1. DC measurements

1.1 Current measurement

A conventional current transformer performs three basic functions (see Measuring transformers. General information. Theory. Operation ) :

• isolation ;

• ampere-turn comparison ;

• energy transfer from primary to secondary.

As it becomes continuous, it can no longer perform the latter function. This is because the magnetic induction flux within the core is constant. It therefore generates no electromotive force in the secondary winding. The secondary current must be supplied by an auxiliary source, capable of providing the power dissipated by the load and the winding resistance.

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