The EZ series from Motortronics (Phasetronics) are microprocessor-governed SCR power controllers for three-phase resistive heating and lighting loads. Unlike fixed-time-base burst fire controllers that can cause visible flicker and thermal cycling, the EZ uses a variable time base algorithm — at 50–100% demand, the maximum off period is just 1 AC cycle, delivering smooth, flicker-free power that extends heater element life. Models span EZ1 (single-phase) to EZ3 (three-phase with additional configurations).

How does variable-time-base burst firing differ from fixed-time-base?

In fixed-time-base burst fire, the controller uses a repeating window (e.g., 16 cycles) and fires for N cycles within that window to achieve the desired power percentage. At low demand, this creates long off periods — a heater at 25% power on a 16-cycle base is off for 12 consecutive cycles, causing measurable temperature ripple. The EZ series' variable time base continuously recalculates the optimal on/off pattern: at 50% demand and above, off time is capped at 1 cycle; at 25% demand, the maximum on-to-on cycle interval is 3 cycles. The gate pulse is applied just before the zero-crossing point, firing the SCR at the absolute minimum voltage differential for virtually RFI-free switching. The output resolution is selectable at 16 or 64 steps.

What protection and control features are built in?

Back-to-back SCR pairs in an AC switch configuration with integral MOV (Metal Oxide Varistor) transient protection handle supply-side voltage spikes without external surge suppression. SCR PIV ratings of 1,600 V (up to 100 A) and 1,800 V (150–1,000 A) provide ample headroom for 575 VAC mains. Convection cooling suffices through 150 A; units at 225 A and above incorporate forced-air cooling. Control signal compatibility spans 4–20 mA (500 Ω input impedance), 0–10 VDC (34 kΩ), and a manual 10 kΩ potentiometer input — connecting directly to PLC analog outputs, temperature controller retransmission signals, or simple manual dials without signal conditioning.