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Changhui Instruments has newly launched the YR-ZKH series of single-phase phase-shift triggers and three-phase phase-shift triggers. The Changhui phase-shift trigger utilizes microcontroller-based intelligent technology, offering powerful performance and high reliability; it is suitable for phase control in AC half-controlled and fully controlled bridge circuits such as those using bidirectional thyristors or two reverse-connected unidirectional thyristors. Features of Changhui phase-shift trigger: 1. It adopts a standard 35mm DIN rail mounting method, features an industrial-grade seven-segment LED display, and the panel buttons allow for on-site programming. 2. The input signal can be selected using an internal DIP switch; 4-20mA/0-10mA or 0-5V/1-5V signal inputs are available. 3. Depending on the different application combinations of thyristors, the instrument can be used with the following 4 thyristor combinations: ① Two single-phase thyristors connected in reverse parallel ； ②Single two-way thyristor ； ③A thyristor and a rectifier diode are connected in reverse parallel ； ④Bridge half-controlled rectifier composed of 2 (or 3) unidirectional thyristors and rectifier diodes ； 4. It features an alarm status indicator, allowing the operating condition of the current load to be analyzed through the status light. The status indicator lights include running, limit reached, slightly over, overloaded, balanced, and underbalance. 5. To prevent rapid changes in the phase-shifted output, an output change delay is implemented, which can be adjusted between 5% and 90%. 6. It features current limiting functionality, allowing control of the load through external potentiometer input for current limitation or internal current limitation. 8. It features a phase shift output lower limit protection function, allowing the setting of a minimum phase shift time that can be adjusted within the range of 0.1ms to 2ms. 9. It features a phase-shifted output delay function, suitable for applications where the phase shift is not within the 0-180° range; the output delay time can be adjusted between 0.1ms and 3ms. 10. It can be used in conjunction with various temperature controllers, and is suitable for temperature control in industries such as circuits, kilns, and industrial furnaces. Three-phase four-wire connection and the proper selection of the neutral wire: When the load is a heating furnace and it’s possible that the loads on different phases are not equal (such as in the case of silicon carbide rod furnaces), the three-phase four-wire system provides better balance compared to the three-phase three-wire system. Moreover, when one of the phase loads opens circuit, the three-phase four-wire system can automatically detect this and issue an alarm. Therefore, the three-wire or four-wire system offers better performance than the three-phase three-wire system, but care must be taken to select the neutral wire correctly. In normal applications, if the three-phase load is perfectly balanced, the currents in the neutral wires cancel each other out to 0; therefore, the neutral wires are conventionally made with a much smaller diameter than the phase wires. However, in the case of three-phase four-wire phase-shifting triggering, when the phase shift angle is less than 60°, the current in the neutral wire is equal to the sum of the currents in the three phase wires (as the three-phase load alternates between being active, all the current flows through the neutral wire, and these currents do not cancel each other out). When the phase shift angle is between 60° and 120°, the current in the neutral wire varies between 3 times and 1 time the current in the phase wires. The neutral wire current becomes zero only when the thyristors are fully conductive and the three-phase load is balanced. Therefore, when a regular resistance wire serves as the load, the neutral wire must have the same diameter as the phase wires. For loads whose resistance changes with temperature or aging, such as silicon carbide rod electric furnaces, since they often operate at a small phase shift angle, the neutral wire should be thicker than the phase wires, ideally 2-3 times the safe current-carrying capacity of the phase wires. Not only should the neutral wire from the cabinet to the electric furnace be thick, but also the neutral wire from the cabinet to the power supply transformer should be thick, in order to ensure the safety of the neutral wire and avoid excessive energy loss in it. Regarding the high-frequency interference caused by phase-shift triggering, since this method generates significant interference in the 1–100 kHz frequency range, the phase-shift trigger should be installed close to the thyristor, but at the same time at a certain distance from the power lines. The length of the trigger wires should be kept as short as possible, and it is advisable not to run trigger wires of different phases side by side. Note: Capacitors and resistors for absorption, as well as varistors, should be connected in parallel across both terminals of each thyristor in order to reduce high-frequency interference and protect the thyristors. Library: http://yunrun.com.cn/tech/