Three-Phase Open-Phase Detection Using Photocoupler Pulse Logic
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Solution Overview
Problem
Existing methods for detecting open phases and interruptions in three-phase AC power supplies are inefficient, requiring time-consuming adjustments to circuit elements and experiencing delayed detection responses due to the need for voltage adjustments and the presence of smoothing capacitors.
Innovation Solution
A detection device using three photocouplers connected between phases of a three-phase AC power supply, with a controller performing an AND operation on pulse detection signals to quickly determine the presence of open phases or interruptions, and adjusting counters to differentiate between normal states and anomalies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If photocouplers are connected between phases of a three-phase AC power supply to detect open phases, then open phase detection capability is achieved, but time-consuming adjustments to circuit elements and threshold settings are required
Solution Approach 1:
The detection device automatically determines open phases by having the controller perform AND operations on pulse detection signals from three photocouplers, eliminating the need for manual adjustment of circuit elements and threshold settings. The system self-configures by processing the logical relationship between phase signals.
Solution Approach 2:
The invention changes the detection parameter from manual threshold voltage adjustment to automated logical operation on pulse signals. The controller uses AND operations on inverted pulse detection signals to automatically determine open phase conditions without requiring manual parameter tuning.
2Stability of the object's composition
If a smoothing capacitor is connected in parallel to the rectifier circuit to detect interruption, then detection stability is improved, but detection response is delayed until capacitor voltage becomes zero
Solution Approach 1:
The invention extracts the detection function from the smoothing capacitor circuit by using photocouplers connected directly to the AC power supply phases. This separates the detection path from the power processing path, allowing immediate detection without waiting for capacitor discharge.
Solution Approach 2:
The photocoupler acts as an intermediary device that optically couples the detection circuit to the power supply phases without requiring direct electrical connection through the rectifier and capacitor. This enables fast response while maintaining isolation and stability.
3Measurement precision
If multiple detection circuits (electromagnetic contactor and single-phase detection circuit) are combined to detect open phases, then detection accuracy is improved, but device complexity increases
Solution Approach 1:
The invention merges the functionality of multiple detection circuits into a single integrated system where three photocouplers and a controller work together. The controller performs logical operations on signals from all three photocouplers to simultaneously determine both open phase conditions and which specific phase is open, reducing overall system complexity.
Solution Approach 2:
The controller serves multiple functions: it receives pulse detection signals from three photocouplers, performs AND operations on inverted signals to detect open phases, and identifies which specific phase is open. This multi-functionality replaces the need for separate specialized circuits.
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 time and labor required for detecting open phases and interruptions, allowing for rapid identification without the need for extensive circuit adjustments and minimizing detection delays.
Implementation Method 1
A light emitting element of this photocoupler emits light when a normal voltage is supplied
Implementation Method 2
when the light receiving element of the photocoupler is turned on, a pulse detection signal is output
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
There are provided a three-phase AC power supply that outputs AC voltages in LI, L2, L3 phases, photocouplers that are connected to respective lines between the L1 phase and the L2 phase, the L2 phase and the L3 phase, and the L3 phase and the L1 phase of the three-phase AC power supply, and convert respective line voltages of the L1 phase and the L2 phase, the L2 phase and the L3 phase, and the L3 phase and the L1 phase of the three-phase AC power supply into a pulse detection signal, a light receiving element of the photocoupler that is set to turn on at a predetermined threshold voltage or higher, and a controller that performs an AND operation of each pulse detection signal to generate an AND operation pulse, and determines presence or absence of an open phase and interruption and which of the L1 phase, L2 phase, and L3 phase is the open phase when the open phase is present by each pulse detection signal and the AND calculation pulse.