Solid State Relay is referred to as SSR. It is a new type of non-contact switching device composed entirely of solid electronic components. It uses high-power triodes, power field effect transistors, one-way thyristors, two-way thyristors and modules among other electronic components. It has unique switching characteristics and can connect and disconnect electrical circuits without contacts or sparks. It is also called a contactless switch. SSR is generally a four-terminal active device, including two control terminals and two output terminals. Input and output terminals are reliably isolated. When a control signal is applied to the input terminal, the output terminal switches on or off.

Input signals are compatible with computer terminals and digital logic circuits

There is optical isolation between the input circuit and the output circuit, and the isolation withstand voltage is 2500V.

There are two specifications: zero-crossing trigger and random trigger.

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1. Reasons for some failures of solid state relay coils:

1. The reason why the coil often disconnects: whether ultrasonic waves are used to clean the solid-state relay, or an overvoltage is added to the coil, which may cause the coil to disconnect.

2. The cause of the failure of insufficient power provided by the coil: First, the voltage of the solid-state relay coil needs to be confirmed. If the voltage supplying the coil is less than the operating voltage, the contact will not operate.

SSR series solid state relays are made of flame-retardant engineering plastic shell, sealed with epoxy resin, and wired with patterned terminals. They have high structural strength, strong impact resistance, strong vibration resistance, small input drive current, and can be easily interfaced with computer terminals and digital control circuits. , widely used in petrochemical equipment, pharmaceutical machinery, food machinery, packaging machinery, textile machinery, plastic machinery, CNC machine tools, entertainment facilities and other automation control fields.
It is especially suitable for harsh environments such as corrosion, moisture and dustproof, explosion-proof requirements, and occasions with frequent switching.

Solid state relays have high reliability: there are no mechanical parts inside the SSR, and the structure adopts a potted fully enclosed structure. Therefore, SSR has the characteristics of vibration resistance, moisture resistance, corrosion resistance, long life and reliable operation. Solid state relays have low noise: AC SSRs all use zero-crossing trigger technology, so they can effectively reduce dv/dt and di/dt in the line. Solid state relays have fast switching speeds: SSR switching speeds are much faster than mechanical switches. , the turn-on and turn-off times of DC solid-state relays can reach tens of microseconds. SSR has the advantage of being compatible with logic circuits such as TTL and CMOS.

Resistive loads cannot exceed 60% of rated current.
Inductive or capacitive loads cannot exceed 40% of the rated current.
The motor load cannot exceed 20% of the rated current.