Description:
Summation current transformers for primary rated currents with 5 A or 1 A, secondary rated current 5 A, 2 A or 1 A, in accuracy classes 0.2, 0.5 and 1. The number following the type designation provides information on the number of main transformers to be connected – up to 8 primary inputs can be realised.
Summation current transformers enable the summation of several synchronous alternating currents with the same phase position but different load phase shifts. It is also possible to totalise currents with different nominal voltages in the same phase position. However, these measurements cannot be used for calculation purposes, as the existing voltage differences are fully included in the measurement as errors.
By connecting the main transformers to the summation current transformer in opposite directions, it is possible to obtain secondary currents that are proportional to the difference between the primary input currents.
Design measures in the manufacture of the summation current transformer make it possible to add secondary currents from main transformers with different nominal transformation ratios.
The secondary connections of each main transformer are connected to the primary input of the summation current transformer assigned to it.
For main transformers with different nominal transformation ratios, ensure that they are connected correctly to the input of the summation current transformer assigned to them. If no current flows in the main transformer, the secondary circuit of this main transformer must not be short-circuited either at the summation current transformer or at the main transformer.
If a summation current transformer has an unused primary circuit for the subsequent connection of another main transformer, this circuit must remain open. In this case, the secondary output current of the summation current transformer is lower than the secondary rated current of the summation current transformer by the ratio of the primary rated current of this “missing” main transformer to the sum of all primary rated currents of the main transformers.
The secondary rated current of a main transformer must be equal to the primary rated current of the input of the summation current transformer assigned to it.
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