Switch Control Device SCR Relay Activation Timing
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Solution Overview
Problem
Switch devices with silicon controlled rectifiers (SCRs) are prone to damage due to the SCRs being turned on before the corresponding relays, leading to potential voltage drops and arc discharges.
Innovation Solution
A switch control device with a detection unit and processor that senses input voltage zero crossover or peak signals to determine a delay time for turning on relays, ensuring SCRs are not activated until the relays are operational, thereby reducing voltage drops and arc discharges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the switch device uses an SCR coupled in parallel with relays to control power switching, then the device can achieve power transmission functionality, but the SCR may turn on before the relay is operational causing damage to the switch device
Solution Approach 1:
The control circuit generates a control signal that activates the relay coil before triggering the SCR. This preliminary action ensures the relay switch is already closed and operational before the SCR turns on, preventing the harmful condition where the SCR conducts current through an open relay switch. The timing controller coordinates the activation sequence to ensure relay closure precedes SCR conduction.
Solution Approach 2:
The control circuit monitors the state of the relay switch and uses this feedback to determine when it is safe to activate the SCR. The system waits for confirmation that the relay is properly closed before enabling the SCR, creating a feedback loop that prevents premature SCR activation and potential damage.
2Productivity
If the SCR is activated without ensuring relay operational status, then power switching can occur, but voltage drops and arc discharges may occur causing potential damage
Solution Approach 1:
The system performs preliminary verification that the relay switch is closed before activating the SCR. This preliminary action prevents voltage drops and arc discharges by ensuring the current path is already established through the closed relay contacts before the SCR begins conducting power switching current.
Solution Approach 2:
The control circuit creates a protective condition by ensuring the relay is operational before SCR activation. This beforehand cushioning prevents the harmful effects of voltage drops and arc discharges by preparing the circuit path in advance, cushioning against potential damage from improper switching conditions.
Data Source
AI summary
A switch control device includes a switch device and a control device. The switch device includes first and second input terminals, an output terminal, a processor, and a plurality of delays. The processor is configured to detect period of an input voltage from the first input terminal, and to determine whether the input voltage is normal. A delay time can be computed by the processor, according to the period of the input voltage and a release time of the each delay. If the input voltage from the first input terminal is abnormal, the processor detects a zero voltage crossing signal or a peak of voltage signal, and delays the zero voltage crossover signal or the peak of voltage signal for a delay time, to control the delays coupled to the first input terminal to turn on.