Force Measuring Device With Dual Windings For Constant Power

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Solution Overview

Problem

Force-measuring devices based on electromagnetic force compensation face challenges with power fluctuations and noise generation due to changing heat release, leading to instability in measurement accuracy and efficiency, particularly when measuring different forces or loads.

Innovation Solution

A force-measuring device with two windings and partial current sources, where currents are controlled to maintain constant power output, reducing noise and optimizing temperature distribution, allowing for independent management of force and power generation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Force

If the compensation current is increased to generate higher compensation force, then the measurement range is extended, but the power consumption increases and heat release changes causing zero point instability

Engineering Contradiction:
Improvecompensation forceVSAvoidzero point stability
Core Design Contradiction:
ForceVSReliability

Solution Approach 1:

The patent applies periodic action by superimposing an alternating current component on the compensation current. This AC component causes the coil to generate periodic electromagnetic forces that alternate in direction, but the time-averaged effect produces additional power consumption (I²R losses) without significantly affecting the average compensation force. This periodic modulation allows the system to consume more power and generate more heat in a controlled manner, stabilizing the zero point while maintaining the required compensation force capability.

Inventive Principle:
Principle #19Periodic action

Solution Approach 2:

The patent changes the electrical parameters of the coil by superimposing an AC current component on the DC compensation current. This parameter change transforms the power consumption characteristic from being solely dependent on the compensation force magnitude to being enhanced by the AC component's contribution to I²R losses. The system dynamically adjusts the AC component's amplitude to control the total power consumption and heat generation, thereby stabilizing the zero point while maintaining measurement capability.

Inventive Principle:
Principle #35Parameter changes

2Reliability

If additional power consumers are used to maintain constant power, then zero point stability is improved, but device complexity increases

Engineering Contradiction:
Improvezero point stabilityVSAvoidcircuit complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent merges the power consumption function with the existing compensation coil structure. Instead of adding separate power consumers (heaters, resistors, etc.), the system uses the same coil that generates compensation force to also generate controlled heat through superimposed AC current. This merging eliminates the need for additional power consumer components and their associated control circuits, maintaining zero point stability while avoiding increased device complexity.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The patent makes the compensation coil multi-functional: it simultaneously performs its primary function of generating compensation force and its secondary function of generating controlled heat for zero point stabilization. By superimposing AC current on the DC compensation current, the single coil structure achieves both measurement and thermal stabilization functions, eliminating the need for separate dedicated power consumers and reducing overall system complexity.

Inventive Principle:
Principle #6Universality (Multi-functionality)

3Reliability

If bifilar coil configuration is used for power consumption, then constant power is achieved, but efficiency is reduced due to anti-parallel arrangement

Engineering Contradiction:
Improvepower constancyVSAvoidefficiency
Core Design Contradiction:
ReliabilityVSLoss of energy

Solution Approach 1:

The patent inverts the conventional approach to achieving constant power. Instead of using anti-parallel bifilar windings that cancel each other's electromagnetic effects (as in DE 28 19 451), the patent uses a single winding with superimposed AC current. This inversion allows the electromagnetic force generation and heat generation functions to be decoupled: the DC component provides compensation force while the AC component provides controlled heat, both in the same winding, thereby improving efficiency while maintaining power constancy.

Inventive Principle:
Principle #13The other way round (Inversion)

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

This approach enhances measurement accuracy and stability by maintaining constant power output, reducing noise, and optimizing the use of available space, thereby improving the overall efficiency and range of the force-measuring device.

Implementation Method 1

an electrical coil (53) which is movably arranged in a magnet system (50) and has at least two windings (W1, W2)... a current is passed through the windings (W1, W2) in each case as a function of the force acting on the force-measuring device in such a way that the at least two generated electromagnetic forces in their sum form the compensation force

Methodology Applied
Scientific EffectElectromagnetic force: Lorentz Force

Implementation Method 2

the power generated by the compensation current in the coil depends on the compensation current that is currently flowing and thus on the acting force... different power levels are also generated and released in the form of heat

Methodology Applied
Scientific EffectJoule heating: Joule Heating

Data Source

PatentEP2253944B1Controlled and/or regulated force measuring device
Publication Date: 2017.01.25 METTLER TOLEDO GMBH
  • EP2253944B1 patent drawingFigure 1~2
  • EP2253944B1 patent drawingFigure 3
  • EP2253944B1 patent drawingFigure 4a~4d

AI summary

The device has an electrical coil (53) movably arranged in a magnetic system (50) and including two windings (W1, W2). A powering device (PB) has partial current sources (PB1, PB2) that are associated to the windings. A control and/or regulating device (CU) controls and/or regulates powering of the windings by the sources such that current is conveyed through the windings depending on a load acting on the measuring device to form a compensation load by sum of two produced electromagnetic loads and the power that is delivered by the coils simultaneously sets a predetermined constant value.