User Manual Chapter 2
GFK-2749A Jan 2020
Installation 29
Configuration for Three-Wire Delta system with Two PTs
(Two Wattmeter Method) for Load Monitoring
The systems detailed below show two PTs being used in an open delta configuration
connected to the Terminal Assembly. The PSM module can be configured for either B phase
common, or C phase common. In this mode (selected through the configuration
parameters) the line to line voltage is typically scaled down to the level of 120VAC nominal.
The third voltage and current are reconstructed from the other two by the PSM.
The reconstructed signals must be configured as not used. All additional scaling factors
must be applied to the values being returned by the PSM by the host controller logic
program.
For safety considerations, both the primaries and secondaries of the potential transformers
must be fused. A fuse failure is an indication of wiring problems within the system. Note that
in this configuration, the phasing of the potential transformers is slightly different.
Figure 14
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