Switched Reluctance Motor Current Profile Strategy for Torque Ripple
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Solution Overview
Problem
Existing control schemes for switched reluctance machines fail to effectively manage torque ripple and phase current, leading to inefficiencies and excessive heat generation due to high transient currents, which are not cost-effectively addressed by current systems.
Innovation Solution
A method and system where a controller determines a desired torque and calculates currents for each phase of the electric motor, limiting currents to a threshold when exceeding rated levels and adjusting adjacent phases to compensate for torque shortfalls, thereby minimizing torque ripple and phase current while avoiding overcurrent conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If square wave input current control profile is used, then implementation simplicity and winding protection are improved, but torque ripple increases significantly
Solution Approach 1:
The patent applies dynamics by transitioning from a static square wave current profile to a dynamic, continuously adjustable current waveform. The controller dynamically modifies the current profile based on real-time operating conditions, rotor position, and torque requirements, enabling smooth current transitions that minimize torque ripple while maintaining implementation feasibility through programmable control.
Solution Approach 2:
The patent employs parameter changes by continuously varying current magnitude, phase, and timing parameters to optimize torque production. The controller adjusts current waveform parameters in real-time based on feedback from torque sensors and rotor position encoders, transforming the fixed square wave parameters into dynamically optimized parameters that reduce torque ripple while preserving control simplicity.
2Power
If high transient currents are allowed to achieve flat torque output, then torque performance is improved, but winding current rating requirements increase
Solution Approach 1:
The patent applies preliminary action by pre-calculating and pre-limiting current waveforms within safe operating boundaries before they are applied to the motor. The controller uses predetermined current limits and ramp rates that prevent excessive transient currents from occurring in the first place, eliminating the need for oversized windings while ensuring torque requirements are met through optimized current profiles.
Solution Approach 2:
The patent employs feedback mechanisms by continuously monitoring actual torque output and phase currents, then using this information to adjust subsequent current commands. The closed-loop control system detects torque ripple and current deviations in real-time, automatically correcting them by modifying current waveforms to stay within rated limits while maintaining desired torque performance, thus preventing the need for excessive current ratings.
3Loss of energy
If phase current is limited to threshold levels, then heat generation and component rating requirements are reduced, but torque output decreases
Solution Approach 1:
The patent applies merging by combining current from multiple phases and utilizing overlapping active intervals of different phases to compensate for individual phase current limitations. When one phase is current-limited to reduce heat, adjacent phases are coordinated to provide additional torque contribution, merging their effects to maintain overall torque output while keeping individual phase currents within thermal limits.
Solution Approach 2:
The patent employs periodic action by implementing cyclic current modulation and phase switching patterns that distribute torque production across multiple time intervals. Instead of sustaining high current continuously in one phase, the controller uses periodic current pulses and phase rotations that average out to the required torque while keeping instantaneous phase currents below thermal thresholds, reducing heat generation through time-based distribution.
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 reduces torque ripple, minimizes heat generation, and allows the use of lower-rated components, achieving efficient and cost-effective torque output while protecting stator windings from high currents.
Implementation Method 1
an electric motor may be used to convert electrical power stored within a common bus or storage device into mechanical power
Data Source
AI summary
A method of controlling an electric motor may include determining a desired torque at the electric motor. A current at a first phase of the electric motor may be calculated at a controller. The calculated current may be a current that results in supplying the desired torque at the electric motor. The controller may compare the calculated current to a predetermined threshold current, and when the calculated current is greater than the predetermined threshold current, the controller may reduce the calculated current to the predetermined threshold current and adjust a current in a second phase adjacent to the first phase of the electric motor to continue to supply the desired torque at the electric motor.