer (PT), and connect the secondary side of the PT to the voltage input
terminals.
• If the maximum current of the object to be measured exceeds 20A, connect an external
current transformer (CT), and connect the secondary side of the CT to the current input
terminals.
SOURCE
LOAD
L CT
V
l
V
±
A
±
Input terminal
(ELEMENT)
SOURCE
N
CT
L
l
V
±
A
±
Input terminal
(ELEMENT1)
Note
• Using the scaling function enables direct reading of measured values on the display. Refer to section 4.4
on page 4-6.
• It must be noted that measured values are affected by the frequency and phase characteristics of PT and
CT.
SOURCE
PT
L CT
v
l
V
±
A
±
Input terminal
(ELEMENT)
PT
CT
V
L
v
l
V
±
A
±
Input terminal
(ELEMENT3)
LOAD
V
PT
v
LOAD
PT
V
v
3-7
3
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