120A 3-32V DC to AC solid state relay (SSR) features high structural strength, good impact resistance, and strong shock resistance. The SSR offers a reliable switching the commercial and industrial loads, such as computer peripheral interface device, printing machine, molding machine, food machine, packaging machine, and so on.
- Built in RC absorption
- Photoelectric isolation
- SCR output
- LED indicator for operation status
- Removable protective cover for safety
- Panel mount
- Zero-crossing switch type
||Control voltage range
|Max. input current
|Must operate voltage
|Must release voltage
||Load voltage range
|Maximum off-state leakage current
|Maximum off-state time
|Maximum on-state voltage drop
||Dimension L – W – H (mm)
|Dielectric strength (input to output)
|Dielectric strength (input, output to the base)
* When the load current is higher than 10A, a heat sink must be installed to the solid state relay, or the SSR relay should be mounted on a metal base plate with heat dissipation effect, and the thermal grease is applied between them.
* When the load current is 40A or more, a fan cooling radiator or water cooling radiator must be equipped.
* Heat sink is Not included.
Dimension (Unit: mm)
Tips: Construction of solid state relays
Solid-state relays consist of three parts: the input circuit, isolation (coupling) and the output circuit.
- Input circuit
According to different types of input voltage, the input circuit can be divided into DC input circuit, AC input circuit and AC-DC input circuit. Some input control circuits also have TTL / CMOS compatible, positive and negative logic control and anti-phase functions, etc. and can be easily connected with the TTL, MOS logic circuit. For the control signal with fixed control voltage, a resistive input circuit is used. The control current is guaranteed at 5mA or higher. For control signals with a large range of voltage (such as 3 ~ 32V), use a constant current circuit to ensure that the current works reliably at 5mA or higher over the entire voltage range.
- Isolation and coupling
The way of isolation and coupling of solid state relays’ input and output circuit includes photo coupling and transformer coupling. Photo coupling usually uses the photodiode - phototransistor, photodiode - bidirectional light activated SCR, photovoltaic cells, to achieve isolation control of the control side and the load side; high-frequency transformer coupling is to use the self-excited high frequency signal generated by input control signal to form a drive signal through coupling to the secondary, rectification, and logic circuit process.
- Output circuit
The power switch of SSR is directly connected to the power supply and load terminal to switch on and off the load power supply and mainly uses high power transistors (switch tube-Transistor), unidirectional SCRs (Thyristor or SCR), bilateral SCR (triac), metal-oxide -semiconductor field effect transistor (MOSFET), insulated gate bipolar transistor (IGBT). Solid state relays’ output circuits can also be divided into DC output circuit, AC output circuit and AC-DC output circuit and other forms. According to the load type, it can be divided into DC solid state relay and AC solid state relay. Bipolar devices or MOSFETs can be used for DC output and two SCRs or a triac for AC output. AC solid state relays can be divided into single-phase AC solid state relays and three-phase AC solid state relays. AC solid state relays, according to the timing of turn-on and turn-off, can be divided into random AC solid state relays and zero-crossing AC solid state relays.