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Examoogle • User • info@examoogle.com • EE-2024-8821
Chapter 1 of 12 • Page 1 of 248🔒 Protected PDF • Watermarked
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Types of Output of PLC are____.
Relay
Triac
Transistor
All
All
Quick Summary: Programmable Logic Controllers (PLCs) utilize different output modules to interface with various field devices, categorized primarily by their switching mechanism and electrical characteristics. Relay, Triac, and Transistor modules represent the three standard industrial output types used to control AC/DC loads.
Programmable Logic Controllers (PLCs) utilize different output modules to interface with various field devices, categorized primarily by their switching mechanism and electrical characteristics. Relay, Triac, and Transistor modules represent the three standard industrial output types used to control AC/DC loads.
fswitch∝Tdelay1 — Switching frequency constraint relative to propagation delay
Ploss=I2⋅Ron — Power dissipation in solid-state (Transistor) outputs
Relay outputs are versatile for both AC/DC but suffer from mechanical wear.
Triac modules are strictly for AC loads and provide high reliability due to no moving parts.
Transistor outputs (NPN/PNP) are high-speed and ideal for DC pulse train applications.
Selection depends on load voltage, current requirements, and frequency of operation.
Relay: Isolation and high voltage compatibility.
Transistor: Extremely high switching speeds.
Triac: Silent operation and no contact bounce.
Relay: Low switching frequency.
Triac: High leakage current in OFF state.
Transistor: Limited to low DC voltages.
Relay: Heavy duty contactors and solenoids.
Triac: AC valves and heaters.
Transistor: Stepper motor drivers and logic sensing.
| Feature | Relay | Triac |
|---|---|---|
Load Compatibility | AC and DC | AC Only |
Switching Speed | Slow (10-20ms) | Very Fast (μs) |
Relay life cycles are typically limited to 10°5 to 10°6 operations.
Transistor modules are often categorized as 'sinking' (NPN) or 'sourcing' (PNP).
D is correct — Relays, Triacs, and Transistors are all standard semiconductor/mechanical switching technologies used in PLC output cards.
When selecting an output module in an exam context, check if the load is AC or DC first; DC-only loads often favor Transistors for speed, while AC loads often require Triacs or Relays.