Electric Motor Controller Torque Limiting via DC Link Current Sensing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Electric motors face challenges in managing current and voltage limits to prevent damage, as excessive current can harm the motor, motor controller, and power supply, affecting resource usage and drive feel.
Innovation Solution
A method and apparatus for controlling an electric motor by setting and adjusting torque, speed, DC link current, and voltage limits, using a controller that senses parameters and adjusts torque demands to stay within defined limits, incorporating a cascade structure with regulators for electrical and mechanical parameters to ensure safe operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the electric motor is controlled to deliver high torque and current to improve performance, then power output is improved, but the risk of damage to the motor, motor controller and power supply increases
Solution Approach 1:
The controller pre-establishes current and voltage limits based on the motor's rated parameters before operation begins. These limits are stored as threshold values that the control algorithm continuously monitors, allowing the system to prevent damaging conditions before they occur rather than reacting after damage has been done.
Solution Approach 2:
The control algorithm continuously monitors the actual current and voltage drawn by the motor during operation and compares these values against the pre-set limits. When approaching the limits, the controller automatically adjusts the torque demand to keep operating parameters within safe boundaries, providing real-time feedback control that prevents damage while maximizing power output.
2Power
If the current drawn by the electric motor is increased to improve torque output, then power output is improved, but the electric motor, motor controller and power supply may be damaged
Solution Approach 1:
The controller dynamically adjusts the current parameter by modifying the torque demand sent to the motor based on real-time monitoring of actual current draw. When current approaches the rated limit, the controller reduces the torque demand to maintain current within safe operating boundaries, effectively changing the current parameter to prevent damage while preserving as much power output as possible.
3Productivity
If the torque demand is increased to improve acceleration and performance, then productivity is improved, but the DC link current and voltage limits may be exceeded causing damage
Solution Approach 1:
The control algorithm dynamically adjusts the torque demand in real-time based on the actual operating conditions, including DC link current and voltage levels. Rather than using a fixed torque profile, the system continuously adapts the torque demand to match the actual capacity of the electrical components, allowing maximum acceleration performance while preventing exceedance of electrical limits.
Data Source
AI summary
A method for controlling an electric motor is described herein. The method comprises setting a current limit, a speed limit and a torque limit. The method also comprises sensing a DC link current, comparing the sensed DC link current with the current limit and adjusting the torque limit based on the comparison with the current limit to provide an adjusted torque limit. The method also comprises sensing the speed of the electric motor, comparing the speed with the speed limit and further adjusting the adjusted torque limit based on the comparison with the speed limit.