Solid state relay (SSR)

There are many advantages of solid-state relays compared to mechanical relays and contactors:

• High switch cycles
• Long service life because no mechanical parts and therefore less wear
• Compact dimensions
• Low actuation power
• Short response times
• Silent
• Lower power supply requirements
• Good practical solutions for heat dissipation
• Bounce-free load-switching with neither arcs nor fluctuations
• Resistant to vibrations and mechanical impact
• Increases the lifetime of electric heating elements considerably, compared to mechanically relays

The ELOTECH palette ranges from simple industrial solid-state relays for circuit boards or screw assembly to solid-state relays for DIN rail assembly, with or without heat sinks. Further variants offer additional current monitoring and alarm outputs. Depending on the control, there are corresponding SSRs for phase angle control and pulse group control.

There are three basic variants:

1. Solid-state relays with logic actuation:
   1. Through-switching solid-state relays: These relays energise when the output voltage is close to zero and always de-energise at zero current. It is always complete shafts that are connected or disabled. They are particularly suitable for switching ohmic and capacitive loads.
   2. Randomly switching solid-state relays: Through-connection whenever a control signal is present, not necessarily in 0-pass.
2. Solid-state relays for leading edge phase control: This relay type switches with the input signal and cuts off at any point of the sinusoidal output voltage curve, thereby controlling the power. Use particularly with inductive loads.
3. Solid-state relays with burst-firing operation: This relay type always switches complete sinusoidal waves on or off, to control the power. This type of control does not generate harmonics and so saves excess load on the grid.

SSR range:

• Control power supply at least 3 V or 3 mA
• High currents up to 90 A and 480V with 4 KV insulation between input and output (custom version with DC)
• 2/3-phase also possible

The right use and the right switching ensure a long service life

• All solid-state relays are equipped with special filters. These filters protect against rapid voltage fluctuations. Especially in industrial environments, however, such voltage peaks can be stronger, so a varistor should be connected in parallel with the output.
• To protect the circuitry from current peaks, we recommend a fast-acting fuse for each phase.
• To guarantee the optimal performance of the solid-state relay it needs to be in a well-ventilated environment. Avoid placing SSRs one above the other.