Power Steering Motor Fault Braking Before Phase Disconnection
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Solution Overview
Problem
In electromechanical motor vehicle power steering systems, electrical short-circuit faults lead to unintended braking torque due to closed conductor loops, causing safety issues and potential damage to phase disconnection devices, which existing solutions address inadequately with bulky and costly components.
Innovation Solution
A method involving a control unit that monitors switching elements for faults, initiates a controlled braking period by switching on additional switching elements to reduce rotor speed before disconnecting phase windings, thereby reducing induction voltages and allowing safer, quicker disconnection of the electric motor from the DC voltage source.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If phase disconnection devices are suddenly disconnected during rapid motor rotation, then current interruption capability is improved, but high induction voltages arise that can exceed breakdown voltages and damage the phase disconnection devices
Solution Approach 1:
The control unit determines a safe disconnection time point before actually disconnecting the phase windings. This preliminary determination allows the system to wait for favorable conditions (low induction voltage) before executing the disconnection, preventing damage to phase disconnection devices while maintaining current interruption capability
Solution Approach 2:
The control unit continuously monitors motor rotation speed and dynamically determines the disconnection time point based on real-time conditions. This feedback mechanism ensures that disconnection only occurs when induction voltages are sufficiently low, adapting to varying operational states to prevent device damage
2Reliability
If oversized phase disconnection devices are used to prevent damage from induction voltages, then device reliability is improved, but device size and cost increase
Solution Approach 1:
By determining a safe disconnection time point in advance based on motor rotation speed, the system ensures that disconnection occurs under favorable conditions. This allows the use of smaller, less expensive phase disconnection devices that are adequately protected by the timing control rather than requiring oversized protective components
Solution Approach 2:
The system changes the operational parameters of phase disconnection devices by controlling the timing of disconnection based on motor rotation speed. This parameter-based control approach replaces the need for oversized hardware protection with intelligent timing, reducing device size and cost while maintaining reliability
3Reliability
If phase disconnection devices are used to interrupt current in short-circuit faults, then fault protection is improved, but device complexity and cost increase
Solution Approach 1:
The control unit performs multiple functions: it controls normal motor operation, monitors for short-circuit faults, determines safe disconnection time points, and executes disconnection. This multi-functionality eliminates the need for separate complex protection circuits, reducing overall device complexity while maintaining fault protection capability
Solution Approach 2:
The control unit uses its existing monitoring and control capabilities to also perform fault detection and protection functions. By making the control unit self-sufficient for multiple tasks including fault protection, the system avoids adding separate protection devices, thereby reducing complexity and cost
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 enables safe and rapid disconnection of the electric motor, preventing overvoltages and allowing for smaller, less expensive phase disconnection devices by actively managing braking torque and reducing residual energy, thus enhancing system safety and efficiency.
Implementation Method 1
the rotation of the rotor induces a current in the conductor loop, which current in turn generates a magnetic field
Implementation Method 2
the rotation of the rotor induces a current in the conductor loop, which current in turn generates a magnetic field that counteracts the rotation of the rotor
Data Source
AI summary
A multiphase electric motor is disconnectable from a DC voltage source by way of a control unit. Phase windings with connection lines can each be alternately connected via a high-side and a low-side switching element to a respective pole of the DC voltage source, and the connection lines each have a device for disconnecting the phase windings from the DC voltage source upon a fault. The control unit may monitor the switching elements for short-circuit faults, switch off the switching elements when a fault occurs, determine whether the switching element causing the fault is a high-side or a low-side switching element, switch on at least a second of the high-side or correspondingly at least a second of the low-side switching elements in addition to the switching element causing the fault to brake the electric motor, switch off the switching elements after a braking period, and open the phase disconnection devices.