What is a solid state relay?
Solid State Relay (ABBREVIATED SSR) is a contactless switch composed of microelectronic circuits, discrete electronic devices and power electronic power devices. The isolation device is used to realize the isolation between the control end and the load end. The input of the solid-state relay uses tiny control signals to directly drive the heavy current load.
A solid-state relay is a new contactless switching device composed entirely of solid-state electronic components. It uses the switching characteristics of electronic components (such as switching triode, bidirectional thyristor and other semiconductor devices) to achieve the purpose of connecting and disconnecting circuits without contact and without spark. Therefore, it is also called a "contactless switch".
The solid-state relay is a four-terminal active device, in which two terminals are input control terminals, and the other two terminals are output controlled terminals. It has both amplification driving effect, and isolation effect, is very suitable for driving high-power switching actuator, higher reliability than an electromagnetic relay, and no contact, long life, fast speed, small interference to the outside world, has been widely used.
Features of solid state relays
Solid state relay with an isolation function is a non-contact electronic switch, with no mechanical contact parts in the process of a switch, so the solid state relay, besides having the same function as the electromagnetic relay is also compatible with the logic circuit, resistance to vibration, mechanical shock, install location is unrestricted, has the good moistureproof mildew corrosion resistance performance, the performance in terms of explosion-proof and prevent ozone pollution is also good, Low input power, high sensitivity, low control power, good electromagnetic compatibility, low noise and high operating frequency.
(1) Solid state relay has no mechanical parts inside and adopts a fully sealed perfusion structure. Therefore, solid state relay has the advantages of vibration resistance, corrosion resistance, long life and high reliability, and its switching life is up to 10.1 million times;
(2) Low noise: the ac solid-state relay adopts the zero-crossing trigger technology, so it effectively reduces the voltage rising rate DV/DT and current rising rate DI/DT values on the line, so that the solid-state relay has minimal interference to the mains when it works for a long time;
(3) Short switching time, about 10ms, can be used in high-frequency occasions;
(4) Photoelectric isolation is used between the input circuit and the output circuit, and the insulation voltage is above 2500V;
(5) Low input power consumption, compatible with TTL and COMS circuits;
(6) The output end has a protection circuit;
(7) Strong load capacity.
Advantages of solid state relays
(1) the high life, high reliability, no mechanical parts, solid-state relay contact functions performed by solid-state relay devices, because there is no movement of the parts, so can in high shock, vibration environment, due to the inherent characteristics of the composition of the solid-state relay components, determines the long life of the solid-state relay, high reliability.
(2) High sensitivity, small control power and good electromagnetic compatibility: solid-state relay has a wide range of input voltage and low driving power, which can be compatible with most logic integrated circuits without adding buffers or drivers.
(3) Fast conversion: solid-state relay adopts solid devices, so the switching speed can be from a few milliseconds to a few microseconds.
(4) Small electromagnetic interference: solid state relay has no input "coil", no touch ignition arc and rebound, thus reducing electromagnetic interference. Most AC output solid-state relays are zero-voltage switches that turn on at zero voltage and turn off at zero current, reducing sudden interruption of a current waveform and thus reducing switching transient effects.
Disadvantages of solid-state relays
(1) after the conduction of the tube pressure drop, SCR or bidirectional control silicon forward step-down up to 1~2V, the saturation voltage drop of high-power transistors is also between 1~2V, the general power field effect tube conduction resistance is also larger than the contact resistance of mechanical contacts.
(2) After the semiconductor device is shut off, there can still be several microamps to several milliamps of leakage current, so the ideal electrical isolation can not be achieved.
(3) The volume of high-power solid-state relays is much larger than electromagnetic relays with the same capacity, and the cost is also high, due to the large tube pressure drop and larg.
(4) The temperature characteristics of electronic components and the anti-interference ability of electronic circuits are poor, and the radiation resistance is also poor. If no effective measures are taken, the reliability of the work is low.
(5) Solid-state relays are very sensitive to overloading, so they must be protected by fast fuses or RC damping circuits. A load of solid state relay is obviously related to the ambient temperature, and the load capacity will decrease rapidly when the temperature increases.
(6) The main deficiencies are the on-state voltage drop (corresponding heat dissipation measures are needed), the off-state leakage current, AC and DC can not be used, the number of contact groups is small, in addition, over current, over-voltage and voltage rise rate, current rise rate and other indicators are poor.ve power consumption and heat generation after conduction.
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Juzlong Electric Co., Ltd. is a high-tech industry integrating research, development and sales. The main products include time relay, small intermediate relay, solid state relay, temperature control instrument, counter, microcomputer time control switch and other piezoelectric devices.
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