? Supply solid state relays Selection - Zhejiang Kun two crystal SSVR25A

How to choose the SSR model specifications mainly by selecting the appropriate rated current solid state relay (SSR) except where otherwise noted, rectification, and controllable power module versa. Depending on the load type to choose SSR rated current. Resistive load, inductive load and capacitive load when just starting transient current is large. Even purely resistive, since having a positive temperature coefficient, cold resistance value is small, and thus a larger starting current. When electric current is 1.3-1.4 times just turned stable when. When the incandescent lamp is turned on steady-state current of 10 times. Some metal halide lamp not only open up to 10 minutes, and there are up to 100 times the pulse current steady state. Induction motor starting current is 5-7 times the rated DC motor starting current bigger. Moreover, inductive load also has a high back EMF. This is an uncertain value, with different L and di / dt and different. Typically 1-2 times the power supply voltage, so that the power supply voltage and superimposed. There are up to three times the supply voltage. Capacitive loads with greater risk, because when you start, the voltage across the capacitor can not change suddenly, a capacitor (load) is equivalent to a short circuit. This load must pay special attention in the selection. Of particular note is that users do not rush current value as a selection SSR load starting current basis. SSR surge current value is based Thyristor Surge current standards. It is a prerequisite for half (or one) power cycle. That is, 10 or 20ms. The preceding boot process, ranging from a few hundred milliseconds, minutes, and up to 10 minutes more. This is sure to please close attention. Selection Method 1. In the selection of the solid state relay of small current size of the printed circuit board used, because of the lead terminals is high thermally conductive material, welding should be at a temperature less than 250 ℃, less than 10S conducted under conditions, such as consideration of the ambient temperature The reason, if necessary, consider derating generally control the use of the load current is within the rated 1/2. [2] 2. Various load surge of choice for solid state relay SSR charged instantly connected load will have a huge surge current, due to the heat too late to distribute, is likely to SSR SCR damage inside, so users response characteristic of the controlled load surges in the selection of the relay for analysis, and then select the relay. The relay in the premise of ensuring steady work can withstand the surge current, the choice can refer to Table derating factor (room temperature) load of 2 variety. As the choice of relay need to work more frequent occasions when high reliability requirements of working life and should be on the basis of Table 2, multiplied by 0.6 in order to ensure reliable operation. General in the selection above principle, in the low voltage requirements signal distortion small can choose FET used as an output device DC solid state relay device; such as AC resistive load and inductive load most of the optional relays used zero, this would extended load and relay life, but also reduce their RF interference. Such as the phase output control should be used in a random type solid state relays. Load capacity 3. Influence of ambient temperature solid state relays greatly influenced by the ambient temperature and self heating, and in the installation process, you should ensure that they have good heat dissipation, rated current 10A above products should be equipped with heat device, 100A more products should be equipped with forced cooling fan radiator added. Note that relay good contact with the radiator bottom should be installed and consider the appropriate amount of thermal grease applied to achieve the best cooling effect. If the relay long-term maximum output current and ambient temperature profile data at a high temperature (40 ℃ ~ 80 ℃), the user can be provided according to the manufacturer, consider derating to ensure proper operation. 4. overcurrent, overvoltage protection measures when relays due to over-current and load short can cause internal solid state relay output SSR SCR permanent damage, and may consider increasing the fuse air switch to be protective in the control loop ( Select relay output protection should select products, built varistors and RC snubber circuit buffer, absorbing the surge voltage and increase dv / dt tolerance); also available in relay output and connected RC snubber circuit and varistor (MOV) to achieve the output protection. Selection principle is the choice of 500V-600V 220V varistor optional 800V-900V varistor at 380V. 5. relay input circuit signal when the input voltage is too high or the use of the input current is too large and exceed the parameters of its provisions can be considered in series with the input voltage divider resistors or the input port and the shunt resistor connected to the input signal does not exceed the rated parameter values. 6 In the specific use, control signals and load power for stability, volatility should not be greater than 10%, otherwise the regulator should take action. 7. The installation should be used away from electromagnetic interference, radio frequency interference source, to prevent runaway relay malfunction. 8. Solid state relays open and load side voltage, the output terminal will be some leakage current, use or design should pay attention to. 9. Failure to replace the solid state relays, should try to use the original type or technical parameters identical products in order to match the original application circuit to ensure reliable operation of the system. AC solid state relay switch mode divided by zero-voltage turn-based (the zero-crossing) and random turn-based (the random type); divided by the output switching element triac output type (ordinary) and unidirectional SCR anti-parallel type (enhanced); divided according to the installation on the printed circuit board with the pin plug (natural cooling, do not take the heat sink) and fixed to a metal base plate device type (by radiator cooling); In addition there are a wide range of inputs input (DC3-32V) constant current source type and serial current limiting resistor type. SSR solid state relays to trigger form, can be divided into zero-pressure (Z) and phase modulation type (P) two kinds. Upon application of an appropriate control signal input terminal VIN, P-type SSR immediately turned on. When the VIN revoked when the load current is less than triac holding current (AC commutation) SSR off. Z-type SSR interior includes a zero-crossing detection circuit, upon application of the input signal VIN, only when the load supply voltage reaches the zero-crossing area SSR to conduction, and is likely to cause the maximum delay of a half cycle of the power supply. Z-type SSR shutdown condition with P-type, but because the work load current is approximately sinusoidal, harmonic interference, so widely used. SSR thanks to different output devices, a common type (S bidirectional thyristor) and Enhanced (HS unidirectional thyristors) points. When added with inductive load, the input signal is off before t1, the triac is turned on, the power supply voltage 90O (pure sensation when) the current lag. t1 time input control signal revoked, triac holding current in shutdown is less than (t2) SCR will withstand voltage rise rate dv / dt high reverse voltage. This voltage will triac internal junction capacitance, positive feedback to the gate. If more than triac commutation dv / dt index (typical 10V / s will lead to change for a long time to recover or even failure. Unidirectional thyristor (Enhanced SSR) due in unipolar operation, this time only Static rate of voltage rise is limited (typically 200V / s), and that consequently enhanced solid state relay SSR HS series than the ordinary type of commutation dv / dt index an increase of 520 times. As a result of two-way high-power thyristor trans in parallel, changing the current distribution and thermal conditions, and improve the SSR output. Enhanced SSR in high power applications, either resistive or inductive load load resistance, voltage, resistance to current impact and reliability of products, more than ordinary solid state relays and achieve the basic indicators of imported products, is an alternative to ordinary solid state relays update product selection SSR SSR load and general load should be no problem, but it must also consider some special load conditions, in order to avoid excessive the impact of current and over-voltage, device performance caused by "cold resistance" feature unnecessary damage. incandescent lamp, electric and other categories, resulting in the opening moment of the surge current over the rated operating current value multiple of ordinary type SSR, may Press 2/3 to choose the current value. Enhanced SSR, according to the manufacturer's choice of parameters of industrial control under adverse field conditions, it is recommended with sufficient voltage, current margin. Certain types of lamps in blown instantly appears low impedance. gasification and discharge channels and capacitive load, such as a capacitor bank or capacitor switching power supply, will result in similar short-circuited. may further series resistance or inductance in the line, limiting measures as a motor to open and close , will have a greater impact on current and voltage relays, solenoids pull jitter caused by unreliable, and a capacitor commutated motor commutation capacitor voltage and the supply voltage superposition produces two ends of the SSR fold surge voltage supply control primary transformer should also consider the impact of transient voltage on the secondary line to the primary. In addition, the transformer is also possible because the current asymmetry in both directions, causing abnormal surge current caused by saturation The above case, the SSR application specific load, the number becomes a little complicated. feasible way is through an oscilloscope to measure current and voltage surges can cause, so choose the appropriate SSR and protection measures in the next accused load through instant will have a great inrush current due to the heat too late to distribute, is likely to SSR SCR damage inside, so users respond to the surge in the selection of the relay controlled load characteristics were analyzed, and then choose a relay. relay Under the premise of ensuring steady work can withstand the surge current, the choice can refer to Table derating factor (at room temperature) load of 2 variety, such as the choice of the relay need to work more frequently, life, and reliability requirements more When the case of high work should be on the basis of Table 2, multiplied by 0.6 in order to ensure reliable operation generally followed in the selection of the above principles, the low voltage requirements signal distortion small can choose FET used as an output DC solid state devices relay; if the AC resistive load and inductive load most of the optional relays used zero, so the load and extend the life of the relay, also reduce their RF interference. Such as the phase output control should be used in a random type solid state relays.