VAWT Eddy-Current Braking for High-Wind Speed Control
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Solution Overview
Problem
Vertical-axis wind turbines (VAWTs) face challenges in efficiently managing high wind speeds, leading to excessive wear, maintenance costs, and downtime due to the need for complex and costly active blade control systems and friction brakes, which are not well-suited for limiting rotational speed effectively.
Innovation Solution
A lift-type VAWT system incorporating an eddy-current brake and a control system that regulates braking power based on generator operating parameters, allowing operation at higher wind speeds by converting excess energy into heat, reducing wear, and minimizing downtime.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If friction brake is used to prevent generator overload in strong winds, then generator protection is achieved, but brake disc and brake pads overheat after prolonged use requiring standstill
Solution Approach 1:
The patent introduces an eddy-current brake as an intermediary braking mechanism between the friction brake and the generator. This eddy-current brake operates on the primary shaft before the friction brake, serving as a mediator that handles excess energy conversion to heat without subjecting the friction brake components to continuous high-temperature stress, thereby protecting the generator while preventing overheating of the friction brake components.
Solution Approach 2:
The braking system is segmented into two distinct parts: an eddy-current brake for primary braking and energy dissipation, and a friction brake for secondary braking and standstill. This segmentation allows each component to operate within its optimal temperature range, with the eddy-current brake handling the majority of the thermal load during prolonged high-wind conditions.
2Productivity
If active blade control is implemented in VAWTs, then power transfer improvement is achieved, but blade drives experience extreme mechanical loads and wear reducing lifetime
Solution Approach 1:
The patent extracts the pitch control function from the blade drive system. Instead of actively controlling blade pitch to regulate power transfer, the system uses a passive fixed-pitch rotor design where power regulation is achieved through the eddy-current brake on the primary shaft. This extraction eliminates the mechanical wear and extreme loads on the blade drives while maintaining effective power transfer control.
3Reliability
If friction brake is used to limit rotational speed, then generator overload prevention is achieved, but high downtime occurs due to frequent braking to standstill
Solution Approach 1:
The eddy-current brake is activated in advance before the friction brake becomes necessary. By continuously dissipating excess energy through eddy-current braking during high-wind conditions, the system prevents the need for frequent stops to cool the friction brake, thereby reducing downtime while maintaining generator protection.
4Speed
If auxiliary generator is added to absorb power peaks, then rotational speed control is improved, but system complexity increases due to clutch requirements
Solution Approach 1:
The patent replaces the mechanical clutch system required for auxiliary generator connection with an electrical control approach. The eddy-current brake, controlled by an electrical control system, provides rotational speed control without requiring mechanical clutches or auxiliary generators, thereby simplifying the overall system while maintaining effective speed control.
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 VAWTs to operate efficiently and safely in stronger winds by maintaining constant rotational speed, reducing wear, and extending operational time, with the eddy-current brake effectively managing peak wind conditions.
Implementation Method 1
The eddy-current brake comprises a conductive rotor mounted on the secondary shaft and one or more magnets, preferably one or more electromagnets, for inducing eddy currents in the conductive rotor and thus braking the drive train.
Implementation Method 2
one or more electromagnets, for inducing eddy currents in the conductive rotor
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A lift-type VAWT (10), comprises a rotor (12), a generator, a drive train for transmitting mechanical power from the rotor to the generator (20), a braking system including an eddy-current brake (22) and at least one friction brake (24), and a control system (36). The drive train comprises a primary shaft (14) carrying the rotor, a secondary shaft (18) connected to the generator, and a transmission (16) connecting the primary to the secondary shaft. The control system monitors one or more operating parameters of the generator and retards the secondary shaft by regulating the braking power of the eddy-current brake depending on the monitored operating parameters of the generator. The control system further monitors operating parameters of the eddy-current brake and activates the friction brake(s) to bring the rotor to a halt when stopping of the wind turbine is mandated.