Size the control transformer for your panel from the total sealed VA and the largest inrush.
Add up the sealed VA of every contactor coil, relay, pilot light, and PLC supply on the control circuit. Enter the single largest inrush VA from the device with the biggest momentary draw.
A control transformer steps your line voltage down to a safe control voltage (often 120 V or 24 V) for contactor coils, relays, PLC power supplies, and pilot devices. Size it from two numbers: the total sealed (holding) VA of everything on the circuit, and the largest single inrush VA.
Pick a standard size that covers the continuous sealed load with margin, then confirm the transformer can handle the momentary inrush without dipping voltage enough to drop out other coils. Our control transformer sizing guide walks through a full worked example, and the control panel design guide covers where it fits in the panel.
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