Working Principle of the Intermediate Relay

AC and DC Intermediate Relays — Principle, Usage, and Applications

An intermediate relay is an electrical switching device widely used in control circuits.
Its main purpose is to use a low-current control signal to switch or control higher-power electrical equipment.
In simple terms, it converts a small control signal into a larger switching capability to drive loads.

According to the power supply type, relays are divided into AC relays and DC relays, each having its own characteristics and applications.

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1. Working Principle

The operation of an intermediate relay is based on electromagnetic induction.

When current flows through the relay coil, a magnetic field is generated in the iron core.
This magnetic force pulls or releases the armature, causing the contacts to open or close, thereby controlling the load circuit.

Coil Section

The relay contains an electromagnetic coil.
When the coil is energized, it produces a magnetic field that moves the iron armature.

Contact Section

The contacts change state when the coil is energized:

• Normally Open (NO) contacts close
• Normally Closed (NC) contacts open
  
  

This switching action allows the relay to connect or disconnect the controlled circuit.

(Typical terminals: coil A1–A2, contact 13–14 = normally open contact)