Current transformer
In principle, the choice of current transformer for the EL34x3 is not critical. The internal resistance within the current circuit of the EL34x3 is so small that it is negligible for the calculation of the total resistances of the current loop. The transformers must be able to supply a secondary rated current in accordance with the set measuring range. The primary rated current Ipn can be selected arbitrarily. The common permissible overload of 1.2 x Ipn is no problem for the EL34x3, but may lead to small measuring inaccuracies.
Accuracy
Please note that the overall accuracy of the set-up consisting of EL34x3 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 EL34x3 is not an approved billing meter according to the electricity meter standard (DIN 43 856). |
Current types
The EL34x3 terminals can measure AC currents with a frequency of 45 Hz to 65 Hz and up to their 21st harmonic. Since such currents are frequently created by inverters and may contain frequencies of less than 50 Hz or even a DC component, electronic transformers should be used for such applications.
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 instruments.
Notice | |
Attention! Risk of damage to the device! The EL34x3 terminals may not be continuously loaded with more than 5 A [EL3413-xxxx] or 10 A [EL3433-xxxx] respectively! 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 EL34x3 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 circuit of one or several transformers
- Neutral conductor cut on the voltage measurement side of the EL34x3
- General insulation fault
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WARNING Risk of electric shock! The complete wiring of the EL34x3 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 EL3413-xxxxx or EL3433-xxxx allows the maximum voltage for normal conditions as specified in the technical data. The conductor voltage on the current side must not exceed this value! For higher voltages, an intermediate transformer stage should be used!
An EL34x3 is equipped with a protective impedance of typically 1 MΩ on the voltage measurement side. If the neutral conductor is not connected and only one connection is live on the voltage measurement side, the resulting voltage against earth in a 3-phase system with a specific line-to-line voltage is reduced by the factor √3. 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.