Secondary
current
Cross-section
Line resistances at different lead lengths (outgoing and return lead)
[A]
[mm²]
0.5 m
1.0 m
2.5 m
5 m
10 m
5
1.5
0.3 VA
0.6 VA
1.5 VA
2.9 VA
5.8 VA
5
2.5
0.2 VA
0.4 VA
0.9 VA
1.8 VA
3.6 VA
5
4.0 - -
0.6 VA
1.1 VA
2.2 VA
SELECTION CRITERIA FOR A CURRENT CONVERTER FOR
THE FRONIUS SMART METER 50KA-3
/ Primary current
Maximum current per phase. A current converter with a primary current greater than the maximum
expected current per phase should be selected. The closer the expected current is to this value, the
more precise the measurement will be.
/ Secondary current
1 - 5 A
/ Power
The Fronius Smart Meter needs 0.3 VA to carry out its measurements. Losses also occur on the
outgoing and return leads. The power of the current converter must be greater than the sum total of the
power of the Fronius Smart Meter and the leads. The higher the power, the better.
For example: Outgoing and return lead between Fronius Smart Meter and current converter (together):
2 x 0.5 m = 1 m length with a copper cable cross-section of 1.5 mm² -> 1 x 0.6 VA
Fronius Smart Meter self-consumption = 0.3 VA
Sum total = 0.9 VA
A current converter with a rating of 1 VA, 1.5 VA, 5 VA or higher is suitable here.
Line resistances at different cross-sections (copper wires)
/ Accuracy class
Class 1 or better (Class 0.5, 0.2, etc.) is recommended. Class 1 is equivalent to a deviation of ± 1% of
the secondary current at maximum power.
/ Assembly
Rigid or hinged. “Rigid” is usually cheaper with better power and accuracy values. “Hinged” can be
installed in a system without interrupting the voltage.
02/2011 1/1
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