A solid state relay (SSR) or solid state contactor is an electronic switching device that uses an electronic component switching element instead of an electromechanical contact to make or break the connection in the load circuit.
Benefits of solid-state relays
Our solid state relays have several features that distinguish them from other switching devices:
They are built with higher levels of reliability and performance to drive standard resistors, inductors or transformers.
They offer exceptional life expectancy due to selected electronic components.
They have no internal resistance and can therefore switch at higher speeds without overheating.
Our solid state relays fit in tight spaces where larger switches cannot be installed.
They easily replace all your mechanical relays.
They tolerate high overcurrent loads and respond to repeated stresses and high temperatures.
Technical advantages of solid-state relays
Easy to install
Modular design
Panel or DIN rail mounting
Quiet operation
Accurate and reliable
Low electromagnetic emissions
High switching frequency
Long service life
What is a solid state relay?
SSRs (solid state relays) are designed to control high-power AC electrical loads with a low-voltage input signal.
These electronic components enable AC or DC electrical current to be switched without mechanical movement.
They are generally used in systems where PLCs or microcontrollers cannot provide the required power management capability.
It is a competitive product category to electromechanical relays and other switching methods.
There are two SSR technologies:
Hybrid Solid State Relay:
The hybrid solid state relay uses an optocoupler along with conventional thyristor technology to provide higher isolation and current ratings.
Optoelectronic solid-state relays :
These relays use an opto coupler as the essential isolation element, and employ discrete power MOSFETs, IGBTs or thyristors for higher current ratings.
What is the design of a solid state relay?
The basic internal structure of an SSR consists of several main components:
The input interface, used to optically isolate the circuit from the output of the input.
A control section acts as an optical isolator. It often consists of one or two light-emitting diodes (LEDs) for emission. For receiving, one or more photosensitive elements such as photodiodes or phototransistors are used. These elements close the circuit and allow current to flow to the load.
A power part with a switching element, usually a thyristor such as a TRIAC, an SCR, a GTO thyristor, but FETs and triacs are also used to switch the loads.
How does a solid state relay work?
Solid state relay operation uses solid state devices such as transistors, thyristors or MOSFETs instead of electromechanical devices such as relays to switch high power resistive or inductive loads.
How to drive a solid state relay?
SSRs are controlled by a small external voltage applied to their control terminals. This signal can be an AC or DC voltage. A low power circuit can be used to switch the controls of AC or DC supplies to a high power load.
A temperature controller PXE or a PID PXF controller provides voltage and DC control of the solid-state contactor to regulate the temperature. The temperature controller is responsible for switching the SSR on and off in response to temperature changes. To control the SSR correctly, the temperature controller must be correctly selected. Otherwise, the SSR may fail to switch on or off at the correct temperature, which can damage sensitive equipment or present a safety hazard. In addition, temperature controller must be able to handle the current required by the solid-state relay.
When to use a solid state relay?
You can use this component to switch AC or DC loads from a low voltage or current. The solid-state relay, often considered the modern equivalent of the mechanical contactor, offers many advantages. It is particularly useful where protection against overvoltage is crucial. This device offers control without moving contacts, reducing the risk of wear and maintenance. Thanks to its contactless function, it is ideal for circuits requiring silent, spark-free switching.
Another key advantage is its ability to handle multi-phase loads, making it suitable for a wide range of industrial applications. The solid-state relay is easy to connect, usually with screws or wires, and can be fitted with a heatsink to manage heat dissipation. In special cases, where fast, precise control is required, solid-state relays offer reliable, consistent results. In terms of selection, there are many options available on our product page to meet your specific current and voltage requirements.
Finally, this type of solid-state contactor is frequently recommended in technical applications for its robustness and ability to provide optimum protection in a variety of control circuits.
What are the applications of solid state relays?
Solid state relays are commonly used in industrial processes and machine automation. One reason for this is their ability to switch high voltages and currents, as well as their resistance to shock and vibration. This makes them ideal for environments with a lot of movement or harsh conditions.
These products can also be used in processes where precision is important, such as in medical equipment or data acquisition systems. In addition, they are often used in areas where space is limited. As a result, solid-state relays have a wide range of applications, including :
Electric heating control systems
Temperature control for electric ovens.
Power controllers for electric motors
Temperature control for packaging machines
Industrial automation and energy management
What are the advantages of solid-state relays?
Solid state relays (SSRs) have several advantages over electromechanical relays (EMRs). Here are some of the advantages that make SSRs more attractive than EMRs:
Higher input/output isolation than mechanical relays.
High speed switching.
Low power consumption.
No moving parts.
Long life, estimated in some cases at 10 million operations.
High resistance to shock, vibration and noise.
No contact bounce.
Fast on/off time.
High noise immunity due to no contacts.
Low drive power required.
Low electromagnetic interference.
Can have multiple outputs;
Control of resistive or inductive loads.
For all these reasons, solid-state relays are the preferred choice in many applications where reliability and precision are essential.
For these reasons, solid state relays are the preferred choice in many applications where reliability and accuracy are essential. Among the disadvantages of these products is their higher price. However, this disadvantage is often offset by the many advantages of SSRs.
Long service life
High-speed switching
Heavy-duty
How to choose your solid-state relays
The first thing you need to know when selecting your solid state relays is to check the type of input and output:
Is it alternating or direct current (ac dc)?
Do they have current or voltage control?
What is the current rating of the relay load?
What is its operating voltage?
What is the type of resistive or inductive load?
How many circuits or phases must be switched?
Then there are other important technical features to consider:
the switching time,
the isolation of the input and output,
control voltage,
operating temperature and heatsink requirements,
inrush currents at start-up for certain loads,
risks of overvoltage depending on their application and conditions of use.
diagnostic functions such as load break or short-circuit.
type of installation (panel mounting, plug-in), packaging (DIN rail).
You should also check the maximum dimensions (length x width x height), output noise and protection features. And don't forget the contact resistance!
