ACM3P-4-AC1-G-C - MURATA MANUFACTURING

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.

85-264 Vac

47-63 Hz

AC/DC

CONVERTER

MICRO-

CONTROLLER

SEL

+5V

A/D

CONVERTER

L1 L2 L3

PHASE 3

PHASE 1

PHASE 2

Actual size

US E156931

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 ﬁ ts ‘0U’ & ‘1U’

rack spaces

 Low-proﬁ le surface mount design occupies minimal

behind-the-panel space

 Available in red, green, or blue LED-displays with

phase annunciators

 Low Cost; UL/CSA approvals pending

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ACM3P Series

Three-Phase AC Ammeters

MPM_ACM3P Series.A03 Page 1 of 6

Performance/Functional Speciﬁ cations

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

TECHNICAL NOTES

IMPORTANT! To ensure safe and reliable operation, ACM3P amme-

ters must be installed and serviced by qualiﬁ ed 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 ﬁ rst perform a self-test routine and then continuously display

amperes, with one of the three phase-annunciator LEDs illuminated

(L1, L2, or L3). The display will remain ﬁ xed in one of these reading

modes as long as the front panel ‘SEL’ button is not touched. Assum-

ing 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.

Conﬁ guring for 2-Phase Operation: As shipped, ACM3P ammeters

are conﬁ gured 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 fol-

lowing procedure:

A. Press and hold the SEL button for approximately ﬁ ve seconds and

then release the button once the words “LinE SEt” appear on the

display.

B. Brieﬂ y 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 ﬁ xed in the ‘2-Ph’ reading for at least ﬁ ve 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 ﬁ xed ‘3-Ph’ for at

least ﬁ ve seconds.

3. Overrange Indication: ACM3P ammeters have an overcurrent rat-

ing of 1.5 times rated current, or 150A. However, accuracy is only

guaranteed up to 100A, and the display will ﬂ ash on and off when the

current is at or above 120A.

4. Calibration: Due their digital design, ACM3P ammeters cannot be

calibrated in the ﬁ eld. ACM3P ammeters are factory-calibrated to

meet their speciﬁ ed accuracies with the factory supplied current

transformers. Use of any other current transformers will produce

signiﬁ cant errors.

Contact Murata Power Solutions if additional information is required

regarding calibration, setup, or any other technical issue pertaining to

ACM3P ammeters.

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

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 speciﬁ cations

Weight, all models 2.6 oz (74g)

Notes

➀ Speciﬁ ed 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 speciﬁ ed maximum supply currents are steady state. Larger surge currents can

occur at initial application of line power.

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ACM3P Series

Three-Phase AC Ammeters

MPM_ACM3P Series.A03 Page 2 of 6

TECHNICAL NOTES, CONTINUED

5. Wiring: All power supply and load wiring must be rated for the volt-

ages and currents they will carry and must comply with any code or

application-mandated requirements pertaining to the user’s speciﬁ c

installation.

6. Supply Fusing, and Grounding: Wires speciﬁ ed in the Functional

Speciﬁ cations section must be used for making connections to AC-

M3P 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

amperes, transformer phasing is not required. ‘Phasing’ refers to the

direction 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 speciﬁ cation 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 connection schemes could introduce signiﬁ cant mea-

surement 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. Prop-

erly 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

current 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).

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 sup-

ply 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

ammeter’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

supplied 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 modiﬁ cations.

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ACM3P Series

Three-Phase AC Ammeters

MPM_ACM3P Series.A03 Page 3 of 6

TYPICAL WIRING DIAGRAMS

TB1

PHASE A PHASE B

PHASE C

Note: Line and phase currents

are the same for Wye systems.

85–264 Vac

47–63 Hz

Fuse*

Figure 2. Wiring diagram Wye systems

Figure 3. Wiring diagram for Delta systems monitoring line current

TB1

85–264 Vac

47–63 Hz

Fuse*

PHASE A

PHASE B

PHASE C

Figure 4. Wiring diagram for Delta systems monitoring phase current

TB1

85–264 Vac

47–63 Hz

Fuse*

PHASE A

PHASE B

PHASE C

*See technical note 6.

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ACM3P Series

Three-Phase AC Ammeters

MPM_ACM3P Series.A03 Page 4 of 6

MECHANICAL SPECIFICATIONS

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)

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

TB1

Lead Length

5.0 (127) min.

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 speciﬁ ed):

.XX ± 0.02 (0.51)

.XXX ± 0.010 (0.254)

Angles ± 2˚

Components are shown for reference only.

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ACM3P Series

Three-Phase AC Ammeters

MPM_ACM3P Series.A03 Page 5 of 6

NOTES

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. Speciﬁ cations are subject to change without

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Murata Power Solutions, Inc.

11 Cabot Boulevard, Mansﬁ eld, MA 02048-1151 U.S.A.

ISO 9001 and 14001 REGISTERED

ACM3P Series

Three-Phase AC Ammeters

MPM_ACM3P Series.A03 Page 6 of 6