Schneider Electric PM5100 Control power wiring, Communications, Balanced system considerations

PowerLogic™ PM5100 series user guide Chapter 3—Hardware Reference

Balanced system considerations

In situations where you are monitoring a balanced 3-phase load, you may choose to connect only one or two CTs on the phase(s) you want to measure, and then configure the meter so it calculates the current on the unconnected current input(s).

NOTE: For a balanced 4-wire Wye system, the meter’s calculations assume that there is no current flowing through the neutral conductor.

Balanced 3-phase Wye system with 2 CTs

The current for the unconnected current input is calculated so that the vector sum for all three phase currents equal zero.

Balanced 3-phase Wye or Delta system with 1 CT

The currents for the unconnected current inputs are calculated so that their magnitude and phase angle are identical and equally distributed, and the vector sum for all three phase currents equal zero.

NOTE: You must always use 3 CTs for 3-phase 4-wire center-tapped Delta or center-tapped open Delta systems.

Control power wiring

For wiring instructions and safety precautions, see the meter installation sheet that was shipped with your meter, or download a copy at www.schneider-electric.com.

The meter can be powered from an AC or DC power source.

•L1 and L2 are non-polarized. If using an AC power supply with neutral, connect neutral to the meter’s L2 terminal.

•Always use a fuse on L1. Fuse L2 when connecting an ungrounded neutral to the control power.

•If using a control power transformer, fuse both primary and secondary sides of the transformer.

•The fuses / circuit breakers must be rated for the installation voltage and sized for the available fault current.

Communications

This section provides additional information about the communications ports and topologies supported by the meter. You must wire and configure the RS-485 port in order to communicate with the meter.

Serial communications

The meter supports serial communications through the RS-485 port. Up to 32 devices can be connected on a single RS-485 bus.

In an RS-485 network, there is one master device, typically an Ethernet to RS-485 gateway. It provides the means for RS-485 communications with multiple slave devices (for example, meters). For applications that require only one dedicated computer to communicate with the slave devices, an RS-232 to RS-485 converter can be used as the master device.

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