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

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.com-ps/support

ACM3P Series

Three-Phase AC Ammeters

MPM_ACM3P Series.C02 Page 3 of 6