Time Relay

Introduction

The time relay is a kind of relay that needs to pass the specified precise time to generate a jump change (or contact action) when the input action signal is added (or removed). It is an electrical component used in circuits that use lower voltages or smaller currents to turn on or off higher voltage, higher current circuits. At the same time, the time relay is also a control device that realizes delay control by using electromagnetic principle or mechanical principle.

classification

The time relay can be divided into two types: power-on delay type and power-off delay type.

There are many types of time relays, such as air damping type, electric type and electronic type.

The air damping type time relay has a large delay range (0.4 to 60 s and 0.4 to 180 s), and has a simple structure but low accuracy.

principle

When the coil is energized, the armature and the pallet are attracted by the core and instantaneously moved down, causing the momentary action contact to be turned on or off. However, the piston rod and the lever cannot fall together with the armature because the upper end of the piston rod is connected to the rubber film in the air chamber. When the piston rod starts to move downward under the action of the release spring, the rubber film is then concave downward. The air in the air chamber becomes thin and the piston rod is dampened and slowly descends. After a certain period of time, the piston rod is lowered to a certain position, and the delay contact is actuated by the lever, so that the breaking contact is opened and the moving contact is closed. From the energization of the coil to the completion of the delay contact, this time is the delay time of the relay. The length of the delay time can be changed by adjusting the size of the air inlet of the air chamber with a screw.

After the attracting coil is de-energized, the relay is restored by the action of the return spring. Air is quickly expelled through the vent.

Features

As an execution device in the simple program control, when it receives the start signal, it starts timing, and after the timing is finished, its working contacts are opened or closed, thereby promoting the subsequent circuit operation. In general, the time delay performance of the time relay is adjustable within the design range, making it easy to adjust its delay time. It is impossible to start the delay closure with a single time relay. After closing for a period of time, it will be disconnected again. After the delay is closed, the delay will be disconnected, but in general, a certain number of time relays and intermediate relays are configured. It can all be done.