Galvanic Insulation Voltage Measurement Using Transformer Tap
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Solution Overview
Problem
Existing devices for measuring alternating voltage in electric mains lines face challenges due to the high cost and bulkiness of measuring transformers, and the unreliability of measurements using pre-existing supply transformers, which are affected by non-linear absorption and environmental factors.
Innovation Solution
A device that uses a supply transformer with its primary winding connected to the mains and secondary winding connected to both the supply and measuring circuits, employing full-wave rectification and a microcontroller to sample the voltage during non-conducting intervals of the supply circuit, thereby isolating the measurement from load effects and using sinusoidal interpolation for accurate voltage measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a measuring transformer is used to convert alternating mains voltage, then galvanic insulation and measurement reliability are improved, but device cost and size increase
Solution Approach 1:
The patent applies multi-functionality by using the supply transformer's secondary winding for both power supply and voltage measurement functions. The measuring circuit taps the secondary winding voltage to obtain measurement information while the same winding simultaneously powers the measuring instrument, eliminating the need for a separate dedicated measuring transformer.
Solution Approach 2:
The patent extracts the measurement function from the supply circuit by implementing a separate measuring circuit that independently processes a portion of the secondary winding voltage. This extraction allows the measurement system to operate independently from the power supply load variations, achieving reliable measurements without requiring a bulky dedicated measuring transformer.
2Weight of stationary object
If a pre-existing supply transformer is used for measurement, then device cost and size are reduced, but measurement precision deteriorates due to non-linear absorption and environmental factors
Solution Approach 1:
The patent segments the secondary winding voltage into two distinct functional paths: one for power supply and one for measurement. The measuring circuit receives a tapped portion of the secondary voltage that is processed separately from the main power supply circuit, isolating measurement signals from load-induced distortions and environmental variations.
Solution Approach 2:
The patent introduces an intermediary measuring circuit that acts as a buffer between the supply transformer and the measurement processing. This intermediary circuit converts the secondary winding voltage into a stable measurement signal through rectification and filtering, isolating the final measurement from the non-linear effects of the power supply load.
3Device complexity
If the secondary winding is used for both supply and measurement, then device complexity is reduced, but measurement reliability deteriorates due to load effects on the transformer
Solution Approach 1:
The patent applies preliminary action by performing rectification and filtering of the secondary winding voltage before it reaches the measurement circuit. The measuring circuit processes a pre-processed version of the voltage signal that has already been conditioned to remove load-induced variations, ensuring reliable measurements are obtained in advance of any measurement operations.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides a compact, economical, and highly accurate measurement of alternating voltage, independent of load absorption and environmental factors, with reduced hysteresis effects, achieving precision comparable to dedicated measuring transformers.
Implementation Method 1
the transformer, with a supply function, having its primary winding connected to the electric mains on which the measurement has to be carried out
Implementation Method 2
a first element, configured to convert the alternating voltage of the secondary winding into a direct voltage
Data Source
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AI summary
Measuring device, of the galvanic insulation type, to measure an alternating voltage (U1) of an electric mains line, comprising a measuring circuit (35), having a microcontroller, a supply circuit (33) able to supply the measuring circuit (35), and a transformer (T), having a primary winding powered by the mains sinusoidal voltage (U1), connected to said electric line, and a secondary winding with a voltage (U2), connected both to said measuring circuit (35) and also to said supply circuit (33). The supply circuit (33) and the measuring circuit (35) comprise respectively a first and a second full-wave rectifier elements (BRG, BRG'), distinct from each other, wherein the second rectifier element (BRG') is configured so as not to generate load effects on the secondary winding of the transformer (T), and the rectifier element (BRG') is loaded with a high value impedance (R').