Motor Drive Cable Resistance Sensing for Precise Converter Control
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Solution Overview
Problem
Conventional drive systems face challenges in accurately determining cable resistance, which affects the control quality of electric motors.
Innovation Solution
A drive system that includes an electric motor, a converter, and a hybrid cable with specific electrical line configurations. The system employs a voltage detection device to measure voltage drops between electrical lines and a current detection device to measure currents, allowing for the determination of cable resistance and its incorporation into stator flux-oriented control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If cable resistance is not accurately determined, then control quality deteriorates, but implementing voltage and current detection devices increases device complexity
Solution Approach 1:
The patent reuses existing electrical lines (second electrical line for voltage detection, third electrical lines for current detection) that are already part of the cable system, making these lines serve multiple functions: power transmission and measurement simultaneously. This avoids adding separate dedicated measurement lines and reduces overall system complexity.
Solution Approach 2:
The system uses the cable's own electrical lines to perform self-diagnosis and measurement of cable resistance. The second electrical line and third electrical lines that carry power also carry measurement signals, allowing the system to monitor its own state without external intervention or additional complex measurement infrastructure.
2Measurement precision
If separate measurement lines are added for voltage detection, then measurement precision improves, but cable complexity and installation space requirements increase
Solution Approach 1:
The patent makes the existing second electrical line serve dual purposes: it carries power to the motor and simultaneously serves as a measurement line for detecting voltage drops. This eliminates the need for separate dedicated voltage measurement lines, maintaining measurement precision while avoiding increased cable complexity.
Solution Approach 2:
The patent merges the power transmission function and measurement function into the same electrical lines. The second electrical line is used both for supplying power and for voltage detection, while the third electrical lines serve both as current carriers and current measurement conduits, consolidating functions rather than separating them.
3Measurement precision
If the measuring line carries motor current, then accurate cable resistance determination is achieved, but the measuring line requires high current capacity increasing cable space requirements
Solution Approach 1:
The patent makes the third electrical lines serve dual purposes: they carry the high motor current to the motor and simultaneously serve as the path for current detection. By reusing these high-current-capable lines for measurement purposes, the system achieves accurate current measurement without requiring separate low-current measurement lines, thus avoiding increased cable cross-section.
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
Regularly updating cable resistance improves control quality by ensuring accurate parameters during the control process, enhancing the efficiency and precision of motor control.
Implementation Method 1
A voltage detection device arranged on the first cable end detects a voltage present between the second electrical line and a further electrical line
Implementation Method 2
The current flowing through the further electrical line is detected by a current detection device
Implementation Method 3
a resistance value is determined from the detected voltage and the detected current
Implementation Method 4
the measuring line is connected in a heat conducting manner to the line carrying the motor current such that the temperature of the measuring line is equal to the temperature of the line carrying the motor current
Data Source
AI summary
A drive system includes an electric motor and a converter that feeds the electric motor. A cable electrically connects the electric motor to the converter and has first electrical lines, a second electrical line, and third electrical lines. A voltage detection device arranged on the first cable end detects a voltage present between the second electrical line and a further electrical line, e.g., a measuring line. The further electrical line is one of the first electrical lines or one of the third electrical lines, and the further electrical line is electrically connected to the second electrical line on the second cable end. The current flowing through the further electrical line is detected by a current detection device, and a resistance value is determined from the detected voltage and the detected current and is provided to a control unit of the converter.