To reduce the no-load current in the core, a good quality material may be used in its construction, which will also decrease the magnetization power and the loss power while maintaining the magnetic flux. However, this method has a reasonable limit.
Applying special materials such as permalloy, for example, the vacuum current could be greatly reduced, but the high cost would not compensate the gain, because the voltage drops caused by the vacuum current are only a group of contributors to the errors of a TP.
As a rule, good grade silicon iron is used in TP-s of industrial applications (class 0.3 – 0.6 – 1.2), and for TP-s for laboratory (or standards) applications, it employs more noble materials, such as silicon with magnetic orientation.
To reduce the errors of a TP, the most efficient method is the reduction of internal impedances, which can be reduced by a correct sizing. Therefore, a TP is nothing more than an oversized power transformer. overload clutch orc3spclp29
To characterize this, we talk about the “limiting power” of a TP, which is the power at which a TP can stand and function as a power transformer. The limiting power (Pl) is n times greater than the nominal power (Pn) of a TP.