Electric Machine Winding Excitation Using Fixed Advance Time
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Solution Overview
Problem
As the rotor of an electric machine accelerates, the increasing back emf makes it difficult to drive power into the machine, requiring complex on-the-fly calculations to adjust the excitation timing, and existing methods struggle to maintain efficient power delivery across varying speeds and voltages.
Innovation Solution
A method of controlling the electric machine by exciting the winding a fixed advance time ahead of back emf zero-crossings, with the advance time increasing with rotor speed and varying with excitation voltage, allowing for consistent power delivery without the need for on-the-fly calculations, and incorporating a freewheeling phase to manage current spikes and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the advance angle is increased with rotor speed to overcome back emf, then power delivery is improved, but control complexity increases due to required on-the-fly calculations
Solution Approach 1:
The patent changes the control parameter from advance angle to advance time. By using a fixed advance time regardless of rotor speed, the system maintains effective power delivery while eliminating the need for complex real-time calculations of advance angle based on speed and frequency.
Solution Approach 2:
The patent extracts the calculation burden from the control system by removing the dependency on real-time speed and frequency measurements. The fixed advance time approach takes out the complex trigonometric calculations that would otherwise be required to determine the appropriate advance angle at each operating point.
2Use of energy by moving object
If excitation voltage is reduced, then energy consumption is decreased, but power delivery capability deteriorates
Solution Approach 1:
The patent applies preliminary action by exciting the winding in advance of the back emf zero-crossings by a fixed time period. This advance excitation ensures that current is established before the back emf opposes it, maintaining effective power delivery even at lower excitation voltages where the back emf is less dominant.
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 ensures efficient power delivery into the electric machine as it accelerates, maintains output power across a range of speeds and voltages, and simplifies control by eliminating the need for complex calculations, while preventing current spikes and improving waveform smoothness.
Implementation Method 1
As the permanent-magnet rotor of an electric machine rotates, it induces a back emf in a winding of the electric machine
Data Source
AI summary
A method of controlling an electric machine that includes exciting a winding of the electric machine in advance of zero-crossings of back emf by a fixed advance time over a range of speeds. Additionally, a control system for an electric machine, and a product incorporating the control system and electric machine.