When the receiving part receives an external signal, after a period of delay to make the executive part of the relay, called time relay. 

What are the two categories of time relays?

There are two main categories: Energized time delay and disconnected time delay. 

The electrical principle symbol is represented by KT.

The side of the time relay is usually marked with its corresponding wiring diagram, as shown on the right side of the diagram above. 

(1) 2, 7 Pins
2 and 7 pins are to provide working voltage power supply to the time relay, 7 pins to 24V positive, 2 pins to 0V negative.

(2) 1, 8 Pins
1 and 8 pins are the common terminal of the contact, need to access the type of load voltage driven. 

(3) 1, 3, 4 Pins
1, 3, 4 pins are a set of jump contacts, 1 and 4 pins are normally closed contacts, before the delay is closed. 

1 and 3 pins are normally closed contacts, before the delay is closed. 1 and 3 feet is a normally open contact, before the delay is open, in the set delay time arrived, 1 and 4 feet immediately from the normally closed point into a normally open point, at the same time 1 and 3 points of the normally open point into a normally closed point. 

8, 5, 6 feet is another set of jump contacts of the time relay, 8 and 5 feet is a normally closed point, 8 and 6 feet is a normally open point, its working principle and 1, 3, 4 feet is similar, here No longer repeated.

How does the time relay delay start/disconnect work?

Time delay start: 
Time relay 2, 7 foot coil after the power, assuming that the set delay time is 5 seconds, 5 seconds after the 1-3 contacts and 6-8 contacts closed on, the load delayed 5 seconds to get power operation.

Delayed disconnection:
After the time relay 2 and 7 pin coils get power, the load will run when it gets power. Suppose the set delay time is 5 seconds, after 5 seconds, the 1-4 contacts and 5-8 contacts will be changed from closed to open, and the load will stop without power.

24V DC time relay and 220V AC time relay wiring method is the same, but the coil supply voltage is different, wiring must pay attention to the coil voltage instructions, so as not to burn the time relay.

What are the factors to be considered while selecting a time relay?

The following parameters should be considered when using time relays.

(1) Voltage of the controlled circuit
According to the voltage of the controlled circuit to choose the voltage of the time relay attraction coil. 

When using to check the power supply voltage and frequency and the time relay rated voltage and frequency is consistent. 

According to the product wiring diagram correct wiring, DC power supply time relay, need to pay attention to the coil power supply positive and negative polarity.

(2) Delay accuracy
If the time delay accuracy requirements are high, you can choose transistor type time relay or electric type time relay.

(3) Delay time range
According to the need to choose the time relay delay time range.

(4) Specific time relay
When using non-contact components to control time relays, the output section should be isolated using photo-couplers as far as possible.