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LED blocks: When, How, Which surge suppressors to implement.

Goals and Symptoms

LED blocks:
When, How, Which surge suppressors to implement.

Facts and Changes


Causes and Fixes

- When to implement surge suppressors :

If the LED is exposed to high voltage, short term spikes such as those created when large coils are de-energised ( solenoids, large contactor etc.) then damage may occur to the circuitry, causing a premature failure of the device. This damage can also occur where the inrush to the coil is high.

The catalogue characteristics state that where the pilot light is fitted directly in parallel across an inductive coil, the inrush of the coil must not exceed 30VA. Remember that the inrush of the coil is usually very high compared to the nominal power consumption.
If this value of 30VA is exceeded, then a suppressor block must be used in conjunction with the pilot light. It is also advisable to fit suppression across the inductive load to reduce the back emf produced.

- How to implement surge suppressors :
Connect the suppressor in parallel with the LED block.

- Which surge suppressors to implement :
ZBVJ* and ZBVB* => mostly used on 12Vdc or 24Vdc, the inductive loads are generaly low. However it is recommended to implement a freewheel diode. You can use the ZBZG156 which includes a diode.
ZBVG* (110...120Vac) => Use ZBZVG (maximum power of coil 120VA).
ZBVBG* (24...120V ac/dc) and ZBVM* (230Vac) => Use ZBZVM (maximum power of coil 230VA).

For coils with a power above the suppressors limitation, use a dedicated suppressors on the coil itself:
Freewheel diodes for DC applications.
Bidirectionnal diodes or varistors for AC applications.

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