Thyro Family (SCR power controller products)

Choose Thyro-S when the application primarily needs repeatable on/off switching rather than continuously regulated voltage, current or power. Thyro-A adds TAKT, VAR and QTM operation with ratings from 8 to 1500 A, making it suitable for a broad range of conventional heating systems. Thyro-A+ adds higher measurement accuracy, an optional display and more flexible commissioning, while the current range extends to 650 A. Thyro-PX is intended for more demanding systems requiring up to 5000 A, up to 1000 V, multi-zone control or VSC operation. Thyro-XD is the specialised 30 A choice where compact construction, resistance-change detection and ±0.5% power accuracy are important.

The firing mode should be selected from the electrical behaviour of the load, the acceptable harmonic content and the process response required. TAKT applies complete mains cycles and is commonly used with resistive loads where slower power modulation is acceptable. VAR controls each sinusoidal half-wave and is useful for transformer loads, rapid ramps and loads whose resistance changes considerably with temperature. QTM provides fast half-wave package control for suitable resistive loads, while VT combines or varies full-wave behaviour to address dynamic thermal processes. Thyro-PX VSC operation can reduce the disadvantages associated with conventional phase-angle control in compatible transformer and variable-resistance applications.

Accuracy varies materially between the series and should be matched to the stability required by the process. Thyro-A provides ±3% voltage accuracy and ±1.5% current accuracy, while Thyro-A+ improves both voltage and current control to approximately ±1.5%. Thyro-PX provides ±0.5% voltage or current control and ±1% power control. Thyro-XD narrows this further to ±0.25% for voltage or current and ±0.5% for power, subject to the stated phase-angle setpoint condition. For processes such as rapid thermal annealing or lamp heating, this difference affects how quickly the system can detect and compensate for changes in load resistance or incoming voltage.

Digital integration is available through EtherNet/IP, EtherCAT, PROFIBUS, PROFINET and Modbus TCP/IP, although the interface arrangement depends on the selected controller. Thyro-S and Thyro-A normally use a shared bus module, which can connect up to eight compatible power controllers under one module. Thyro-A+, Thyro-PX, Thyro-PX DC and Thyro-XD offer broader interface and accessory arrangements, including configurable analogue I/O and local USB access. The analogue setpoint ranges commonly include 0/4 to 20 mA, 0/1 to 5 V and 0/2 to 10 V. Engineers should confirm the network module, controller firmware and required process-data mapping before finalising the automation architecture.

The choice depends on the heater connection, whether a neutral conductor is present and how much independent phase control is required. Two-phase controllers can regulate a three-phase economic circuit using a delta load or a star-connected load without neutral, reducing the number of controlled power paths. A three-phase controller is appropriate where the circuit uses a neutral, open delta or another arrangement requiring control of all three phases. Thyro-S, Thyro-A, Thyro-A+ and Thyro-PX are available in one-, two- and three-phase forms, while Thyro-XD is currently a single-phase 30 A unit. The exact circuit topology must be checked against the model code before ordering or preparing the panel wiring.

Mains load optimisation coordinates the switching of several controllers so that their power demand is distributed rather than applied simultaneously. The dASM arrangement can coordinate groups of up to 32 supported controllers, with up to eight controllers connected to each bus module. This function is intended for TAKT full-wave switching systems and can help limit mains loading, flicker and coincident demand peaks. Thyro-PX also provides digital mains-load optimisation and power monitoring within its broader control architecture. In practice, the designer must consider the number of zones, response time, communication layout and load duty cycles before deciding whether local controller coordination or a wider plant-level power-management strategy is appropriate.

Rated current assumes the environmental and cooling conditions defined for the selected model, so panel thermal design cannot be based on current alone. Several air-cooled variants reach rated current at up to 35°C with forced cooling or 45°C with passive convection, with derating required above the stated limits. The modular water-cooled stack supports up to 690 V AC and approximately 4000 A per stack, but its capability depends on thyristor selection, coolant temperature, flow rate and plumbing arrangement. Each water-cooled thyristor requires up to 10 litres per minute, and the thermal switches open at 85°C. Clearance, semiconductor fusing, conductor sizing, protective earthing and safe isolation must therefore be designed for the complete assembled system.