SSJ-21A type static time relayDetailed product description：

1、 Overview

1. Main purpose of the product
The SSJ series static time relay (hereinafter referred to as the relay) is used in the secondary circuit relay protection and automatic control circuit of the power system as a delay device to enable the controlled components to obtain the required delay. This relay is an integrated circuit static relay with high precision, low power consumption, accurate action time, intuitive and convenient setting, and wide range. The working power supply adopts switch power conversion and is universal for AC and DC, completely replacing electromagnetic time relays.

2、 Classification and Meaning of SSJ-21A Static Time Relay Models



Comparison table between this relay model and the replaced old model:



3、 Product composition and working principle

1. This relay has a much higher delay accuracy than the DS type electromagnetic time relay, which can meet the requirements of shortening the protection time difference in power system relay protection. It is currently an ideal replacement product for time relays. The external structure, internal wiring, working mode, and setting range of this relay are the same as those of the DS series time relay, except for the setting mode. The setting time is calculated by multiplying the three digits of the dip switch by the 0.01s or 0.1s time base. Changing the setting value does not require verification.  
2. This relay is an action delay digital time relay composed of imported CMOS integrated circuits. The relay consists of an oscillator, a frequency divider, and a three-stage pulse counter, and the delay value is set through a BCD code dip switch.  
3. Relays are usually not charged. After the rated voltage is applied, the internal instantaneous relay of the relay acts and the crystal oscillator starts oscillating, generating clock pulses that are divided by frequency
Afterwards, the counter counts the number of pulses. When the counted number of pulses reaches the delay setting value, the trigger flips and drives the output relay to operate, achieving the required delay. Due to the use of a crystal oscillator and the addition of a time compensation preset circuit, it strictly conforms to the setting value for extremely short delay values and has extremely high accuracy.   
4. The double delay loop of the relay has relatively independent delay and drives one executing relay separately. Therefore, the dynamic closing contacts of the two executing relays can be used as the stopping and sliding contacts of the relay according to the length of the delay. However, after the sliding contact is closed, its closed state remains until the relay loses power and returns. If the user needs the sliding contact to close for a certain period of time and return immediately, they need to specify it when ordering and provide the duration of the sliding contact's closure.
5. The schematic diagram of the relay is shown in Figure 1.   



4、 Technical requirements

1. The rated values and specifications are shown in the table above.  
2. Delay accuracy
a、 The average error of the delay setting value: Under reference conditions, the absolute value of the average error of the relay delay setting value is not greater than 0.1%+3ms of the setting value; the average error=(average of 5 measurements - setting value)/setting value × 100%.   
b、 Delay consistency: Under benchmark conditions, the delay consistency of the relay is not greater than the set value (3-10ms).  
c、 At temperatures ranging from -10 to 50 ℃, the absolute value of the average error (including consistency) of any delay setting value shall not exceed 0.1%+5ms of the setting value
3. Working voltage: When the operating voltage is not greater than 70% of the rated voltage, the relay should work reliably.  
4. Return time of relay
The time for the outlet contact to return to the starting position after cutting off the electrical power supply should not exceed 25ms for varieties that use DC power supply
5. When the return voltage of the relay decreases by no less than 10% of the rated voltage, the relay contacts should reliably return.
6. Power consumption
DC48V， Not exceeding 2W
DC110V or AC100-127V, not exceeding 4.5W (6.5VA)
DC or AC220V, not exceeding 8.1W (13VA).
7. Thermal performance requirements
This series of relays can operate for a long time when powered on, and can withstand 1.1 times the rated voltage value for a long time when the ambient temperature is 50 ℃.
8. Power supply working characteristics: The power supply can slowly rise and fall, suddenly turn on/off, or supply power through shaking contacts. The relay can work normally and there is no zero second outlet or instantaneous outlet phenomenon.   

5、 Internal wiring of SSJ-21A static time relay (front view)



6、 Appearance and opening size

SSJ-10 adopts a protruding fixed structure, and the appearance and installation hole size are detailed in Figure 1



The SSJ-20 adopts a protruding plug-in structure, and the appearance and installation hole size are detailed in Figure 2



SSJ-30 adopts an embedded insertion structure, and the appearance and installation hole size are detailed in Figure 3



SSJ-40 adopts a protruding guide rail structure, and the appearance and installation hole size are detailed in Figure 14