Rotary Electrical Machine Switch Failure Protection
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Solution Overview
Problem
Conventional rotary electrical machines face reliability issues due to continuous large field current flow when a short failure occurs in the switch, leading to overheating and reduced reliability, especially when high output is required with low voltage batteries.
Innovation Solution
The design includes a controller that calculates a duty ratio to manage the field winding's inductance and incorporates a relay and abnormality detection to prevent continuous power supply when a short failure is detected, along with a q-axis magnetic circuit with higher permeance than the d-axis circuit to improve torque and power generation capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If continuous large field current is supplied to achieve high output, then power generation capacity is improved, but reliability deteriorates due to overheating when switch failure occurs
Solution Approach 1:
A relay is introduced as an intermediary component between the power source and the field winding. The relay acts as a protective mediator that can interrupt the field current circuit when abnormality is detected, preventing continuous large current flow and overheating while allowing high power operation under normal conditions
Solution Approach 2:
An abnormality detection part monitors the switch state and provides feedback to the relay control. When switch failure is detected, the feedback signal triggers the relay to open the field current circuit, automatically protecting the system from overheating while maintaining high power capability during normal operation
2Power
If q-axis magnetic circuit permeance is increased to improve torque, then power generation capacity is improved, but device complexity increases
Solution Approach 1:
The magnetic pole parts are designed with different local qualities: the q-axis magnetic circuit path has higher permeance characteristics compared to the d-axis path. This is achieved by optimizing the magnetic pole part geometry and material distribution locally, allowing enhanced torque production without requiring complete redesign of the entire magnetic circuit
Solution Approach 2:
The magnetic circuit is designed with asymmetric permeance characteristics where the q-axis permeance is deliberately made larger than the d-axis permeance. This asymmetric design optimizes torque generation by aligning the high permeance axis with the torque-producing magnetic flux path, achieving improved power output without symmetric complexity
3Reliability
If duty ratio is limited to prevent inductance saturation, then reliability is improved, but power output is reduced
Solution Approach 1:
The controller dynamically adjusts the duty ratio based on real-time operating conditions, field current magnitude, and inductance characteristics. By continuously optimizing the duty ratio rather than using a fixed limit, the system maintains field current controllability and prevents inductance saturation while maximizing power output at each operating point
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 configuration enhances the rotary electrical machine's reliability by preventing continuous field current flow during switch failures and improves torque and power generation efficiency by managing inductance and permeance, while maintaining controllability of the field current.
Implementation Method 1
a field winding that is wound on the outer circumferential side of the boss part and generates a magnetomotive force by supplying a field current
Implementation Method 2
a stator core around which an armature winding is wound
Data Source
AI summary
A rotary electrical machine includes a switch for supplying power to a field winding and controller. A ratio of an on-time to one switching cycle of the switch is defined as a duty ratio, and a duty ratio which is larger than the duty ratio corresponding to the field current that gives the maximum reduction amount of the inductance of the field winding with respect to an increasing amount of the field current in a range that the current can take and has a value less than 100% is set as a predetermined value. The controller calculates the duty ratio wherein an upper limit of the ratio is the predetermined value and turns on/off the switch based on the calculated duty ratio. Also, a relay and abnormality detection part that detects abnormality in the switch. The relay is switched to off in response to the occurrence of abnormality being detected.