Electric Machine Pulse Modulation With Field Weakening
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Solution Overview
Problem
Conventional electric machines face inefficiencies when operating outside their peak efficiency torque regions, particularly in electric vehicles where energy conversion efficiency varies widely with operating conditions.
Innovation Solution
The implementation of modulated pulse control for electric machines, which switches between continuous and pulse modulation modes based on torque demand, shaft speed, and noise, vibration, and harshness (NVH) considerations, to optimize energy efficiency by operating at or near peak efficiency torque levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the electric machine operates in continuous mode to meet torque demand, then the torque output is maintained, but the energy conversion efficiency decreases when operating outside peak efficiency regions
Solution Approach 1:
The patent applies periodic pulsed operation instead of continuous operation. The electric machine is pulsed on and off at frequencies that produce the desired average torque while allowing the machine to operate at peak efficiency during active pulses. This periodic action enables the machine to meet torque demands while spending more time in high-efficiency operating regions, thereby resolving the contradiction between maintaining torque output and improving energy conversion efficiency.
2Loss of energy
If the electric machine operates in pulse modulation mode to improve energy efficiency, then the energy conversion efficiency increases, but the torque output may become insufficient to meet demand
Solution Approach 1:
The patent employs feedback control by continuously monitoring the torque demand and comparing it with the torque produced during pulsed operation. The control system adjusts the duty cycle and pulse frequency based on this feedback to ensure that the average torque output meets the demand while maintaining operation at peak efficiency points. This closed-loop feedback mechanism resolves the contradiction by dynamically optimizing the pulsed operation parameters to satisfy both efficiency and torque requirements.
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 enhances the overall energy conversion efficiency of electric machines by increasing the proportion of operation time within high-efficiency regions, thereby extending the range of battery-powered electric vehicles.
Implementation Method 1
field weakening to mitigate or eliminate generation of a retarding motor torque in situations when Back Electromagnetic Force (BEMF) exceeds a supply voltage
Data Source
AI summary
Modulated pulse control of electric machines to deliver a desired output in a more energy efficient manner by either (a) operating the electric machine in a continuous mode when a requested torque demand is greater than the peak efficiency torque of the electric machine or (b) in a pulsed modulation mode when the requested torque demand is less than the peak efficiency torque of the electric machine. When operating in the pulsed modulation mode, the inverter may be deactivated to further improve the system efficiency when field weakening is not required to mitigate or eliminate generation of a retarding torque in situations when Back Electromagnetic Force (BEMF) exceeds a supply voltage for the inverter of the machine.