SIMPLIFIED SCHEMATIC DIAGRAM
PRODUCT OVERVIEW
Murata Power Solutions’ ACM3P series 3-phase AC ammeters measure and display the
true-rms values of 2- or 3-phase ac mains current. A front panel touch switch enables the
selection of a continuous reading of any of the three phases. All ACM3P ammeters are func-
tionally complete, with built-in L1, L2, and L3 current transformers—no other user-supplied
components or hardware are required.
ACM3P series AC ammeters are available with a 0-100A input range (150A peaks) and
provide a resolution of 0.1 Amp. Their 85-264Vac (47-63Hz) operating supply range makes
these ammeters perfect for worldwide 3-phase current monitoring applications. And, unlike
conventional average-responding products, ACM3P ammeters can accurately display the
true-rms values of triangle waves, square waves, and other irregularly shaped AC current
waveforms, with an accuracy of ±2% of full scale.
Their large (0.36"/9.2mm), bright LED display, available in a choice of red, blue, or green,
enables ACM3P ammeters to be easily readable from as far as 15 feet (5 meters). All
units are packaged in a one-piece, vibration resistant, polycarbonate housing that can be
installed in vertical ‘0U’ or horizontal ‘1U’ rack spaces. Their miniature size is ideal for UPS
backup power sources, power strips, alternative energy metering, and any other applica-
tions that require precise monitoring of 2- or 3-phase ac current.
A
B
85-264 Vac
47-63 Hz
AC/DC
CONVERTER
MICRO-
CONTROLLER
SEL
+5V
+5V
+5V
A/D
CONVERTER
L1 L2 L3
PHASE 3
L3
PHASE 1
L1
PHASE 2
L2
CURRENT
LIMITED
SUPPLY
Actual size
FEATURES
Measure and display the true-rms current of 3-phase
power systems
Universal 85-264Vac (47-63Hz) operating supply
range
Three built-in current transformers measure up to
100A per phase
Ideal for power distribution units (PDUs) and backup
power systems
Low power consumption: less than ¼watt from
120Vac supply
One-piece polycarbonate housing fits ‘0U’ & ‘1U’
rack spaces
Low-profile surface mount design occupies minimal
behind-the-panel space
Available in red, green, or blue LED-displays with
phase annunciators
Low Cost; approvals to UL/cUL/IEC/61010-1
C
®
US E156931
www.murata-ps.com
www.murata-ps.com/support
For full details go to
www.murata-ps.com/rohs
ACM3P Series
Three-Phase AC Ammeters
MPM_ACM3P Series.C01 Page 1 of 6
Performance/Functional Specifications
Typical at TA=+ 25ºC, 120Vac @ 50Hz, unless otherwise noted
ORDERING INFORMATION
ACM3P-4-AC1-R-C 100A, 85-264Vac Supply, Red LED Display
ACM3P-4-AC1-G-C 100A, 85-264Vac Supply, Green LED Display
ACM3P-4-AC1-B-C 100A, 85-264Vac Supply, Blue LED Display
ACM3P-4-AC1-B-28-C 100A, 85-264Vac Supply, Blue LED Display,
28 inch lead length
TECHNICAL NOTES
IMPORTANT! To ensure safe and reliable operation, ACM3P amme-
ters must be installed and serviced by qualified technical personnel.
Contact Murata Power Solutions if there is any doubt regarding their
installation or operation.
1. Measurement Type: ACM3P series 3-phase ammeters employ a
precision energy metering integrated circuit and a low-power micro-
controller to measure and display the rms value of 2- or 3-phase
ac-mains current. However, while the unit has an upper bandwidth
of 14kHz, dc components or frequencies below 47Hz will not be
measured accurately.
2. Basic Operation: Upon application of ac power to TB1, the unit will
first perform a self-test routine and then continuously display am-
peres, with one of the three phase-annunciator LEDs illuminated (L1,
L2, or L3). The display will remain fixed in one of these reading modes
as long as the front panel ‘SEL’ button is not touched. Assuming phase
L1 is initially illuminated, momentarily touching the ‘SEL’ button two
times in succession will cycle the display to phase L2, and then to
phase L3. Momentarily touching ‘SEL’ a third time will return the unit
back to displaying phase L1 current.
If power is removed and then restored, the ACM3P will perform a
self-test and then return to displaying the last selected phase, i.e., the
phase it displayed just before power was removed.
Configuring for 2-Phase Operation: As shipped, ACM3P ammeters
are configured to measure and display 3-phase currents (L1, L2, and
L3 current transformers are all active). The unit can be set to display
2-phase currents (only L1 and L2 are active) by performing the follow-
ing procedure:
A. Press and hold the SEL button for approximately five seconds and
then release the button once the words “LinE SEt” appear on the
display.
B. Briefly tapping the SEL button will alternate the display reading
between ‘2-Ph’ and ‘3-Ph’ each time SEL is tapped.
C. To change the factory default 3-phase mode to 2-phase, leave the
display fixed in the ‘2-Ph’ reading for at least five seconds.
To revert the unit back to 3-phase operation simply repeat the above
procedure but, in step C, allow the unit to display a fixed ‘3-Ph’ for at
least five seconds.
ACM3P ammeters with manufacturing date codes of June 2016 or
later have the additional ability to continuously scroll (“auto-scroll”)
through all 3 phases, or auto-scroll through only 2 phases.
The process for configuring the ACM3P for auto-scrolling operation
begins by first holding down the ‘SEL’ switch for five seconds to enter
the programming mode that is indicated by the display showing “LinE
SEt.”
After the unit displays “LinE SEt,” immediately and repeatedly
pressing and releasing the SEL switch will cycle the unit through the
following four operating-mode options:
!
Measurement Limits Min. Typ. Max. Units
AC (rms) Current, L1, L2, L3 ➀0.0 — 100.0 Amperes
Overcurrent Rating ➁1.5 x Rated full-scale current
Performance
Sampling Rate 1.5 samples/sec
Current Accuracy ➂±2% ±3%
Measurement Bandwidth (L1, L2, L3) 14kHz
Temperature Drift (0 to 60ºC) 0.5 Counts/ºC
Zero-Current Reading (within 1 sec.) 1 Counts
UL/IEC61010-1 Measurement category II
Supply Voltage (TB1)
All Models 85 120 264 Vac/47-63Hz
Supply Current ➃
ACM3P-X-AC1-R-X-C 35 50 110 mA
ACM3P-X-AC1-G-X-C 50 75 165 mA
ACM3P-X-AC1-B-X-C 50 75 165 mA
Power Supply Terminal Block (TB1)
Wire Size 16-22AWG, solid or stranded
Insulation Strip Length 6.4mm (0.250 in)
Screw Tightening Torque 0.4Nm (3.6 lb-in)
Rated Voltage 300Vac
Display
Display Type and Size 4 Digit LED, 9.14mm (0.36in) high
Overrange Indication Flashing display
Decimal Point Selection Automatically Set
Physical/Environmental
Operating Temperature: 0 — +60 ºC
Storage Temperature: -40 — +75 ºC
Humidity (non-condensing): 0 — 85 %
Dimensions: See mechanical specifications
Weight, all models 2.6 oz (74g)
Notes
➀ Specified full-scale currents are those passing through the power meter’s built-in current
transformer’s primary load-circuit. See Notes 2 and 3 below for additional information.
➁ The overcurrent rating of 1.5 x the rated full-scale current is a continuous rating and applies to
the current passing through the built in current transformer. Accuracy is guaranteed up to the
rated current level.
➂ Power Meters are calibrated with near full-scale 50Hz sine-wave inputs.
➃ All specified maximum supply currents are steady state. Larger surge currents can occur at
initial application of line power.
continued on next page
www.murata-ps.com/support
ACM3P Series
Three-Phase AC Ammeters
MPM_ACM3P Series.C01 Page 2 of 6
2P-A > 3P-A > 2P > 3P
Where:
2P-A enables continuous auto-scrolling 2-phase operation
3P-A enables continuous auto-scrolling 3-phase operation
2P enables fixed 2-phase operation
3P enables fixed 3-phase operation
To enable the desired mode of operation, simply stop pressing the SEL
switch after the desired mode is displayed. The unit will begin normal
operation in the selected mode five seconds after the last SEL switch
activation.
3. Overrange Indication: ACM3P ammeters have an overcurrent rating of
1.5 times rated current, or 150A. However, accuracy is only guaranteed
up to 100A, and the display will flash on and off when the current is at or
above 120A.
4. Calibration: Due their digital design, ACM3P ammeters cannot be cali-
brated in the field. ACM3P ammeters are factory-calibrated to meet their
specified accuracies with the factory supplied current transformers. Use
of any other current transformers will produce significant errors.
Contact Murata Power Solutions if additional information is required
regarding calibration, setup, or any other technical issue pertaining to
ACM3P ammeters.
5. Wiring: All power supply and load wiring must be rated for the voltages
and currents they will carry and must comply with any code or applica-
tion-mandated requirements pertaining to the user’s specific installation.
6. Supply Fusing, and Grounding: Wires specified in the Functional
Specifications section must be used for making connections to ACM3P
series ammeters’ TB1 terminal block. No connection is required for earth/
chassis ground.
ACM3P series ammeters are not internally fused. Terminal block TB1 is to
be used only for powering the ammeter's internal circuitry; it must not be
used to supply power to external loads. The supply wires feeding these
power meters must be fused with a 0.5A/250V time delay/time lag fuse,
in accordance with applicable regulatory codes.
Wire insulation must be stripped to within ±10% of the stated dimen-
sions, and wires should be inserted into TB1 such that their insulation is
not pinched by the screw terminal.
7. Current Transformer Phasing: Since the ACM3P only measures am-
peres, transformer phasing is not required. ‘Phasing’ refers to the direc-
tion of the current-carrying wire as it passes through the primary hole of
each of the three built-in current transformers.
8. Connector Torque Ratings: It is important to tighten TB1’s screw-
terminals to their rated torque specification of 3.6 pound-inches (0.4Nm).
Proper tightening will minimize connector losses and ensure safe, reliable
operation.
9. Isolation: Except for the 2-56 thread metallic mounting studs, all of the
ACM3P ammeter’s internal components (printed circuit board, resistor,
capacitors, current transformers L1, L2 and L3’s secondary leads, etc.)
are at the ac-mains potential connected to TB1. ACM3P ammeters are
designed to be powered from one ac power-source only. Any other con-
nection schemes could introduce significant measurement errors.
The three built-in current transformers have a dielectric breakdown
rating of 2kV minimum, allowing them to safely monitor 480V, 3-phase
ac mains currents. This dielectric rating pertains only to the insulated
load-carrying wire as it passes through the built-in CT’s primary hole.
However, attention must still be paid to ensure adequate wire-to-wire
spacings, and wire-to-metallic surface spacings. Properly rated wiring
and fusing must be used for all installations, as noted in Technical Notes
5 and 6 above.
IMPORTANT: Even though ACM3P ac ammeters can be used in 480V cur-
rent monitoring applications, the ac supply connected to TB1 must never
exceed the maximum rating of 264V/47-63Hz.
Figure 1. Panel Installation
SIDE VIEW
2-56 Hex Nuts (4 places)
Tighten each nut to 15 to 20
ozf-in (0.106 to 0.140 N-m).
L1
L2
L3
ACM3P
Panel Cutout
PANEL
PANEL INSTALLATION
All connections to ACM3P ammeters must be made after the unit is
securely attached to the panel, and with all associated load and supply
voltages de-energized (off), using extreme caution and observing all
safety measures applicable to the user’s installation.
Care should be exercised when passing conductors through the am-
meter’s built-in current transformers L1, L2, and L3. The installed wire-
positions should be such that minimal mechanical forces are applied
to the current transformers, TB1, or to the ACM3P ammeter itself. In high-
vibration environments, it is strongly recommended that strain reliefs be
used for all wiring.
Using Figure 1 as a guide, carefully insert the ACM3P assembly into the
panel opening. From the rear of the panel, install and then tighten the
four #2-56 hex nuts over the threaded studs. Tighten each nut to 15 to
20 ozf-in (0.106 to 0.140 N-m). Use only the factory-supplied hardware
as the use of substitute hardware could result in an unsafe installation
and/or adversely affect the reliability of the installation.
The recommended panel thickness range that can be used with the sup-
plied hardware is 0.040 inches (1.0mm) to 0.25 inches (6.4mm). Panel
thicknesses outside of this range may require additional user-supplied
hardware or modifications.
www.murata-ps.com/support
ACM3P Series
Three-Phase AC Ammeters
MPM_ACM3P Series.C01 Page 3 of 6
TYPICAL WIRING DIAGRAMS
B
A
TB1
PHASE A PHASE B
L1
L1
L2
L3
PHASE C
Note: Line and phase currents
are the same for Wye systems.
L2
L3
85–264 Vac
47–63 Hz
Fuse*
Figure 2. Wiring diagram Wye systems
Figure 3. Wiring diagram for Delta systems monitoring line current
B
A
TB1
85–264 Vac
47–63 Hz
Fuse*
PHASE A
PHASE B
L1
L1
L2
L3
PHASE C
L2
L3
Figure 4. Wiring diagram for Delta systems monitoring phase current
B
A
TB1
85–264 Vac
47–63 Hz
Fuse*
PHASE A
PHASE B
L1
L1
L2
L3
PHASE C
L2
L3
*See technical note 6.
*See technical note 6.
*See technical note 6.
www.murata-ps.com/support
ACM3P Series
Three-Phase AC Ammeters
MPM_ACM3P Series.C01 Page 4 of 6
MECHANICAL SPECIFICATIONS
L1
MULTI-PHASE AC AMMETER
L2 L3
SEL
1.43
(36.3)
2.10 (53.3)
Front View
Back View
0.51
(12.95)
1.07
(27.20)
0.40
(10.16)
0.12 (3.05) (min)
0.12 (3.05) (min)
Side View
1.63
(41.4)
0.086 DIA (REF)
2-56 UNC THREAD
0.33 (8.39)
(min)
0.22 (5.59)
(min)
0.60
(15.24)
(max)
Bottom View
B
A
TB1
CT Lead Length:
Standard: 5.0” (127mm) min.
Optional: 28.0” (700mm) min. on blue LED model
L3
L2
L1
Diameter:
Inner: 0.57 (14.5)
Outer: 1.175 (29.8)
PANEL CUTOUT
RECOMMENDED DRILL AND PANEL CUTOUT DIMENSIONS
INTERNAL CORNER RADII:
0.032 (0.81) MAX.
1.07
(27.18)
0.870
(22.10)
1.426
(36.22)
1.626 (41.30)
0.093 (2.362) DIAMETER (4 REQUIRED)
The panel opening must be centered vertically and
horizontally between the four 0.093 (2.362mm)
diameter holes.
Dimensions are in inches (mm).
Tolerances (unless otherwise specified):
.XX ± 0.02 (0.51)
.XXX ± 0.010 (0.254)
Angles ± 2˚
Components are shown for reference only.
www.murata-ps.com/support
ACM3P Series
Three-Phase AC Ammeters
MPM_ACM3P Series.C01 Page 5 of 6
NOTES
1. Description of safety marks:
Caution, risk of electrical shock
Caution, risk of danger
Equipment is protected throughout by double or reinforced insulation
2. Cleaning Instructions: Gently clean with dry cloth only.
3. Caution: if the equipment is used in a manner not specified by Murata Power Solutions, the protection provided by the equipment may be impaired.
www.murata-ps.com/support
Murata Power Solutions, Inc. makes no representation that the use of its products in the circuits described herein, or the use of other
technical information contained herein, will not infringe upon existing or future patent rights. The descriptions contained herein do not imply
the granting of licenses to make, use, or sell equipment constructed in accordance therewith. Specifications are subject to change without
notice. © 2017 Murata Power Solutions, Inc.
Murata Power Solutions, Inc.
11 Cabot Boulevard, Mansfield, MA 02048-1151 U.S.A.
ISO 9001 and 14001 REGISTERED
This product is subject to the following operating requirements
and the Life and Safety Critical Application Sales Policy:
Refer to: http://www.murata-ps.com/requirements/
ACM3P Series
Three-Phase AC Ammeters
MPM_ACM3P Series.C01 Page 6 of 6
