High-speed electric system
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Solution Overview
Problem
Single-phase permanent-magnet electric machines face challenges in driving current and power at high speeds due to increasing back emf and high rotor losses, which are typically addressed by using multi-phase machines, increasing system cost.
Innovation Solution
A control system for a single-phase permanent-magnet electric machine that sequentially excites and freewheels the winding, varying the excitation and freewheel times to maintain efficiency and output power over a wide speed range, allowing high-speed operation with efficiency of at least 80% and constant output power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single-phase permanent-magnet electric machine is used, then system cost is reduced, but the machine cannot operate efficiently at high speeds due to increasing back emf and rotor losses
Solution Approach 1:
The patent applies dynamic control by varying the excitation timing (advance angle) and freewheeling duration based on operating speed. The control system dynamically adjusts these parameters to maintain optimal performance across a wide speed range (60-100+ krpm), transforming the static single-phase machine into a dynamically adaptable system that overcomes the inherent back emf limitation at high speeds
Solution Approach 2:
The patent changes key operating parameters including excitation voltage, excitation timing (advance angle), and freewheeling time to enable high-speed operation. By adjusting these parameters dynamically, the system maintains efficiency above 80% while operating at speeds exceeding 60 krpm, effectively resolving the contradiction between single-phase simplicity and high-speed capability
2Ease of manufacture
If a single-phase permanent-magnet electric machine is used, then system cost is reduced, but efficiency drops at high speeds due to back emf and rotor losses
Solution Approach 1:
The control system performs preliminary action by exciting the winding in advance of the back emf zero-crossing (advance angle excitation). This timing strategy ensures that current is established in the winding before the back emf opposes it, thereby reducing rotor losses and maintaining efficiency at high speeds while keeping the system cost-effective
Solution Approach 2:
The patent employs periodic excitation and freewheeling cycles, where each electrical half-cycle includes a drive period (winding excitation) followed by a freewheel period. This periodic action pattern, with duty cycles adjusted according to speed, minimizes energy losses by ensuring the winding is excited only when it contributes effectively to torque production
3Speed
If multi-phase machines are used to achieve high-speed operation, then speed and efficiency are improved, but system cost increases
Solution Approach 1:
The patent makes the single-phase winding perform multiple functions by implementing both excitation and freewheeling operations within the same phase. The control system universally manages the single phase to provide torque production, energy recovery, and loss minimization, effectively replacing what would traditionally require multiple phases while reducing system cost
Solution Approach 2:
The control system acts as an intermediary that enables the single-phase machine to achieve multi-phase performance. Through sophisticated timing control of excitation and freewheeling periods, the control system mediates between the limited single-phase hardware and the desired high-speed multi-phase performance, maintaining efficiency above 80% at speeds exceeding 60 krpm
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
Enables high-speed operation of a single-phase permanent-magnet electric machine with high efficiency and constant output power, reducing costs by avoiding the need for additional phases, while maintaining performance across varying loads and battery voltages.
Implementation Method 1
As the speed of the electric machine increases, the back emf in the phase winding increases
Implementation Method 2
single-phase permanent-magnet electric machines are driven by commutating current in a single phase winding
Data Source
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AI summary
An electric system comprising a single-phase permanent -magnet electric machine and a control system for driving the electric machine under load at speeds in excess of 60 krpm. Additionally, a vacuum cleaner comprising the electric system.