Current Measurement in Multi-Phase Networks Using Shifted Clock Patterns
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Solution Overview
Problem
Current multi-phase current measurement methods for electric motors with controllable bridges are inefficient, as they require high effort and cannot automatically track ripple offsets over the entire motor angular range, leading to inaccurate current measurements.
Innovation Solution
The method involves shifting clock patterns in order of increasing duty cycle, ensuring sufficient measuring windows for double scanning of phase currents using a single shunt, allowing for automatic ripple offset compensation across the entire motor angular range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple shunts are arranged in each phase line to record phase currents, then measurement capability is improved, but device complexity and cost increase
Solution Approach 1:
The patent merges multiple current measurement functions into a single shunt by sequentially measuring different phase currents through time-multiplexed switching. The single shunt serves multiple measurement purposes by combining spatial and temporal multiplexing, eliminating the need for separate shunts in each phase line.
Solution Approach 2:
The single shunt is designed to perform multiple functions by measuring currents from different phases at different time intervals. The measuring amplifier circuit and switching elements enable the shunt to universally measure any phase current by controlling the switching sequence, making one component serve multiple measurement roles.
2Measurement precision
If clock patterns are shifted to obtain measurement windows with sufficient temporal size, then measurement accuracy is improved, but measurement time increases
Solution Approach 1:
The patent employs periodic switching of clock patterns to sequentially measure different phase currents. By periodically switching between phases in a predetermined sequence, the system achieves sufficient measurement time for each phase while maintaining overall measurement efficiency through the periodic repetition of the measurement cycle.
Solution Approach 2:
The switching elements are pre-configured with predetermined switching sequences that prepare the measurement circuit for each phase in advance. The clock patterns are shifted beforehand to ensure that measurement windows are properly positioned and sized, allowing measurements to proceed without delays during the actual measurement phase.
3Reliability
If double sampling is carried out to detect a second current value, then measurement reliability is improved, but device complexity increases
Solution Approach 1:
The system achieves double sampling functionality through self-service by using the same single shunt and measuring amplifier circuit to perform multiple measurements. The switching elements automatically sequence the measurements, and the control unit handles the coordination, eliminating the need for additional dedicated sampling hardware while maintaining measurement reliability.
4Measurement precision
If ripple offsets are compensated with frozen values from memory, then compensation is achieved, but automatic tracking over entire motor angular range is not possible
Solution Approach 1:
The patent transitions from static frozen values to dynamic ripple offset compensation by continuously tracking offsets across the entire motor angular range. The system dynamically adjusts compensation values based on real-time measurements taken at different switching sequences and clock pattern positions, enabling adaptive compensation that follows motor operation throughout the full angular range.
Solution Approach 2:
The system implements feedback mechanisms where measurement results from double sampling are used to detect and compensate for ripple offsets. The control unit continuously monitors measurement accuracy and adjusts compensation parameters based on feedback from actual measurements, enabling automatic tracking and compensation across varying operating conditions and motor angles.
Data Source
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AI summary
The invention relates to a method for current measurement using a measuring amplifier circuit in a multi-phase power network, in which at least one controllable switching element of each phase supplies a desired current to an electrical load, and a control unit generates a control signal with a clock pattern controlling the on-time of the respective switching element in order to achieve the desired current. Clock patterns of the control signals are assigned measurement windows for current measurement, in particular for measuring phase currents, and clock patterns are shifted in time to obtain measurement windows of sufficient length. It is provided that the clock patterns of ascending on-time are shifted in order of priority, with the switching element with the shortest on-time being switched on first.