Inductive voltage division is one of the fundamental techniques of electrical measurement technology. The use of these precise measuring transducers enables the accurate recording of electrical quantities in a wide range of applications. In particular, the combination of accuracy and robustness makes this technology indispensable for modern measurement tasks.
What are inductive voltage dividers?
Inductive voltage dividers work according to the transformer principle and use the magnetic coupling between primary and secondary windings for precise voltage division. The main difference to conventional transformers lies in the special winding arrangement, which ensures a particularly high measurement accuracy. The primary winding picks up the voltage to be measured, while the secondary winding supplies a proportionally reduced image of this voltage. The galvanic isolation between input and output provides an additional important safety aspect for high-voltage measurements. The accuracy of the measurement is largely determined by the quality of the core material and the precision of the windings.
Physical principles of inductive voltage division
Faraday’s law of induction and its significance for voltage dividers
The physical basis for the functioning of inductive voltage dividers is Faraday’s law of induction. The change in magnetic flux over time induces a voltage in the secondary winding, the magnitude of which depends on the ratio of the number of turns. Precise coordination of the magnetic coupling plays a decisive role in the design. Stray fields and parasitic capacities must be minimised by suitable shielding measures. The exact calculation of the induced voltage is carried out taking into account the winding geometry and the magnetic properties of the core material.
Magnetic coupling and transformer principle
The magnetic coupling between the windings is a major factor in determining the precision of the transducer. A high permeability core concentrates the magnetic flux and ensures almost loss-free transmission. The transformation ratio is determined by the ratio of the number of turns and remains constant over a wide frequency range. Optimisation of the winding configuration reduces leakage inductance and improves the linearity of the transmission. Modern core materials enable measurement accuracies in the range of a few ppm.
Designs and design principles
The design principle of inductive voltage dividers is based on a precise arrangement of the windings around a magnetic core. The mechanical stability of the construction plays a central role in the long-term stability of the measurement results. In particular, the symmetrical arrangement of the windings minimises parasitic effects. Various designs enable optimisation for specific applications, with toroidal cores often being used for precision measurements. The thermal design takes power losses into account and ensures stable measurement conditions even during longer series of measurements.
Core materials and their properties
The selection of the core material has a decisive influence on the performance of the transformer. Nanocrystalline materials offer an excellent combination of high permeability and low losses. Magnetic saturation must be taken into account in the dimensioning to avoid non-linearities. Ferrites are particularly suitable for high-frequency applications, while metal tape cores offer advantages for low-frequency measurements. The temperature stability of the magnetic properties ensures reliable measurements over a wide temperature range.
Winding types and their influence on measurement accuracy
The winding technology largely determines the achievable measurement accuracy. Multilayer windings require special care with the insulation between the layers. Capacitive coupling between the windings must be minimised by suitable winding methods. Tape-wound technology enables particularly homogeneous winding distributions and reduces stray capacitance. The use of shielding windings prevents the coupling of external interference fields and improves measurement stability under unfavourable ambient conditions.
Applications in measurement technology
High-voltage measurement technology
In high-voltage measurement technology, inductive voltage dividers enable precise measurements with minimal load on the test object. The galvanic isolation ensures maximum safety for operating personnel and measuring instruments. The dielectric strength of the insulation between the windings is particularly important. The dimensioning takes partial discharges into account and prevents local field intensifications. Modern designs achieve measurement accuracies in the range of 0.1% at voltages of up to several hundred kilovolts.
Precision measurements in the laboratory
Laboratory applications place the highest demands on the measurement accuracy of inductive voltage dividers. The calibration of measuring instruments requires reference accuracies in the ppm range. Temperature-stabilised measuring setups minimise the influence of ambient conditions. Shielding against electromagnetic interference plays a central role in precision measurements. Modern laboratory measuring transducers have integrated temperature monitoring and automatic correction options for systematic error influences.
Advantages and limitations of inductive voltage dividers
The strengths of inductive voltage dividers lie in their high precision and long-term stability. The wide frequency range enables a wide range of applications in measurement technology. In particular, the galvanic isolation between input and output offers safety advantages. The limits are determined by parasitic effects at very high frequencies. The mechanical construction influences the robustness against shocks and temperature fluctuations. Modern developments are aimed at extending the usable frequency range and improving measurement stability.
Measurement accuracy and interference sensitivity
The attainable measurement accuracy depends on various factors. Magnetic leakage fields influence the transmission accuracy and must be minimised by suitable shielding measures. Capacitive coupling between the windings limits the bandwidth at high frequencies. Temperature effects lead to slight changes in the magnetic properties of the core material. Optimisation of the winding geometry reduces the influence of parasitic capacities and improves the linearity of the transmission.
Frequency response and bandwidth
The frequency response of inductive voltage dividers is determined by various physical effects. Eddy current losses in the core material increase with rising frequency. The self-resonance of the windings limits the usable frequency range upwards. Capacitive effects between the windings influence the transmission behaviour at high frequencies. Careful tuning of the design parameters enables optimal measurement results in the specified frequency range.
Calibration and maintenance
Regular calibration of inductive voltage dividers ensures their long-term measurement accuracy. Precise reference standards serve as the basis for the traceability of measured values. Calibration documentation allows changes to be tracked over time. Maintenance intervals depend on the operating conditions and accuracy requirements. Professional cleaning and checking of the insulation properties are included in the standard maintenance.
Calibration procedure and intervals
The choice of the calibration procedure depends on the required measurement accuracy. Comparative measurements with higher-quality standards form the basis of the calibration. The measurement uncertainty must be determined for the entire transmission range. Temperature and humidity during calibration are documented. Traceability to national standards ensures comparability of measurement results. Digital calibration protocols facilitate the management of calibration data.
Sources of error and how to avoid them
Systematic sources of error must be taken into account during measurement. Temperature-dependent changes in magnetic properties affect measurement accuracy. Additional shielding measures can be used to reduce electromagnetic interference. Regular checking of the insulation resistance prevents creeping deterioration. Mechanical vibrations can influence the winding geometry and should be minimised. Documentation of errors that occur helps to optimise the measurement conditions.
New fields of application
The development of new measurement tasks opens up additional fields of application for inductive voltage dividers. The field of power quality measurement requires precise voltage detection over wide frequency ranges. Modern energy systems with a high proportion of renewable sources place new demands on measurement technology. Integration into smart grid applications requires advanced communication capabilities. Future developments will aim to combine several measurement functions in a single device. Miniaturisation enables use in mobile measuring devices.