Definitions for AC-3, contactor, DOL, PLC, VFD, and more. Each term links to relevant products.
IEC contactor duty for squirrel-cage motor switching. Rated for direct-on-line start and run.
Electromechanical switch for high-power loads. Used for motor control, lighting, heating. Rated by operational current (AC-3) and coil voltage.
Direct-On-Line. Motor starting method where full voltage is applied at start. Simple and inexpensive; high inrush current.
Ingress Protection. IEC 60529. First digit: solid particles (0–6). Second digit: liquids (0–9). IP54 = dust-protected, splash-proof.
Sinking output. Output goes to 0V when active. Common in Asian sensors. Use with sourcing inputs.
Protects motor from overcurrent. Thermal or electronic. Trips on sustained overload; allows brief inrush. Must be sized to motor FLC.
Programmable Logic Controller. Industrial computer for automation. Scans inputs, executes ladder logic, updates outputs. Deterministic scan cycle.
Sourcing output. Output goes to +24V when active. Common in European sensors and PLCs. Use with sinking inputs.
Reduces motor inrush current by ramping voltage. Limits mechanical stress. Alternative to star-delta for pumps and conveyors.
Reduced-voltage motor starting. Start in star (reduced torque), switch to delta for run. Requires 6 motor leads and 3 contactors.
Variable Frequency Drive. AC motor speed control by varying frequency. Energy savings, soft start, precise speed. Requires screened motor cables.
