Your present location:home >> Technical >> Technical >> How to choose and use the SSR?

How to choose and use the SSR?


How to choose and use the SSR?


1)Correct wiring, don't mistake the input and output circuits and prohibit polarity reversal.
2)Testing the load resistance in order to avoid the short circuit before the power supply turn on.
3)When using the SSR, make sure good heat dissipation of solid-state relay housing and baseplane.
4)Fastening the wires, otherwise, heat generated from the terminal may cause the SSR damage.
5)Solid-state relay presence output leakage current. When do replacing or wiring work,be sure to cut off power to ensure personal safety.
6)Load voltage and current must not exceed the limits prescribed in relay instructions, otherwise it will lead to product failure.
7)Prevent fall and collision before and after installation. Vibration and shock exceed the specified value may damage the relay.
8)For PCB mounting, welding at temperature (240 ~ 260)OC must be completed within 10s.

2.Correct Choosing
2.1 It's important to choose the suitable SSR. The different loads bring surge current or overvoltage when the power turns on. The most common SSR failure is caused by high surge current, thus require redundant design. Suggested SSR block voltage is 2 to 3 times higher than the Load voltage. Refer to following chart for current value.

Table 1: The Inrush current that different load switches

3.Correct Usage
3.1 Input Circuit
3.1.1 SSR shall be energized with adequate power (voltage or current). Min.input voltage (current) must be greater than specified minimum trigger voltage(current) and should not exceed the specified max input voltage (current). Excessive input voltage (current) will cause permanent damage to the relay;2.2 Please refer to SSR specification before using them, make sure that the use environment meet the requirements.

3.1.2 Input side transient pulse may result in malfunction of the relay, short connection and add filter circuit 
can effectively prevent malfunction of the relay;
3.1.3 For DC input, be careful about the correct polarity wires. Over reverse polarity voltage may cause permanent damage to 
the relay.
3.2 Output Circuit
3.2.1 AC load
Switching the AC inductive load may bring over voltage, it may be larger than the SSR voltage value and damage the product, as built-in RC snubber circuit inhibitory capacity is limited. Parallel connection between MOV (metal oxygen varistor) and the SSR output terminals is recommended. Suggesting the MOV type: 

3.2.2 DC load
Switching load such as the coil load, electromagnetic valve may bring over voltage, parallel connection between the diode and the load terminals is recommended. Otherwise, over transient voltage will damage SSR output devices. Reverse protection diode have the best transient voltage suppression result. But coil and electromagnetic valve reset time becomes longer, please confirm actual loop before use. In addition, to reduce the reset time, you can use diodes and Zener diode. Then, the higher stablized voltage of Zener diode, the shorter reset time.


3.3 Environment
Please refer to the curve of "Max. Load Current vs. Ambient Temperature" for thermal design, to avoid SSR failure caused by high temperature. Multiple SSR installed side by side may occur SSR local abnormal heat, so sufficient space to prevent heat accumulation is needed. As the space dimensions, refer to the detailed product specifications. (If not specified, it is recommended to take a thickness of SSR as the distance).
For the SSR rated current 5A or less, generally do not need external heat sink; for rated current more than 5A, external heat sink is a must. Between the heat sink and the relay base, thermal grease should be evenly applied.
Do not operate or store the Relay in locations subject to direct sunlight or ultraviolet rays, otherwise the resin will be deteriorated which consequently leads to cracks and other damages to the case.
Do not operate or store the relay in locations subject to exposure to water or chemicals; otherwise rust,corrosion and deterioration of the resin will occur. For SSR long-term storage, the terminal surface exposed to the air cause oxidation and the terminal weldability and conductivity will be reduced. Therefore, before use the long-term storaged SSR, we must first check the terminals weldability and conductivity. Only qualified products can be used.

3.4 Mounting

3.4.1 PCB SSR
Terminal hole size and pan diameter, diameter of through-hole pan can be a little smaller than the values in the table .

3.4.2 Panel-mounting SSR
Reference the torque

TypeInfo: Technical

Keywords for the information:SSR ssr relay AC ac SSr relay 


Ad:No.130,Guankouzhong Road,

Jimei Dist,361023 Xiamen Fujian,China

Hotline:0592-7268263 6387007-8069

Copyright page:Xiamen Jinxinrong Electronics Co., Ltd