Overview

The JLFK series combination switch consists of three independent combination switches, suitable for controlling the on/off of low-voltage reactive power compensation capacitor banks. The basic operating principle of the combination switch is to connect a thyristor (SCR) in parallel with a magnetic latching relay.

This allows the combination switch to have the advantages of SCR zero-crossing switching during the instant of connection and disconnection, while also having the power-saving advantages of a contactor switch during normal connection.

Conventional combination switches are controlled by DC voltage, with unidirectional signal transmission. Each combination switch requires a separate control signal line.

If a combination switch malfunctions, the controller or distribution terminal will not be aware of it, potentially causing the compensation device to operate with the malfunction for extended periods.

The introduction of the intelligent combination switch effectively resolves this problem. It transmits fault information to the host computer via a communication line, allowing users to immediately understand the cause of any compensation device anomalies. This is more in line with the spirit of smart grid development. Furthermore, all control circuits are connected in parallel by a single twisted-pair cable, significantly reducing the number of control lines required for the compensation device.

Features

◆ Zero-Crossing Switching: The basic operating principle of the combination switch is to connect a thyristor (SCR) switch and a magnetic latching breaker in parallel, achieving zero-crossing voltage conduction and zero-crossing current disconnection. This combination switch combines the advantages of a thyristor switch, namely zero inrush current, with the power-saving advantages of a physical switch during normal operation. This is achieved by controlling the thyristor to conduct first at the instant the voltage crosses zero, and then closing the magnetic latching breaker after the voltage stabilizes. During zero-crossing switching, the magnetic latching breaker is opened first, and the thyristor is delayed to disconnect after zero-crossing, thus achieving zero-crossing current disconnection.

◆ A single-chip microcomputer controls switching and intelligently monitors the operating status of the thyristor, magnetic latching breaker, input power supply, and load, providing comprehensive protection. Voltage Fault Phase Loss Protection: The switch refuses to close when a system voltage phase is lost. Power Supply Phase Loss Protection: The switch refuses to close when a power phase is lost. Self-Diagnostic Fault Protection: The system automatically monitors the operating status of the thyristor (SCR) and magnetic latching circuit breakers. If a fault occurs, the switch refuses to close or automatically switches off. Power Failure Protection: The switch automatically trips and switches off in the event of a sudden power outage after connection.

◆ No Harmonic Injection: Since the thyristor's zero crossing triggers the switch-on moment, followed by a delay when the magnetic latching circuit breaker closes, the circuit breaker generates no harmonics during operation.

◆ Low Power Consumption: Due to the use of a magnetic latching circuit breaker, the control device consumes power only at the moment of switching, not at other times. Furthermore, the magnetic latching circuit breaker has low contact resistance and generates no heat, eliminating the need for external heat sinks or fans, reducing costs. This completely prevents the burning of the SCR and poses no risk to other electrical equipment operating on the same unit, truly achieving energy savings and consumption reduction.

◆ Optoelectronic isolation between the input signal and the composite switch; strong anti-interference capability, safe and reliable operation.

Specifications