Description

The 5STP18H4200​ is a high-power Phase Control Thyristor (PCT) from ABB’s 5STP series, manufactured by ABB Switzerland Ltd (Semiconductors division, now under Hitachi Energy). Rated at 4200 V repetitive off-state/reverse blocking (V_DRM/V_RRM) and 2075 A average on-state current at T_c=70 °C, it is engineered as the primary controlled switching element in series valve strings for HVDC converters, SVC/TCR static VAR compensators, large traction rectifiers, and industrial heating / melting applications where thousands of amperes must be phase-controlled with μs-precision.

Application Scenarios

A Nordic steel service center runs a 90 MVA electric arc furnace (EAF) that was hammering the regional grid with 6–8 % voltage flicker during scrap melt-in. The utility threatened a penalty tariff unless flicker dropped below 3 %. The plant’s SVC used a TCR leg with twelve 5STP18H4200​ devices in series per phase (4200 V × 12 ≈ 50 kV DC blocking margin on a 33 kV system). After 16 years of two-shift melting, one phase started misfiring intermittently — the gate driver logged “late turn-on” on valve position 7 during high di/dt transients. The integrator pulled the suspect 5STP18H4200, curve-traced it, and found V_TO had drifted from 0.96 V to ~1.18 V and the latching current I_L had crept up — classic signs of free-floating silicon wear after ~120 k thermal cycles. Swapping all twelve pieces in that phase (valve strings are wear-matched; mixing old+new drifts the dynamic voltage sharing) restored clean phase-angle control; flicker dropped to 2.4 % inside the same shift. What the maintenance lead noted afterward: the 5STP18H4200​ is press-pack, so the swap was unbolt the water-cooled heatsink clamps, lift the 0.9 kg disc, drop the new one, re-torque to 50 kN ±10 %, and bleed the cooling loop — no solder, no bonded leads, no “rework the busbar.” For an EAF where one unplanned SVC down = meltdown hold + utility penalty, the valve refresh paid for itself before the next heat.

Parameter

Technical Principles and Innovative Values

• Innovation Point 1: Free-floating silicon wafer in press-pack.​ The 5STP18H4200​ uses ABB’s patented free-floating silicon — the wafer isn’t rigidly bonded to the Mo disc, it “floats” under clamping pressure. This decouples thermal-expansion mismatch between Si (2.6 ppm/K) and Mo/Cu (5–6 ppm/K), so after 100 k+ power cycles the wafer doesn’t crack. That’s why EAF TCR valves (where each heat is a thermal cycle) routinely see 15–20 year life on 5STP18H4200​ whereas soldered dice fail in 6–8.
• Innovation Point 2: Double-side power + signal in one disc.​ The 5STP18H4200​ carries the main anode/cathode on the two flat faces (double-side cooled, water or forced-air) and the gate + auxiliary cathode on removable Faston / ETFE pigtails (gate white, aux-cathode red, 0.5 mm²). No separate gate board to mount — the valve designer lands the gate driver on a mezzanine above the disc stack and plugs in. dV/dt_crit hits 1000 V/μs under rated recovery, so snubber design stays sane even in TCR’s dirty switching environment.
• Innovation Point 3: Low V_TO + low r_T combo.​ At 0.96 V threshold and 0.285 mΩ slope, the 5STP18H4200​ dissipates ~3.1 kW at 2000 A continuous — compare that to older GTO-like thyristors pushing 4.5–5 kW at the same current. Over a 12-pulse TCR with 36 discs, that’s ~60 kW saved in the valve hall, which translates to smaller chillers and less ΔT stress on the wafers. Positive feedback loop on reliability.

Application Cases and Industry Value

Case 1 — Traction rectifier substation (Switzerland, 2019):​ 15 MVA 50 Hz → 16.7 Hz converter for railway supply, 12-pulse bridge using 5STP18H4200​ in each arm. After 18 years, one arm started showing uneven current sharing across the series string — clamping force audit revealed three discs had relaxed to 42 kN (below the 45 kN min) because the stainless Belleville washers had settled. Rather than re-torquing live (risk of fracturing a 20-year-old ceramic), the maintainer swapped all six discs in that arm with fresh 5STP18H4200, re-torqued to 50 kN with new washers. String balance returned to <3 % deviation; the substation avoided a full bridge retrofit quoted at CHF 210 k.Case 2 — Aluminum smelter potline rectifier (Middle East, 2023):​ Two 80 kA diode + thyristor hybrid rectifiers, phase-control done by 5STP18H4200​ strings on the AC side for tap-less voltage trim. Ambient regularly hits 52 °C in the summer; the original design used forced-air on the disc heatsinks, but sand ingestion was raising R_th(c-h). The plant migrated to closed-loop water cooling on the same 5STP18H4200​ clamps (press-pack is media-agnostic) — T_vj dropped 18 °C at full load, and V_T drift slowed enough that they extended the recalibration interval from 6 months to 14 months. One potline → 24 rectifiers, the water-cooling retrofit paid back in 11 months on reduced scrap pot re-heats.