Current transformer

In principle, the choice of current transformer for the EL3773 is not critical. The internal resistance within the current circuit of the EL3773 is so small that it is negligible for the calculation of the total resistances of the current loop. The transformer must be able to supply a secondary rated current of 1 or 1.5 A; the primary rated current I_pn can be chosen as desired. Overloading of the EL3773 is permissible up to 1.2 x I_pn/U_pn; see Technical Data for max. permissible overvoltage/overcurrent.

Accuracy

Please note that the overall accuracy of the set-up consisting of EL3773 and current transformers to a large degree depends on the accuracy class of the transformers.

	No approval as a billing meter A set-up with a class 0.5 current transformer cannot be approved or authenticated. The EL3773 is not an approved billing meter according to the electricity meter standard (DIN 43 856).

Current types

The EL3773 can measure any type of current.

Overcurrent limiting factor FS

The overcurrent limiting factor FS of a current transformer indicates at what multiple of the primary rated current the current transformer changes to saturation mode, in order to protect the connected measuring devices.

Note

Attention! Risk of damage to the device!

The max. permissible input values according to the Technical Data must be observed!
Additional intermediate transformers must be used in systems in which the overcurrent limiting factors of the transformer allow higher secondary currents!

Protection against dangerous touch voltages

During appropriate operation of the EL3773 with associated current transformers, no dangerous voltages occur. The secondary voltage is in the range of a few Volts. However, the following faults may lead to excessive voltages:

Open current path of one or more transformers
Neutral conductor cut on the voltage measurement side of the EL3773
General insulation fault

WARNING

WARNING Risk of electric shock!

The complete wiring of the EL3773 must be protected against accidental contact and equipped with associated warnings! The insulation should be designed for the maximum conductor voltage of the system to be measured!

The EL3773 allows a maximum voltage of 500 V for normal operating conditions. The conductor voltage on the current side must not exceed 500 V! For higher voltages, an intermediate transformer stage should be used!

On the voltage measurement side, a EL3773 is equipped with a protection impedance of 1.8 MΩ. If the neutral conductor is not connected and only one connection on the side of the voltage measurement is live, the resulting voltage against earth in a 3-phase system with a phase-to-phase voltage of 400 V_AC is 230 V_AC. This should also be measured on the side of the current measurement using a multimeter with an internal resistance of 10 MΩ, which does not represent an insulation fault.

Additional measuring instruments in the current circuit

Please note that the addition of additional measuring instruments (e.g. ammeters) in the current circuit can lead to a significant increase in the total apparent power.

Furthermore, connection I_N of the EL3773 must represent a star point for the three secondary windings. Additional measuring instruments therefore have to be potential-free and must be wired accordingly.