Relay Zero-Crossing Calibration via Temperature Polynomial
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Solution Overview
Problem
Existing relay control systems face challenges in precisely switching relays at zero-crossing points due to relay delay variations with age and temperature, leading to arcing and contact degradation, and require complex and costly circuitry to account for these changes.
Innovation Solution
A method and system that calibrate relay devices using a master polynomial to account for relay switching delays as a function of temperature, allowing for accurate zero-crossing switching without additional circuitry, by measuring delays at multiple temperatures, deriving a polynomial model, and using it to determine the y-intercept for each relay device, enabling precise timing of relay operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If relay switching delay is not compensated for temperature variations, then relay switching occurs at incorrect timing points, but adding complex temperature compensation circuitry increases device complexity and cost
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing delay compensation values in a lookup table before runtime. During operation, the system simply retrieves the pre-computed delay value based on measured temperature, avoiding complex real-time calculations and reducing runtime computational complexity while maintaining precise temperature compensation for relay switching timing
Solution Approach 2:
The patent replaces complex analog temperature compensation circuitry with a digital processing approach. Instead of using hardware circuits to automatically compensate for temperature effects, the system uses a microprocessor to measure temperature, retrieve pre-computed delay values from a lookup table, and calculate the corrected switching time digitally, thereby reducing overall device complexity
2Speed
If relay switching occurs away from zero-crossing points, then switching speed is improved, but contact erosion increases due to arcing
Solution Approach 1:
The patent applies feedback by continuously monitoring the actual relay switching time and comparing it with the target zero-crossing timing. Based on this feedback and the measured temperature, the system adjusts the trigger timing to ensure the relay switches as close to the zero-crossing point as possible, thereby minimizing arcing and contact erosion while maintaining reliable operation
Solution Approach 2:
The patent changes the timing parameter dynamically based on temperature. By adjusting the trigger time offset from the zero-crossing point according to temperature-dependent relay delay characteristics, the system ensures that switching always occurs at the optimal moment (as close to zero-crossing as possible) regardless of temperature variations, thus protecting contact lifespan
3Measurement precision
If relay delay calibration is performed for each individual relay, then switching precision is improved, but manufacturing time and cost increase
Solution Approach 1:
The patent applies segmentation by dividing the calibration process into two independent stages: a pre-calibration stage where temperature-delay characteristics are measured and stored in a lookup table, and a runtime stage where individual relay delays are compensated using the pre-prepared data. This segmentation allows bulk pre-processing of calibration data, enabling fast individual relay calibration during manufacturing without bottlenecking production throughput
Solution Approach 2:
The patent applies preliminary action by pre-computing and storing delay compensation values in a lookup table before individual relay calibration is needed. This preliminary preparation of calibration data allows each relay to be quickly calibrated during manufacturing by simply retrieving the appropriate delay value from the pre-computed table, rather than performing time-consuming measurements for each relay, thus maintaining high manufacturing throughput
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 approach simplifies and reduces the cost of relay control circuitry while providing accurate temperature-dependent delay determinations, ensuring reliable and efficient switching at zero-crossing points, thereby extending relay lifespan and reducing arcing issues.
Implementation Method 1
A relay may consist basically of an electromagnet with a soft iron bar, called an armature, held close to it. When the electromagnet is energized, it exerts a force on the armature that overcomes the pull of the spring and moves the contact to either complete or break a circuit.
Implementation Method 2
Since the actuation of a relay requires the physical movement of one of the contact electrodes, there may be some delay from the issuance of a close command until the magnetic field has built to a sufficient level to begin movement of the contact electrodes by overcoming the spring force.
Data Source
AI summary
This disclosure describes systems, methods, and apparatus for determining a relay delay for a relay of a relay device used to switch AC power to and from a load. The relay delay can be pre-determined as a model or polynomial including variables for temperature and age, such that the switching instructions can be sent to the rely a relay delay before a zero crossing of the AC signal that the relay is switching, and where the relay delay accounts for temperature and age of the relay in real time or near real time.