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SOLID-STATE RELAYS

The EL.CO. 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 outputvoltage is near to zero and always drop-out at zero-current. they are particularly suitable for commutation fo resistive and capacitive loads.
2- Istant commutation relays
The istant 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 relaysfor D.C. load commutation pick-up and drop-out simultaneously to the control voltage.

RECOMMENDED APPLICATION:
The solid-state relays can particularly be used where hight commutation frequency is required together with the possibility of commutating, by means of limited control voltage (3V- 3mA), hight currents (90A-480V) with 4KV insulation between input-output. They are extremely resistant to vibrations or oxidation as well as to mechanical inpacts and do not cause arcs nor fluctuations.

GENERAL FEATURES:
All the solid state relays are provided with a snubber filter, which protects item from any undesirable spikes caused by on excessive speed of the outputvoltage. However, in certain application, it has been foundyhat the device is still not protected, as a result ofthe elevated voltage spikes which may sometimes be present in industrial enviroments. In such cases, a varistor must be apllied to the device, in parallel with at the output, so as to protectthe device from the above said spikes. To protect the device from overcurrents, it is recommended that a fast-reacting fuse be istalled for each phase, rather than a normal fuse which would only intervenes once the device has already been damaged.


EC REFERENCE STANDARS:
HD419.2 SI / CEI 17.38 / IEC 158-2 CEE 73/23 – 93/68

ADVANTAGES:
- Low power supply
- Zero crossing or istantaneous commutation
- Life duration/reliability
- Reduce response time
- No mechanical part in movementno recoil
- No mechanical wear
- Compatibility with digital circuit
- Shock resistance
- Noiseless working
- Artight seal

LIMITATIONS:
- Drooping (from 1 to 1,5V)
- Only A.C. or D.C. exit output
- Dissipator's frequent obligation
- Utilization with small signals
- Resistance to transient voltage
- Runaway current

INSTALLATION:
To ensure optimal performance from all the solid state relays, it is necessary to place them in well ventilated enviroments which will ensure that the devices have a good dissipation. Futhermore, during the installation, it is important to avoid arranging the relays in rows which are one upon another, this could be jeopardise the good dissipation of the relays.

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