The CD Automation REVO-S is a three-phase thyristor static relay designed to replace electromechanical contactors in resistive heating applications. Covering 3.5 A to 800 A at up to 600 V (690 V optional from 60 A upward), it switches heating elements silently and without contact wear, using zero-crossing burst-fire control to minimise EMC while delivering precise average power to the load. The compact DIN-rail form factor makes it suited for multi-zone control panels where space per channel is limited.

How does burst-fire control differ from phase-angle firing in the REVO-S?

The REVO-S uses zero-crossing burst-fire (also called cycle-skipping or half-cycle modulation). The thyristor switches ON only at the voltage zero-crossing point, conducting complete half-cycles to the load. By varying the number of ON half-cycles within a fixed cycle period (4, 8, or 16 cycles at 50% power demand), the controller adjusts average power without the harmonic distortion and EMI generated by phase-angle firing. This makes the REVO-S suitable for resistive loads with long thermal time constants — heating elements, infrared lamps (medium/long wave), and transformerless resistance banks — where fast cycle-by-cycle regulation is unnecessary.

What input signals can drive the REVO-S?

In its standard configuration, the REVO-S accepts a 4–30 V DC SSR (solid-state relay) signal directly from any temperature controller, PLC digital output, or panel switch. An optional TU-E adaptor module adds an analogue input — 0–10 V DC or 4–20 mA — for applications where the upstream controller provides a proportional signal rather than a discrete SSR output. No external power supply is required for the firing circuit; the unit derives its control power from the input signal itself.

What protection and diagnostics are available?

Internal ultra-fast semiconductor fuses are fitted as standard from 60 A upward (optional on 30–40 A units), protecting the thyristors against short-circuit faults. The optional Heater Break Alarm (HBA) continuously monitors load current and diagnoses partial or total heating element failure, open-circuit wiring, and SCR short-circuit conditions. Units from 225 A incorporate fan cooling (standard 230 V fan, 115 V optional). An internal thermal switch protects against over-temperature by inhibiting firing if the heat-sink exceeds safe limits.