ACA5-20RM Datasheet, PDF (3/5 Pages) Murata Power Solutions Inc. – True-rms-AC Ammeters with 5A CT Inputs

ACA5-20RM Series
True-rms-AC Ammeters with 5A CT Inputs
3. Wire Gauges and Fusing: Wires specified in the Functional Specifica-
tions section must be used for making connections to ACA5-20RM
Series ammeters. All power-supply and load wiring must be rated for
the supply voltages and currents they will conduct and must comply
with any code or application-mandated requirements pertaining to the
user’s specific installation.
The supply wires connected to both the ammeter and the load must
be fused according to the current rating of the wire gauge being used,
in accordance with applicable regulatory codes. Also, wire insula-
tion should be stripped to within +/–10% of the stated dimensions,
and wires should be inserted into TB1 such that their insulation is not
pinched by the screw terminal. TB1 is to be used only for powering the
meter’s internal circuitry; It must not be used to supply current to any
external loads.
All models draw minimal steady-state supply currents (50mA max.),
and in most applications they can be fused according to the supply
wire’s maximum amperage rating. However, these models can draw
significantly higher surge currents for brief periods when the ac line
voltage is initially applied.
4. AC Supply Polarity and Grounding: The two supply inputs, TB1-A and
TB1-B, on ACA5-20RM ammeters are not in themselves polarity sensi-
tive, that is, they have no internal “AC LO” or “AC HI” designations.
ACA5-20RM ammeters do not include or require a connection to earth/
chassis ground.
5. Connector Torque Ratings: It is important to tighten TB1’s, screw-ter-
minals to their rated torque specification of 3.6 pound-inches (0.4Nm).
Proper tightening will minimize connector losses and ensure safe,
reliable operation.
A
FUSED AC POWER
B
6. Isolation: The built-in toroid sensor (L1) provides a minimum of
2000Vdc isolation between the external CT’s 5A secondary conduc-
tors and the ammeter supply voltage connected to TB1.
7. CT Precautions: In normal operation, a 5A CT’s secondary circuit
operates at a very low voltage due to its closed-loop operation and
low burden resistance. However, a CT can still generate potentially
lethal voltages if its output current is suddenly interrupted. For
example, loose 5A CT secondary connections can cause a condition
referred to as “inductive kick”. Inductive kick can generate extremely
high voltages across a CT’s intermittent secondary connections.
Therefore, implementing connections to any 5A current transformer’s
output leads must only be performed with zero load-current flowing
the CT’s primary load-circuit.
8. CT Connections and Grounding: Some applications require connect-
ing one of the external 5A CT’s output leads to earth/chassis ground.
In the USA, consult the latest revision of the National Electrical Code
(NEC) for more information regarding CT grounding.
After all mechanical assembly is completed, connect the two output
leads of the external 5A CT to each other after they are run through
L1’s center hole. Pressure-style connectors (commonly referred to as
“wire nuts”) are acceptable as long as they are rated for the number
of conductors and voltage involved.
9. Replacing Analog Panel Meters: ACA5-20RM ammeters can be
used as direct replacements for most analog panel meters driven by
external 5A CT’s. All wiring operations must be performed with both
the load and the supply power sources completely de-energized.
BACK VIEW
TB1
L1
Figure 2. Typical wiring diagram
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MPM_ACA5-20RM.A01 Page 3 of 5