Specification
13
3.5 GENERATOR CURRENT SENSING
Measurement type True RMS conversion
Sample Rate 5 kHz or better
Harmonics Up to 10
or better
Nominal CT secondary rating 1 A or 5 A (5 A recommended)
Maximum continuous current 5 A
Overload Measurement 3 x Nominal Range setting
Absolute maximum overload 50 A for 1 second
Burden
0.5 VA (0.02 Ω current shunts)
common mode offset ±2 V peak plant ground to CT common terminal
Resolution 0.5 % of 5 A
Accuracy ±1 % of Nominal (1 A or 5 A) (excluding CT error)
3.5.1 VA RATING OF THE CTS
The VA burden of the module on the
CTs is 0.5 VA. However depending
upon the type and length of cabling
between the CTs and the module, CTs
with a greater VA rating than the
module are required.
The distance between the CTs and the
measuring module should be
estimated and cross-referenced
against the chart opposite to find the
VA burden of the cable itself.
If the CTs are fitted within the
alternator top box, the star point
(common) of the CTs should be
connected to system ground (earth) as
close as possible to the CTs. This
minimises the length of cable used to
connect the CTs to the DSE module.
Example.
If 1.5 mm² cable is used and the
distance from the CT to the measuring
module is 20 m, then the burden of the
cable alone is approximately 15 VA.
As the burden of the DSE controller is
0.5 VA, then a CT with a rating of at
least 15+0.5 V = 15.5 VA must be
used.
If 2.5 mm² cables are used over the
same distance of 20 m, then the
burden of the cable on the CT is
approximately 7 VA. CT’s required in
this instance is at least 7.5 VA (7+0.5).
NOTE: - Details for 4 mm² cables are shown for reference only. The connectors on the
DSE modules are only suitable for cables up to 2.5 mm².
NOTE: - CTs with 5 A secondary windings are recommended with DSE modules. 1 A CTs
can be used if necessary however, the resolution of the readings is 5 times better when using
5 A CTs.
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