SQL50A — 50A 1200V Three-Phase Bridge Rectifier

The SQL50A is a three-phase full-wave bridge rectifier module that integrates six rectifier diodes into a single metal-cased package. It converts three-phase AC into smooth, low-ripple DC — far cleaner than single-phase rectification — making it the standard front-end for generators, wind turbines, servo/motor drives, and heavy battery-charging systems. Rated at 50A DC output current and 1200V peak reverse voltage, it's designed for continuous industrial loads. The rugged square housing has an (typically isolated) metal baseplate with two mounting holes for direct heatsink bolting, and five terminals: three AC inputs (marked with ~ symbols, sometimes R/S/T) and two DC outputs (+ and −). The quick-connect / screw terminals make it easy to wire into a chassis or busbar.

Electrical & Mechanical Specifications

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Parameter Symbol Value Unit

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Configuration — 3-phase, 6-diode

Max Recurrent Peak Reverse Voltage VRRM 1200 V

Max DC Blocking Voltage VDC 1200 V

Max RMS Input Voltage (line-to-line) VRMS ~840 V

Average Output (DC) Current IO 50 A

(Tc held ~100°C, w/ adequate heatsink)

Peak Forward Surge Current IFSM 400 A

(8.3 ms single half-sine, per element)

Max Forward Voltage Drop (per diode) VF ~1.05 V

(at rated current)

Max Reverse Leakage @ VDC, Tj=25°C IR 10 µA

Operating Junction Temperature TJ -40…+150 °C

Storage Temperature Range TSTG -40…+150 °C

Isolation Voltage (isolated baseplate) VISO ~2500 VAC

Mounting 2× M5 screw through holes

Terminals 5× 6.3 mm faston / screw

Package SQL (metal, square)

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Note: values are typical for the SQL50A class across common suppliers (SEP, Yangzhou, MIC, generic import). Surge (IFSM), I²t, thermal resistance, and whether the baseplate is truly isolated vary by brand — verify against the exact datasheet for the stock you carry.

Typical Applications

• Three-phase power supply and industrial rectification

• Wind turbine and permanent-magnet generator AC-to-DC output

• DC motor drives, servo drives, and CNC spindle power

• Three-phase battery chargers and DC power systems

• Welding equipment and electroplating rectifiers

• UPS, inverter, and frequency-converter DC bus supply

Safety & Usage Cautions

• Always use a heatsink. The 50A rating assumes the case is held cool (≈100°C) with proper heatsinking and thermal paste. Free-air, the usable current is a small fraction of 50A.

• Wire the phases correctly — the three ~ terminals accept the three AC lines; + and − deliver DC. Confirm the top-face marking before connecting, as pinout position varies by brand.

• Do not exceed 1200V peak reverse voltage. Add MOVs / snubbers where the three-phase supply can spike.

• Provide inrush protection (NTC thermistor, pre-charge resistor, or soft-start) when charging large DC-bus capacitors to stay within the 400A surge limit.

• Do not assume the baseplate is isolated unless the datasheet confirms it — verify before bolting to a grounded chassis.

• Derate output current at high ambient temperature and keep junction temperature below 150°C.