Detailed description of thyristor module application
1. Application fields of SCR modules
This smart module is widely used in applications such as temperature control, dimming, excitation, electroplating, electrolysis, charging and discharging, electric welding machines, plasma arcs, inverter power supplies, etc., where power energy needs to be adjusted and transformed, such as industry, communications, and military. Various electrical controls, power supplies, etc. can also be connected to the multi-function control board through the control port of the module to realize functions such as current stabilization, voltage stabilization, soft start, etc., and can realize over current, over voltage, over temperature, and equalization. Protective function.
2. Control method of thyristor module
Through the input module control interface an adjustable voltage or current signal, the output voltage of the module can be smoothly adjusted by adjusting the size of the signal, so as to realize the process of the module output voltage from 0V to any point or all conduction.
Voltage or current signal can be taken from various control instruments, computer D/A output, potentiometer directly divides voltage from DC power supply and other methods; control signal adopts 0～5V, 0～10V, 4～20mA three commonly used methods Control form.
3. Control port and control line of SCR module
The module control terminal interface has three forms: 5-pin, 9-pin and 15-pin, corresponding to 5-pin, 9-pin, and 15-pin control lines respectively. Products that use voltage signals only use the first five-pin port, and the rest are empty pins. The 9-pin current signal is the signal input. The copper wire of the shielding layer of the control wire should be welded to the DC power ground wire. Be careful not to connect with other pins. The terminals are short-circuited to avoid malfunction or possible burnout of the module.
There are numbers on the module control port socket and the control line socket, please correspond one by one, and do not reverse the connection. The above six ports are the basic ports of the module, and the other ports are special ports, which are only used in products with multi-functions. The remaining feet of ordinary pressure regulating products are empty.
4. Comparison table of the function of each pin and the color of the control line
Pin function pin number and corresponding lead color 5-pin connector 9-pin connector 15-pin connector +12V5 (red) 1 (red) 1 (red) GND4 (black) 2 (black) 2 (black) GND13 (black) 3 (black and white) 3 (black and white) CON10V2 (medium yellow) 4 (medium yellow) 4 (medium yellow) TESTE1 (orange) 5 (orange) 5 (orange) CON20mA 9 (brown) 9 (brown)
5. Meet the necessary conditions for the work of the SCR module
The following conditions must be met in the use of the module:
(1) +12V DC power supply: the working power supply of the internal control circuit of the module.
① Output voltage requirement: +12V power supply: 12±0.5V, ripple voltage is less than 20mv.
② Output current requirements: products with nominal current less than 500 amperes: I+12V> 0.5A, products with nominal current greater than 500 amperes: I+12V> 1A.
(2) Control signal: 0～10V or 4～20mA control signal, which is used to adjust the output voltage. The positive pole is connected to CON10V or CON20mA, and the negative pole is connected to GND1.
(3) Power supply and load: The power supply is generally grid power, with a voltage below 460V or a power supply transformer, connected to the input terminal of the module; the load is an electrical appliance, connected to the output terminal of the module.
6. The relationship between the conduction angle and the output current of the module
The conduction angle of the module is directly related to the maximum current that the module can output. The nominal current of the module is the maximum current that can be output at the maximum conduction angle. At a small conduction angle (the ratio of output voltage to input voltage is very small), the output current peak value is very large, but the effective value of the current is very small (DC meters generally display the average value, and AC meters display non-sinusoidal current, which is smaller than the actual value) , But the effective value of the output current is very large, and the heating of the semiconductor device is proportional to the square of the effective value, which will cause the module to heat up or even burn. Therefore, the module should be selected to work above 65% of the maximum conduction angle, and the control voltage should be above 5V.
7. Selection method of SCR module specifications
Considering that thyristor products are generally non-sinusoidal currents, there is a problem of conduction angle and the load current has certain fluctuations and instability factors, and the thyristor chip has poor resistance to current impact, so it must be selected when the module current specifications are selected. Leave a certain margin. The recommended selection method can be calculated according to the following formula:
I>K×I load×U maximum∕U actual
K: safety factor, resistive load K= 1.5, inductive load K= 2;
Iload: the maximum current flowing through the load; Uactual: the minimum voltage on the load;
Umax: the maximum voltage that the module can output; (three-phase rectifier module is 1.35 times the input voltage, single-phase rectifier module is 0.9 times the input voltage, and the other specifications are 1.0 times);
I: The minimum current of the module needs to be selected, and the nominal current of the module must be greater than this value.
The heat dissipation condition of the module is directly related to the service life and short-term overload capacity of the product. The lower the temperature, the greater the output current of the module. Therefore, a radiator and fan must be equipped in use. It is recommended to use products with overheating protection. If there are water-cooled heat dissipation conditions, water-cooled heat dissipation is preferred. After rigorous calculations, we have determined the radiator models that different models of products should be equipped with. It is recommended to use the radiators and fans matched by the manufacturer. When the user prepares it, select it according to the following principles:
1. The wind speed of the axial flow fan should be greater than 6m/s;
2. It must be able to ensure that the temperature of the cooling bottom plate is not greater than 80℃ when the module is working normally;
3. When the module load is light, the size of the radiator can be reduced or natural cooling can be adopted;
4. When natural cooling is used, the air around the radiator can achieve convection and appropriately increase the area of the radiator;
5. All screws to fasten the module must be tightened, and the crimping terminals must be firmly connected to reduce the generation of secondary heat. A layer of thermal grease or a thermal pad the size of the bottom plate must be applied between the module bottom plate and the radiator. In order to achieve the best heat dissipation effect.
8. Installation and maintenance of thyristor module
(1) Coat a layer of thermally conductive silicone grease on the surface of the module’s heat-conducting bottom plate and the surface of the radiator evenly, and then fix the module on the radiator with four screws. Do not tighten the fixing screws at a time. Evenly, repeat several times until it is firm, so that the module bottom plate is in close contact with the surface of the radiator.
(2) After assembling the radiator and fan according to the requirements, fix them vertically to the proper position of the chassis.
(3) Tie the copper wire tightly with the terminal head ring tape, preferably immersed in tin, then put on an insulating heat-shrinkable tube, and heat it with hot air to shrink it. Fix the terminal end on the module electrode and maintain a good plane pressure contact. It is strictly forbidden to crimp the copper wire of the cable directly on the module electrode.
(4) In order to prolong the service life of the product, it is recommended to maintain it every 3-4 months, replace the thermal grease, remove the surface dust, and tighten the crimping screws.
The company recommends module products: MTC thyristor module, MDC rectifier module, MFC module, etc.