Irrigation Controller AC Switching Overvoltage Protection
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Solution Overview
Problem
The rising manufacturing costs of irrigation controllers due to assembly and component costs, exacerbated by the need for additional protections against power surges and overvoltages such as those from lightning strikes, have not been effectively addressed by conventional technologies.
Innovation Solution
Incorporating a live AC line, an AC common line, AC switching devices, and an impedance element with inductive reactance and resistive components on the AC common line to enhance overvoltage protection, allowing the use of lower-rated components while maintaining effective surge protection, and integrating protection circuitry within AC switches to reduce the need for additional external protection devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If higher-rated AC switching devices with additional protection circuitry are used, then overvoltage protection is improved, but component cost and assembly cost increase
Solution Approach 1:
A surge protection circuit is introduced as an intermediary component between the AC power source and the AC switching devices. This circuit includes a surge protection device (such as a metal oxide varistor) that diverts voltage surges to ground, protecting the AC switching devices from overvoltage damage. By placing this intermediary protection layer, the system can use lower-rated, less expensive AC switching devices while maintaining the same level of overvoltage protection as would be required with higher-rated devices.
Solution Approach 2:
The invention uses a dedicated surge protection device that is designed to be replaced rather than protecting expensive AC switching devices. The surge protection circuit acts as a sacrificial element that absorbs the cost of failure, allowing the use of cheaper AC switching devices. When the surge protection device fails, it can be replaced without replacing the entire AC switching device assembly, reducing overall system cost.
2Reliability
If additional protection devices are added to protect against power surges, then reliability is improved, but device complexity increases
Solution Approach 1:
The surge protection functionality is merged with the existing AC common line infrastructure. The surge protection device is connected in parallel with the AC common line, utilizing the existing grounding path. This merging approach allows the surge protection function to be added without requiring separate dedicated protection circuits for each AC switching device, thereby reducing overall system complexity while maintaining comprehensive protection.
3Ease of manufacture
If lower-rated AC switching devices are used, then component cost is reduced, but tolerance to overvoltage conditions deteriorates
Solution Approach 1:
The surge protection circuit provides beforehand cushioning by absorbing and diverting voltage surges before they can reach the AC switching devices. The metal oxide varistor or similar surge protection device is positioned upstream in the circuit, creating a protective buffer that limits the maximum voltage that can appear across the AC switching devices. This prior cushioning allows the use of lower-rated AC switching devices that would otherwise be vulnerable to overvoltage damage.
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 solution reduces the cost of components and assembly by enabling the use of lower-rated components while achieving the same level of protection as higher-rated systems, simplifying manufacturing, and improving tolerance to overvoltages and surges, thus reducing labor and material costs.
Implementation Method 1
an impedance element (132) coupled serially on the AC common line with the transformer, wherein the impedance element comprises an inductive reactance and a resistive component
Implementation Method 2
a plurality of AC switching devices coupled with the live AC line, wherein the plurality of AC switching devices are configured to selectively pass the AC power signal to one or more valve solenoids
Data Source
AI summary
Some embodiments provide irrigation controllers, comprising: a transformer configured to step down a voltage producing an AC power signal; a live AC line and an AC common line coupled with the transformer; a plurality of AC switches coupled with the live AC line and configured to selectively pass the AC power signal to one or more valve solenoids such that the one or more valve solenoids are effectively coupled across the live AC line and the AC common line; an impedance element coupled serially on the AC common line with the transformer, wherein the impedance element comprises an inductive reactance and a resistive component, and the impedance element is configured to increase overvoltage protection between the transformer and the plurality of AC switches increasing an effective voltage tolerance to the overvoltage conditions at the AC switches; and a controller configured to selectively control the plurality of AC switches.