Pamalihon sa mga Relay sa mga Sistema sa Signal

Unsa ang Relay?

Ang relay usa ka electrical switch nga gigamit og electromagnetic force aron kontrolhon ang pagbukas ug pagtupok sa usa o daghan pa nga electrical circuits. Kasagaran naka-angkla kini sa core components sama sa electromagnet, contacts, ug springs. Bisan unsa nga energized ang coil sa electromagnet, giproduce niini ang magnetic field nga moadto o mobo ang armature, sukad na nag-drive sa contacts aron maactuate ug mahimo ang circuit connection o disconnection.

Klasipikasyon sa Relays

Primero gi-divide ang relays ngadto sa duha ka major categories: DC Relays ug AC Relays.

• DC Relays:

  • Power Supply: Powered by a DC source.
  • Classification: Based on the polarity of the current, they can be categorized as Non-polarized Relays, Polarized Relays, and Biased Relays.
  • Principle: All are electromagnetic relays that operate by using the magnetic field generated from the energized coil to attract an armature, which in turn drives the contact system to actuate.

• AC Relays:

  • Power Supply: Powered by an AC source.
  • Classification: Based on the operating principle, they include both Electromagnetic Relays and Induction Relays.
    • Electromagnetic Relay: Operates similarly to a DC electromagnetic relay, but its core usually incorporates a shading coil or shading ring to prevent vibration of the armature caused by the zero-crossing of the AC current.
    • Induction Relay: Uses the interaction between an alternating magnetic field generated by the coil and eddy currents induced in a movable part (such as a vane) by another alternating magnetic field to produce an electromagnetic force that drives the vane to rotate and actuate the relay.

Application of Relays in Railway Signaling Systems

Widely used ang relays sa railway signaling systems. Main types include: DC non-polarized relays, polarized relays, polarized holding relays, AC relays, etc.

• DC Non-polarized Relay:

  • A DC electromagnetic relay whose coil has no polarity distinction and can be connected to a DC power source of any polarity, reliably actuating upon energization.

• Polarized Relay:

  • A DC polarized relay with a fixed positive and negative polarity for its coil, requiring connection to a DC power source of specified polarity.
  • When forward current flows through the coil, the front contact closes with the common contact; when reverse current flows, the back contact closes with the common contact; when the coil is de-energized, the relay does not actuate.

• Polarized Holding Relay:

  • A special type of polarized relay possessing both polarity and holding functions.
  • When energized, it closes the corresponding contacts based on the polarity of the coil current; after de-energization, the contacts remain in their previous state until current of the opposite polarity is applied. This "memory" characteristic makes it widely used in logic circuits.

• AC Relays:

  • Powered by AC, including various types such as signal lamp filament transfer relays, FD-type electric coders, JRJC-type two-element two-position relays, and rectifier relays.

• Rectifier Relay:

  • An improved version based on a DC non-polarized relay. It incorporates a rectifier and voltage stabilizer at its input, converting AC to DC before supplying it to the relay coil.
  • The DJ (Filament Relay) used in signal lamps typically employs this type of relay.

• Two-element Two-position Relay:

  • A typical induction relay. It uses the interaction of eddy currents induced in a vane by two alternating magnetic fields (usually from track power and local power) to generate an electromagnetic force that drives the vane to rotate, thereby actuating the relay.
  • The GJ (Track Relay) in a 25Hz phase-sensitive track circuit is this type of relay.

• Time Relay:

  • A relay with a time-delay function. When an input signal is applied or removed, its output contacts close or open only after a preset delay time.
  • Time relays are commonly used in turnout starting circuits to achieve time control during turnout conversion.

Rason sa Paggamit sa Relays sa Railway Signaling Systems

• High Reliability:Isip usa ka mature switching component, ang relays adunay simple structure, stable performance, ug makapuyo og dili molabay sa harsh railway environments (such as temperature variations, vibration, moisture, and dust). Kritikal kini aron asegurado ang safe operation sa key equipment sama sa signals, turnouts, ug track circuits.
• High Safety:Ang "Fail-Safe" design principle sa relays fundamental sa ilang application sa railway signaling. Kon magfail ang relay (e.g., coil break, power loss), ang iyang contacts automatic open pinaagi sa gravity o spring force, causing the signaling system to enter the safest state (e.g., a signal showing red), thereby minimizing the risk of accidents.
• High Precision and Determinism:Ang relays adunay short ug predictable response times, enabling precise switching control. Sa complex interlocking logic, highly deterministic ang relay operations, ensuring the accuracy of signal control.
• Flexibility and Scalability:Ang relay logic circuits (relay interlocking) makapahimo og complex control logic pinaagi sa different wiring methods. Easy to design, modify, ug expand ang sistema basehan sa station layout ug operational requirements.
• Good Electrical Isolation:Ang control circuit (coil side) ug ang controlled circuit (contact side) sa relay completely electrically isolated, enhancing the system's immunity to interference ug safety.