Brushless Bi-Directional Electric Machine Speed Adaptation
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Solution Overview
Problem
Existing electric machines, such as crank assist motor generator units (CAGU), face challenges in optimizing performance across different rotational speeds when switching between motor and generator modes, leading to back EMFs and heat production, particularly in vehicles where optimal speeds for motor and generator operations differ.
Innovation Solution
A brushless bi-directional electric machine design featuring a rotor with a central part and peripheral structure, stationary exciting coils, and a stator with windings, controlled by an inverter controller that adjusts current flow through the coils to optimize magnetic field strength and reduce back EMFs across varying speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the machine is optimised to function as a generator with maximum generation at maximum rotational speed, then generator performance is improved, but motor performance deteriorates (optimised for low speed only)
Solution Approach 1:
The patent employs a switched reluctance machine design where the magnetic circuit characteristics can be dynamically changed by switching different stator winding configurations. This allows the machine to adapt its optimal operating speed range between motor and generator modes, resolving the contradiction between optimized generator performance and motor speed adaptability.
Solution Approach 2:
The invention changes the electrical parameters of the machine by switching between different stator winding connections (series/parallel configurations). This parameter switching enables the machine to maintain optimal performance across different speed ranges for both motor and generator operations, rather than being fixed for a single optimal speed.
2Adaptability or versatility
If the machine operates outside its optimised speed range, then speed adaptability is improved, but back EMFs are generated causing heat production
Solution Approach 1:
The switched reluctance machine dynamically adjusts its magnetic circuit configuration through winding switching, allowing the optimal speed range to shift according to operating conditions. This dynamic adaptation prevents operation outside the optimized range, thereby reducing back EMF generation and associated heat production.
Solution Approach 2:
The patent creates multiple equivalent magnetic circuit configurations through winding switching, effectively copying the optimal operating characteristics to different speed ranges. This allows the machine to maintain efficient operation across a broader speed range without generating excessive back EMFs and heat.
3Reliability
If field weakening currents are introduced to prevent damage at high speeds, then machine protection is improved, but device complexity increases
Solution Approach 1:
The switched reluctance machine uses dynamic winding switching to adjust magnetic circuit characteristics, providing inherent protection against high-speed damage without requiring additional field weakening control systems. This reduces device complexity while maintaining reliability.
Solution Approach 2:
The machine protects itself from high-speed damage through automatic winding configuration switching based on operating conditions, eliminating the need for external field weakening control systems. The system self-regulates to prevent damage while simplifying the overall control architecture.
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 solution enables the electric machine to efficiently operate both as a motor and generator by dynamically controlling the exciting current, reducing back EMFs and heat production, thus maintaining performance across a wide range of speeds without the need for field weakening currents.
Implementation Method 1
brushless alternating current electric machines where the magnetic field is created by a coil through which a current passes
Implementation Method 2
a controller configured to control an exciting current supplied to the windings of the exciting coils
Data Source
AI summary
A brushless bi-directional electric machine comprises a housing mounting exciting coils, a rotor and a stator, the exciting coils and the stator being stationary with respect to the housing and the rotor mounted for rotation with respect to the housing. The electric machine comprises a controller configured to control an exciting current supplied to the exciting coils.