Solid State Relays
Standard production of the solid state relays is divided into three main groups:
1. Zero-crossing relays
The zero crossing relays pick-up when the output voltage is near to zero and always drop-out at zero-current. They are particularly suitable for the commutation of resistive and capacitive loads.
2. Instant commutation relays
The instant commutation relays pick-up simultaneously to the input signal and then at each point of the sinusoidal output voltage curve and drop-out at zero-current. They are particularly suitable for the commutation of inductive loads.
3. D.C. commutation relays
The relays for D.C. load commutation pick-up and drop-out simultaneously to the control voltage.
The solid-state relays can particularly be used where a high commutation frequency is required together with the possibility of commutating, by means of limited control voltage (3 V-3 mA), high currents (90 A-480V) with 4 KV insulation between input-output. They are extremely resistant to vibrations or oxidation as well as to mechanical impacts and do not cause arcs nor fluctuations.
All the solid state relays are provided with a snubber filter, which protects them from any undesirable spikes caused by an excessive speed of the output voltage. However, in certain applications, it has been found that the device is still not protected, as a result of the elevated voltage spikes which may sometimes be present in industrial environments. In such cases, a varistor must be applied to the device, in parallel with at the output, so as to protect the device from the above said spikes. To protect the devices from overcurrents, it is recommended that a fast-reacting fuse be installed for each phase, rather than a normal fuse which would only intervenes once the device has already been damaged.
EC REFERENCE STANDARDS:
Low Voltage Directive (LVD) 2006/95/EC
Electromagnetic Compatibility (EMC) Directive 2004/108/EC
– Low power supply
– Zero crossing or instantaneous commutation
– Life duration/reliability
– Reduced response time
– No mechanical part in movement no recoil
– No mechanical wear
– Compatibility with digital circuit
– Shock resistance
– Noiseless working
– Artight seal
– Drooping (from 1 to 1,5V)
– Only A.C. or D.C. exit output
– Dissipation’s frequent obligation
– Utilization with small signals
– Resistance to transient voltage
– Runaway current