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Technical
Section 11
Dimensions
Section 12
7
CT,
Ip/5A ratio
Current
transformers
The Ip/5A ratio current transformer delivers at the secondary a current (Is) of 0 to 5 A
that is proportional to the current measured at the primary (Ip).
This allows them to be used in combination with measurement equipment:
b
b
ammeters
b
b
kilowatt-hour meters
b
b
measurement units
b
b
control relays
b
b
etc.
When the primary is energized, the measurement equipment nearly acts as a short
circuit which keeps the secondary voltage very low. This voltage will increases
significantly if the short circuit is removed.
CT selection - conductor rating aspects
The choice depends on the conductor profile and the maximum intensity
of the primary circuit.
CT with let-through primary
Conductor type Cable
Mixed, bars or cables
Vertical or horizontal bars
Vertical bars
Suggested
Current
Transformer
and mounting
DB415986.eps
DB415920.eps
DB415988.eps
DB415989.eps
DB415921.eps
DB415987.eps
Ratings (A)
40 to 250
150 to 800
200 to 4000
500 to 600
5000 to 6000
CT internal
profile
Type C
Type M
Type D
(1)
Type V
MA
MB
MC
VF
VV
MD
ME
MF
(1)
Two secondary connectors (parallel internal wiring - only one secondary winding) for easier
cable access. 1 lateral + 1 on one extremity. Warning: only one must be used at a time.
Specific mounting: use of cylinder
A cylindrical metallic spacer ensures a proper CT positioning when the conductor or
the CT cannot be positioned perpendicular. Secured by bolt + nut.
CT with primary connection by screw and nut
(example: use of cylinder with bar or cable)
DB416006.eps
DB416005.eps
16550 (brass)
METSECT5CYL1 (aluminium)
Ip
Is
Primary
circuit
Secondary
circuit
N
Ph
Measurement
equipment
Load
DB416186.eps
Application diagram of a CT.