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FAQ for Measuring Transducers
- Why do primary values for current and voltage transformers as well as the upper power range value have to be specified when ordering
power measuring transducers?
- What significance does the calibration factor have in laying out a measuring transducer?
- How is cos phi measured?
- What are the differences between power factor I and power factor II?
- How is 4 quadrant power factor measurement performed?
- Which factors need to be observed in laying out a cos phi measuring transducer?
- What is the significance of the terms angle proportional
(or angle linear) and cos phi proportional (or cos phi linear) in relation to cos phi transducers?
- Measurements in distorted electrical systems?
- Are your measuring transducers also suitable for 690 V electrical systems?
- How is input voltage (nominal voltage) defined for
power measuring transducers in 3-phase electrical systems?
- How can power measuring transducers be recalibrated?
- The DME4 changes its output signal when the ripple control frequency is applied. Why?
- What is meant by calibration of the secondary side?
Correct measurement – in distorted electrical systems as well!
There are two types of current and voltage measuring transducers:
1. one for measuring the arithmetic mean value (calibration for sinusoidal quantities, form factor = 1.11) and
2.
one for RMS measurement with distorted waveshapes (AC coupling).
RMS power measurement is correct up to approximately the 16th harmonic. In the case of commercially available cos phi transducers which only evaluate the difference in zero-crossings, it must be assured that no additional zero-crossings result from the harmonics. Transducers which generate Pactive / Papparent quotients are better suited in this case, for example multi-transducers (DME4.., M563). As a rule, frequency measuring transducers are equipped with input filters which only evaluate the fundamental frequency.
Are your measuring transducers also suitable for 690 V electrical systems?
530 series instruments and DME4... multi-transducers are best suited for the performance of measurements in 690 V
systems.
How is input voltage (nominal voltage) defined for power measuring transducers in 3-phase electrical systems?
Input voltage (nominal voltage) is generally defined as line-to-line voltage in 3-phase systems. 530 series instruments and DME4... multi-transducers are best suited for the performance of measurements in 690 V systems.
How can power measuring transducers be recalibrated?
The older analog devices must be recalibrated at the factory.
Series 530 devices can be recalibrated on-site with only minimal measuring effort within the range specified by the calibration factor (see operating instructions). Multi-transducers (DME4..., M563) can be recalibrated on-site with the help of the software required to this end.
Ripple control frequencies (signals) are superimposed as phase voltage signals, and thus change the RMS value of the phase voltage. Measuring transducers with correct RMS measurement evaluate this rise in voltage as a measuring signal, and change the output signal by the amount of influence resulting from the ripple control frequency. Special layouts with corresponding filters remedy this situation is some cases.
