Bridge Circuit Current Measurement for Commutated Motor Sector Transitions
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Solution Overview
Problem
Conventional current measurement systems in commutated motors, particularly during sector transitions in vector driving, are incomplete and unable to measure phase currents accurately, limiting motor regulation and noise reduction in applications like hybrid and electric vehicles.
Innovation Solution
A current measuring system with a bridge circuit featuring pulse-width modulators and current measuring circuits in both high-side and low-side branches, connected to an analog-digital converter, allowing precise acquisition and computation of phase currents for improved motor control and noise reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a simple shunt measuring system is used in bridge circuits, then the device complexity is reduced and manufacturing costs are lowered, but the measurement precision of phase currents during sector transitions becomes incomplete and insufficient for motor regulation
Solution Approach 1:
The measuring system is segmented by placing individual current measuring circuits in each branch of the bridge circuit rather than using a single shunt. This segmentation allows each branch current to be measured independently, providing complete phase current information during sector transitions while maintaining manageable system complexity through modular design
Solution Approach 2:
The current measuring circuits serve multiple functions: they measure branch currents during normal operation, provide accurate phase current data during sector transitions, enable field-oriented control, and support comprehensive motor regulation. This multi-functionality resolves the contradiction by making the measuring system indispensable despite increased complexity
2Object-affected harmful factors
If six-step commutation is used in commutated motors, then the ease of manufacture and implementation is improved, but the noise level increases and becomes noticeable in hybrid and electric vehicles
Solution Approach 1:
The measuring system provides real-time feedback on actual branch currents and phase currents during sector transitions. This feedback enables the control device to implement field-oriented control with precise current regulation, reducing torque ripples and noise while maintaining the simplicity of six-step commutation architecture
Solution Approach 2:
The system dynamically adjusts control parameters based on measured current values during sector transitions. By changing control parameters in real-time based on actual measurements, the system reduces noise and torque ripples while preserving the ease of six-step commutation implementation
3Loss of information
If a single-shunt measurement at the base point of the bridge circuit is used, then the device complexity is reduced, but the ability to acquire exact current and voltage values in the branches for field-oriented control is lost
Solution Approach 1:
Instead of a single shunt measurement, the system segments the measurement function by placing current measuring circuits in each bridge circuit branch. This segmentation captures exact current values in each branch and enables derivation of complete voltage and current information necessary for field-oriented control
Solution Approach 2:
The current measuring circuits act as intermediaries between the bridge circuit branches and the control device. They provide the control device with accurate current information from each branch, enabling precise field-oriented control without requiring direct complex measurement arrangements
Data Source
AI summary
A current measuring system (10) for a commutated motor (20). The current measuring system comprises a bridge circuit (30) with several branches (30a-c), wherein the branches (30a-c) are in each case connected to commutation blocks of the commutated motor (20), and the branches (30a-c) each have a current measuring circuit (60a-c).