Surge protectors for LED drivers function in different ways depending on the installation class of the fixture.
A - First class installations (pole and armour go to the ground)
A protection is implemented on the driver input:
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Between phase and neutral:
A suppressor (varistor) increases the driver's own protection level by providing additional immunity to overvoltages between phase and neutral.
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Between phase and earth and between neutral and earth:
A suppressor plus a gas discharger intervene to eliminate overvoltages that can occur between both poles and earth, keeping the potential difference between both poles and earth within a range of about 2000V.
It is recommended to use a high current fuse (16A) in case the varistor closes in short circuit (excessive loads).
The VPA1500KK1 and VPA1500KK1 protections are equipped with thermal protection which disconnects the load if the internal varistor overheats or goes out of use.