1. Main purpose:
Heat treatment (electric furnace plant, electric heating) chemical fiber equipment, textile machinery equipment, tempered glass equipment, plastic extruder, injection molding machine, fountain control
2. Selection method of solid state relay:
(1) Resistive load
Single phase: load (KW)/voltage (V) = current (A) * (1.5 or 2 times) = the nominal current of the solid state relay;
Three-phase: load (KW)/[voltage (V)*3] = current (A)* (1.5 or 2 times) = the nominal current of the solid state relay;
(2) Inductive load
Single phase: load (KW)/voltage (V) = current (A) * (5 or 7 times) = the nominal current of the solid state relay;
Three-phase: Load (KW)/[Voltage (V)*3] = Current (A)* (5 or 7 times) = the nominal current of the solid state relay;
(3) Capacitive load
Single phase: load (KW)/voltage (V) = current (A) * (10 times) = the nominal current of the solid state relay;
Three-phase: Load (KW)/[Voltage (V)*3] = Current (A) * (10 times) = the nominal current of the solid state relay;
3. Over-current and over-voltage protection measures. Over-current and load short-circuit are the main causes of permanent damage to the SSR. The selection of fast fuses and air switches is one of the over-current protection methods. For small-capacity SSRs, magnetics can also be used. fuse. In addition to the RC absorption circuit inside the SSR, the overvoltage protection can also use a parallel metal oxide varistor (MOV). The size of the MOV area determines the absorption power, and the thickness of the MOV determines the protection voltage value. Generally 220V series SSR can choose 430V-600V varistor, 380V series SSR can choose 750V-900V varistor.
4. Heat and heat dissipation of SSR: The maximum heat of SSR when it is turned on is calculated according to the actual working current *1.2W/A. In the heat dissipation design, the ambient temperature, ventilation conditions (natural cooling, fan cooling) and SSR should be taken into consideration. Factors such as installation density. The 2A, 3A, and 5A series do not need an external radiator. Spiral SSR only needs to be installed on a metal plate with good heat dissipation or a special guide rail bracket for Gute when applied to long-term current below 10A. Above 10A, it needs to be installed on a radiator. When current is greater than 40A, it needs to be cooled by a fan.
5. Constant current: The input current of the single-phase SSR should be controlled between 6mA and 25mA, and the input control current of the three-phase solid state relay should be between 18mA-75mA. The whole series of SAP, SA3 and some varieties of SAI have built-in constant current input circuit, and the voltage input of 3V to 32V does not need to add current limiting resistor. When using SAI, SAQ, SDP series solid state relays, attention should be paid to control the input current within 25mA. When the input voltage is 4-8V, there is no need to connect a current-limiting resistor; when the input voltage is 8-32V, a 1/4W current-limiting resistor should be connected in series, and the resistance is between 0.5K-1.5K.
6. Installation precautions:
a) A radiator is selected according to the current size, overall dimensions and environmental conditions of the selected relay. The radiator can be natural air-cooled, forced air-cooled or water-cooled. Since the solid-state relay is insulated, multiple solid-state relays can be installed on the same radiator.
b) The installation surface of the radiator should be flat and smooth, free of scratches and debris, and its surface finish should be less than 10um.
c) Before installing the solid state relay on the radiator, use fine sandpaper to gently wipe off the oxide layer on the surface of the radiator and clean it with absolute ethanol. Then apply a thin layer of thermally conductive silicone grease (about 0.5um thick on each side) evenly between their contact surfaces to make good contact between them to reduce contact thermal resistance. In order to facilitate the heat dissipation of the solid state relay, it can work in the best condition.
d) When the module is fastened to the surface of the radiator, use M3 and M5 screws and spring washers, and fasten them with a torque of 0.58-0.98N.M and 4-6N.M.