2-1
IM WT1801-01EN
2 Fundamental Measurement Conditions
Wiring System Settings (WIRING)
The wiring system settings are listed below.
•
•
Efficiency equation (η Formula
•
Independent input element configuration (Element Independent)
•
Delta computation (Δ Measure; option
Wiring System (Wiring)
There are five wiring systems available on the WT1800. The selectable wiring systems vary depending on the
number of installed input elements.
• 1P2W: Single-phase, two-wire system
• 1P3W: Single-phase, three-wire system
• 3P3W: Three-phase, three-wire system
• 3P4W: Three-phase, four-wire system
• 3P3W(3V3A):
Three-voltage, three-current method
Wiring Unit
Wiring units are sets of two or three input elements of the same wiring system that are grouped together. You
can define up to three wiring units: ΣA, ΣB, and ΣC.
• When there is one wiring unit, that unit is ΣA. You cannot make ΣB or ΣC the first wiring unit.
• When there are two wiring units, those units are ΣA and ΣB. You cannot make ΣC one of the first two wiring
units.
• When there are three wiring units, those units are ΣA, ΣB, and ΣC.
• When there are multiple wiring units, element numbers are assigned to them in ascending order. The element
numbers are assigned to ΣA, ΣB, and then ΣC.
• Wiring units are composed of input elements that are next to each other. Wiring units cannot consist of input
elements that are not next to each other.
• A wiring unit must either be composed of only 50 A input elements or only 5 A input elements. Wiring units
cannot consist of different types of input elements.
Σ Functions
The measurement function of a wiring unit is called a Σ function.
For example, “UrmsΣA” corresponds to the average of the voltages of the input elements that are assigned to
the wiring unit ΣA. The average value represents the true rms value.
Wiring System Combinations
The following tables provide examples of the wiring system combinations that you can use and the input
elements that you can assign to wiring system ΣA, ΣB, or ΣC depending on the number of installed input
elements. In addition to the combinations indicated in the tables below, you can also configure any pattern that
meets the conditions for wiring units described above.
For details about the relationship between wiring systems and how the values of the measurement functions are
determined, see appendix 1 in the getting started guide, IM WT1801-03EN.