25 A RMS, 600 V — the load capacity and mains-voltage fit
The STMicroelectronics BTA24-600BWRG is a Snubberless™ Alternistor triac rated for 25 A RMS on-state current and 600 V off-state voltage, housed in a TO-220-3 through-hole package. It is designed for AC switching applications where inductive loads — motors, solenoids, transformers — would otherwise require an external RC snubber network.
The Snubberless™ designation means this triac uses a special gate structure that prevents false turn-on from high dv/dt transients, eliminating the need for a snubber circuit across the main terminals. The Alternistor construction (also called a hi-com triac) blocks turn-on in quadrant IV, which is the typical failure mode when driving inductive loads without a snubber. This makes the BTA24-600BWRG a drop-in for designs that previously used a standard triac plus snubber, provided the gate trigger current of 50 mA max and gate trigger voltage of 1.3 V max are compatible with the existing driver.
Surge current and thermal margin for motor starts
Non-repetitive surge current is rated at 250 A for 50 Hz and 260 A for 60 Hz (one cycle). This is the rating that determines whether the triac survives the inrush from a motor start or a capacitor bank charging. For a 25 A continuous load, a 250 A surge capability provides roughly a 10× margin — adequate for most direct-on-line motor starts, but if the load is a large transformer or a bank of electrolytics, the surge current should be calculated against the actual inrush envelope. The hold current (Ih) is 75 mA max. If the load current drops below this threshold during the zero-crossing region, the triac will commutate off prematurely. For resistive loads this is rarely an issue, but for low-current inductive loads — a small fan or a relay coil — verify that the load current exceeds 75 mA at all points in the cycle to avoid half-wave operation.
Temperature range and mounting for industrial environments
The TO-220-3 package has a metal tab that must be heatsinked for continuous 25 A operation — the tab is electrically connected to the MT2 terminal, so an insulating pad and thermal grease are required if the heatsink is grounded. The through-hole mounting (TO-220-3) is a standard power package. It is compatible with wave-solder processes and can be hand-soldered for rework.