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There are many kinds of bipolar 24v solid-state relays, but the most commonly used ones are output, input, photodetector, heat sink free, and zero-crossing relays.
An output 24v solid-state relay connects an output electrical load with the corresponding control signal. These help in switching the DC output electrical load. Note that an electric load here means a device that consumes electrical energy, e.g. motor, light, heater.
When it comes to active devices, the type of electric load can be resistive, inductive, or capacitive. But on the bigger picture of the electrical system, output SSRs are often used for the on/off control of the output electric appliances for industrial automation, process control, or other elements of the system.
The input 24v solid state relay is a device that receives a control signal to switch on or off the corresponding output electrical load. But unlike the outputs, these inputs tend to be 0-24V DC control signals, for example, a signal from a PLC (Programmable Logic Controller) or a control panel push button.
Photodetector solid-state relays use light to sense or change signals and, therefore, operate. They come in handy in environments where the electrical activation cannot be used due to high magnetic fields, electrical interference, or noise. The relays operate by using a light –usually infrared – that travels through isolation. This offers two advantages, minimal electrical interference and high isolation voltage between the input and output.
These 24v DC relays, unlike others, can easily be used without a heat sink (fan) for cooling, so they can just as well be used without that extra hassle. In general, heat sinks are necessary to keep the SSR cool and, thus, the operation optimal. SSRs will usually overheat, especially if the device is on for long hours of duty. A heat sink-free relay is designed to operate without one, even under the conditions of a heavy load.
These are solid-state relays that connect to AC loads by first turning the TR off when the applied voltage is at the zero crossing point. They efficiently control AC motors, provide element heating, and light dimmers.
This type of SSR is designed to minimize switching transient voltages and currents that could damage electrical equipment.
They are designed to provide a long service life with minimal maintenance since mechanical components are absent. Therefore, the durability of solid-state components, the materials used in their construction, and their operational environment will greatly impact their durability. The materials will be explained in how they affect their durability.
Semiconductor materials for 24v solid state relay
Since these are relays that operate electronically as opposed to relying on a mechanical switch, they use semiconductors, e.g. silicon or gallium, to construct the internal components. These materials are chosen for their ability to withstand high temperatures and thus ensure high voltage and current conductivity.
This allows the relay to work under different conditions, and they are less likely to fail due to heat or stress as opposed to others.
Packaging materials in a 24v solid state relay
These relays are incorporated with durable enclosures or packages, e.g. polyamide (nylon) or other heat-resistant plastics. They serve to protect the internal components from environmental hazards such as dust, moisture, and chemicals. They can also help with component life extension.
Terminal and conductor materials
The terminals and conductors are made of either copper or copper alloys, and this greatly affects the electrical conductivity, which is what transfers power and control signals between the relay and the system. Copper is a highly resistant metal to corrosion.
Mean time between failures (MBTF)
Like other solid-state devices, SSRs have higher MBTF compared to their electromechanical relay counterparts.
Environmental resistance of 24v solid state relay
Due to the differences in construction, SSRs have greater ruggedness and resistance to vibration, shock, and extreme temperatures. ECRs are usually less durable in harsh and high-temperature environments, so they are less likely to fail because of this.
Cyclic operation and load handling capability
SSRs can easily manage loads and on-and-off cycles for a much longer period (e.g. years) than ECRs without any wear and tear. ECRs will often have a much shorter operational life due to the mechanical wear and tear associated with the opening and closing of the electromechanical switches at each relay cycle.
This particular durability, plus the fact that they perform well in many cycles, makes them ideal for any industrial application.
Automation, industrial machinery, manufacturing and process control
24v SSD relays are used in industrial automation systems. They are used to control heavy loads such as motors, pumps, heaters, and electrical equipment over long periods of time.
Because they are so long-lasting, they make a good choice for machinery that uses frequent on-and-off cycling.
Transportation systems for 24v solid state relay
24v SSDs are used in electrical subsystems in transport, e.g. relay signal systems, train control systems, and vehicle automation. Because of their resistance to extreme conditions, e.g. heat, dust, and vibration, they are a good choice for automotive applications.
Communication systems for 24v solid state relays
In communication systems, 24v SSD relays switch RF signals and antennas, provide power control in telecommunication equipment, and control load for electronic switches. Since these are used in critical applications that require accuracy and reliability, SSRs make a good choice.
Energy systems and other electrical equipment for 24v solid state relay
In energy systems such as power generation, transmission, and distribution systems, these relays will control the switchboard and protect electrical equipment and loads. In particular, zero-crossing SSRs are typically used in power control applications such as light dimmers, heating elements, and motor speed controllers. This is because they minimize electrical transients and thus don't damage the equipment.
Medical equipment for 24v solid state relay
Finally, in the medical field, they are used to control surgical equipment, hospital automation systems (for example, for patient monitoring), and diagnostic imaging systems such as MRI and CT scanners. Because of their fast switching speed and reliability, they became an important part of critical medical applications requiring ultra performance and thoroughness.
There are several factors buyers can consider to ensure the right relay is chosen for an application.
Input control requirements for 24v solid state relay
An input 24v solid state relay requires specific electrical signals to turn on or off. This means that different types of input control signal relays are available that correspond to the specific requirements, e.g. analog or digital, and vary in their input current or voltage.
This also includes the operating temperature range of the components used in the device, especially if used in extreme environments, or the package material/ enclosure design for thermal dissipation. So, to control this, it might be better to go for a heat sink-free relay or one with a more efficient heat sink.
Load type and output configuration of 24v solid state relay
Different relays work well with different types of loads, especially with electric machines. Photodiodes are best for resistive loads, e.g. lamps, heating elements, and fans. Zero-crossing relays are ideal for AC applications such as motor control, cooling fans, and light dimming because they turn off when the voltage is at zero, thus not causing a voltage spike. All output solid-state relay configurations vary in their output current and voltage range specifications. Select one with a sufficiently high range to meet the requirements of the load used, as this will help prevent output overload.
Power handling capability for 24v solid state relay
This includes the maximum output current and voltage the relay can handle, as well as the maximum power it can dissipate without overheating. This is critical to ensure that the relay can adequately support the demands of the system it is used in. Consult a relay operating curve to see how the relay functions in different environments.
Relay installation and application for 24v solid state relay
The SSRs are usually designed for PCB mounting, which makes them convenient to install in electronic devices. There are also standalone relays that can be mounted in industrial enclosures for applications requiring larger or heavier-duty relays. Another thing is that different relays are characterized by varying degrees of electrical isolation, which affects the amount of noise and interference they block. This is especially important in sensitive electronic applications where high precision is required, e.g. medical or aerospace instrumentation.
Since they don't have any moving mechanical parts as electromagnetic relays do, they're more durable than electromechanical ones. In addition, they can handle extreme environmental conditions (for example, high temperatures and a lot of vibrations) and still last long, which is why they are worth it.
The 24v relay operates on low voltage and is most commonly used in automation control systems. However, there are others that work with regular home voltages, so it should be fine. Just make sure the relay used is rated for the proper voltage and current of the appliance to be used and that it can handle the inductive loads to avoid electrical spikes that damage the system.
These relays are usually more reliable since they can easily stand extreme environmental conditions like high temperatures or a lot of vibrations. They also switch faster and are better at electrical isolation, hence more durable.
This will depend on the specific one being used and the operating conditions. Some can run under heavy load for long periods without an extra fan for heat sink, while others do require it to maintain optimal performance and prolong its lifespan.
