Electric Machine Control for Braking Torque Without Battery Charging
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Solution Overview
Problem
Electric vehicles face challenges in generating additional torque during downhill driving or when the battery is fully charged, defective, or disconnected, as conventional electric motors cannot produce torque without supplying energy to the battery or consumer, leading to oversized brake systems.
Innovation Solution
A control system for electric machines that allows for the generation of braking torque by limiting electrical power to a minimum value or zero, using a control facility to manage generator voltage and current through an electronic power system, including a switch unit for short-circuiting and determining rotational speed to calculate optimal generator currents and phase angles, thereby relieving mechanical brakes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the electric motor generates torque by supplying current to the battery or consumer, then the motor can produce the required braking torque, but the electrical power increases beyond acceptable limits when the battery is fully charged, defective, or disconnected
Solution Approach 1:
The patent converts the harmful situation of the battery being unable to accept energy (fully charged, defective, or disconnected) into a beneficial braking mode. By detecting this condition and switching to a control mode that limits electrical power while maintaining braking torque generation, the system transforms a problematic state into a useful operational mode for relieving mechanical brakes.
Solution Approach 2:
The control facility changes the operational parameters of the electric machine by limiting the electrical power to a predetermined minimum value when the battery cannot accept energy. This parameter change allows the system to generate braking torque through alternative control strategies that do not rely on high electrical power output to the battery.
2Force
If the conventional brake system is dimensioned to provide additional torque for downhill driving or trailer towing, then the required braking force can be achieved, but the brake system becomes oversized and less efficient
Solution Approach 1:
The patent merges the functions of the electric machine and the mechanical brake system into a coordinated hybrid braking system. The electric machine provides regenerative braking torque that supplements the mechanical brakes, allowing the mechanical brake system to be downsized while maintaining overall braking performance. This combination enables the system to achieve required braking force without oversizing the mechanical components.
Solution Approach 2:
The electric machine serves multiple functions: it acts as a motor during acceleration, a generator for regenerative braking when the battery can accept energy, and a controlled braking device when the battery cannot accept energy. This multi-functionality allows the mechanical brake system to be optimized for its primary function without needing to be oversized for all braking scenarios.
3Force
If the electric motor operates without limiting electrical power, then maximum braking torque can be generated, but the system cannot maintain control when the battery is fully charged, defective, or disconnected
Solution Approach 1:
The control facility continuously monitors the battery's energy acceptance capability and adjusts the electric machine's operation accordingly. When the battery is fully charged, defective, or disconnected, the control system detects this condition and implements power limiting while maintaining braking torque generation. This feedback mechanism ensures reliable control across all operational conditions.
Solution Approach 2:
The system dynamically adapts its control strategy based on real-time conditions. The control facility switches between different operational modes: unrestricted power mode when the battery can accept energy, and power-limited mode when it cannot. This dynamic adaptation maintains braking torque generation capability while ensuring reliable control under varying battery conditions.
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
Enables controlled braking torque generation without charging the battery, reducing the load on mechanical brakes and maintaining electrical power within predetermined limits, suitable for electric and hybrid vehicles.
Implementation Method 1
the electric motor generates a recuperation energy that is generated from the kinetic movement energy of the vehicle
Implementation Method 2
the control facility comprises a switch unit which is connected to machine clamps and/or to the electronic power system and which is configured so as to switch a short circuit at the machine clamps and/or at the electronic power system
Data Source
AI summary
The present invention relates to a control system (10) for an electric machine (EM), for producing a braking torque, by means of the electric machine (EM), in a traction drive, said system comprising a control device (SE), the control device (SE) being configured to control a generator voltage or a generator current in or through a power electronics system (LE) of the electric machine such that during a movement of the traction drive, the electric power (Pel) of the electric machine (EM) can be limited to a level at least below a predefined minimum value.