Motor Controller Torque Stability with Reduced Capacitance
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Solution Overview
Problem
Existing electric motor systems with high capacitance capacitors are bulky, expensive, and reduce motor lifespan, leading to varying motor phase current and torque production that is sensitive to input voltage and frequency, making it difficult to maintain constant average torque performance.
Innovation Solution
A motor controller system that includes a rectifier, inverter, and a controller configured to estimate torque using instantaneous motor current measurements and generate a real-time current demand signal to produce a substantially constant average motor output torque over a wide speed range, utilizing reduced capacitance capacitors to minimize size and cost while maintaining efficient torque production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If high capacitance capacitors are used in the motor controller, then the energy storage capacity is improved, but the size, cost, and lifespan of the motor controller deteriorate
Solution Approach 1:
The patent changes the capacitance parameter from high to low values, using capacitors with substantially reduced capacitance (e.g., from several hundred μF to much lower values). This parameter change directly reduces the size and cost of the motor controller while the control algorithm compensates for the reduced energy storage capacity to maintain acceptable performance.
2Use of energy by moving object
If high capacitance capacitors are used in the motor controller, then the energy storage capacity is improved, but the cost and lifespan of the motor controller deteriorate
Solution Approach 1:
The patent changes the capacitance parameter to substantially reduced values, eliminating or minimizing the use of large electrolytic capacitors that have limited lifespan. This parameter change improves reliability and lifespan while the control system compensates for the reduced energy storage capability.
3Weight of stationary object
If reduced capacitance capacitors are used in the motor controller, then the size and cost are reduced, but the torque production stability deteriorates
Solution Approach 1:
The patent implements a feedback control algorithm that continuously monitors motor phase currents and adjusts the inverter switching signals to compensate for the reduced capacitance effects. This feedback mechanism maintains torque production stability despite the smaller capacitor size by dynamically adjusting control parameters based on actual system performance.
Solution Approach 2:
The patent changes the capacitance parameter to reduced values and simultaneously adjusts control algorithm parameters to compensate. The control system modifies current demand signals and switching patterns to maintain stable torque production with the reduced energy storage capacity.
4Weight of stationary object
If reduced capacitance capacitors are used in the motor controller, then the size and cost are reduced, but the constant average torque performance deteriorates
Solution Approach 1:
The patent uses feedback control to monitor motor performance and adjust control signals in real-time, compensating for the reduced capacitance effects. This maintains constant average torque performance by dynamically adjusting the inverter switching based on actual motor phase current measurements and estimated torque values.
Solution Approach 2:
The patent changes the capacitance parameter to reduced values and implements corresponding changes in control algorithm parameters, including real-time current demand signal generation and torque estimation adjustments, to maintain constant average torque performance across varying operating conditions.
5Device complexity
If typical control algorithms are used with reduced capacitance capacitors, then the control simplicity is maintained, but the torque production variability increases
Solution Approach 1:
The patent implements a feedback control algorithm that estimates torque from motor phase currents and uses this information to generate adjusted current demand signals. This feedback mechanism maintains torque production consistency without requiring overly complex control logic, achieving a balance between simplicity and performance.
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
The system achieves constant average torque production across varying speed ranges and input voltages, reducing the need for bulky electrolytic capacitors and enhancing motor efficiency and reliability, while providing cost savings by eliminating high-capacitance components.
Implementation Method 1
a rectifier configured to convert an AC input voltage to a pulsing DC voltage
Implementation Method 2
an inverter electrically coupled to the DC link and configured to generate a three phase AC voltage to drive the electric motor
Implementation Method 3
estimate a torque generated in the electric motor using the received measurement of the instantaneous motor current values
Data Source
AI summary
A system and method of controlling an electric motor using a motor controller are provided. The system includes an electric motor controller configured to be coupled to an electric motor and to control the electric motor to produce approximately constant average torque. The controller includes a rectifier configured to convert an AC input voltage to a pulsing DC voltage, a DC link electrically coupled to the rectifier, an inverter electrically coupled to the DC link and configured to generate a three phase AC voltage to drive the electric motor, and a controller configured to receive a measurement of a motor current value for the motor, estimate a torque generated in the electric motor using the measurement of the instantaneous motor current value, and generate a real-time current demand signal using the estimated torque value, the real-time current demand signal compensating the motor controller to produce a substantially constant average motor output torque.