Type Selection And Working Principle Diagram Of Power-Off Delay Relay

Update time:Nov 24 , 2023 Views:85

The power-off delay relay is that when the coil of the time relay is energized, each delay contact acts instantaneously. After the coil is powered off, the contact is in the delayed set working state. When the set delay reaches, the delay contact returns to the initial state. To control a motor, it is required to restart the motor after pressing the stop button for a period of time. In this case, the power-off delay relay is required to achieve the above functions. There are too many time-delay relay manufacturers and models in China. How do you look at whether a relay is a power-off delay relay or a power-on delay relay when you buy and use and read the circuit drawings? Next, I will introduce a relay selection method and its working principle.


The contact of the power-off delay time relay acts after the relay is powered on. After the relay is powered off, the delay time reaches the preset time and the contact returns to the original state. Power on delay time is the contact of the relay. After the relay is powered on, the contact will act when the delay time reaches the set time. After the relay is de energized, the contact returns to the original state.


How to see whether a relay is a power-off delay relay or a power on delay relay? Let's introduce a kind of electrical symbol printed on the relay case to distinguish it. How to identify the time in the circuit diagram or the physical diagram mainly depends on the drawing of the circular arc in the graphic symbols. Let's take a look at the graphical symbols of the contacts of the power on delay time relay:

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The contact of the power on delay time relay looks at the arc, and the arc moves toward the center of the circle, driving the contact to delay action. Look again at the graphical symbols of the contacts of the power-off delay time relay:

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The contact of the power-off delay time relay also looks at the arc, and the contact acts after energization. After power failure, the arc moves toward the center of the circle, which drives the contact to reset in time delay.

In fact, sometimes relays also have instantaneous action contacts. These contacts have the same functions as common relay contacts. They act on power and restore the original state after power failure. The various models of time delay relays used can be divided into DC (12V 24V 110V, etc.) and AC (24V 36V 110V 220V 380V). Both are made according to the needs of customers. Please be careful when using them. The working voltages of both are ranked. The following is a brief introduction to the working principle of the time delay relay composed of separate electronic components.

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It uses a miniature transformer to step down the voltage. The primary input power supply is AC 220 V, and the secondary has two groups of power supplies ac18 V and AC12 v. ac18v passes through a bridge rectifier diode (1N4001 × 4) After C1 (30uf / 32V) filtering, it provides DC working power for KA miniature relay and composite triode VT1 and VT2 (9012). Another group of AC 12V power is supplied to RP1 transformer through VD1 half wave rectification, C2 electrolytic capacitor filtering, and C3 is a single stone capacitor. It has good working characteristics and can be used in delay charging and discharging circuits. There are KA normally open and a group of KA normally closed contacts of jz01-33 relay in the diagram. Their main role in the circuit is as mentioned above. After the preset time is completed, the relay will return to the initial state to prepare for the next step.


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