Working Principle and Structure of Time Relay

 Working Principle and Structure of Time Relay A time relay is a relay with a delay function that can act after a certain delay upon receiving a signal.
1. Core Components
A time relay mainly consists of the following parts:
(1) Electromagnetic system: generates a magnetic field to attract the iron core.
(2) Timing mechanism: realizes the delay function, commonly including pneumatic and electronic types.
(3) Contact system: includes both delayed contacts and instantaneous contacts.
2. Working Process
Time relays can be divided into energized-on delay type and de-energized-on delay type based on the delay mode:
(1) Energized-on delay process:
• When the coil is energized, the electromagnetic system generates magnetic force.
• The iron core in the timing mechanism is attracted, and the timing mechanism starts counting.
• When the preset delay time is reached, the timing mechanism releases the iron core.
• The contact system operates.
(2) De-energized-on delay process:
• When the coil is energized, the electromagnetic system generates magnetic force, and the contact system operates immediately.
• When the coil is de-energized, the timing mechanism starts counting.
• When the preset delay time is reached, the timing mechanism releases the iron core.
• The contact system resets.
3. Equivalent Circuit Model
The equivalent circuit model of a time relay mainly considers the coil and contact parts:
(1) Coil part: equivalent to a series circuit of inductance and resistance, with characteristic parameters including coil resistance, inductance, and rated voltage.
(2) Contact part: includes delayed contacts and instantaneous contacts, equivalent to a time-controlled switch.