When to use: Use this when selecting a control (machine-tool) transformer that powers a control circuit of relays, contactors, PLC supplies, pilot lights, and solenoid valves. A control transformer must carry the continuous sealed VA of everything held energized, and simultaneously supply the inrush VA of the largest device that picks up — without the secondary voltage dipping so far that other coils drop out. Size it for both the sealed load and the inrush voltage dip.