Excessive Low Mains Voltage (Mainsguard) - Philips Xitanium LED Xtreme SR Design-In Manual

Input current and power vs. input voltage
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140
120
100
80
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40
20
0
80 100 120 140
Current Power
Illustrative graph of the MainsGuard feature. Shown values are example values.
Please refer to the driver datasheet for exact values.
Design-in Guide - Philips Xitanium LED Xtreme SR driver
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Voltage

Excessive low mains voltage (MainsGuard)

Previously, LED Xtreme drivers would turn off the output in case of
excessive low mains voltage. Depending on the exact driver type a
shutdown would occur between 150 ... 180VAC.
This shutdown functionality was intended to prevent overcurrent
conditions in the mains grid. Without shutdown the driver input
current would increase proportionally with decreasing mains
voltage since the driver is designed to maintain full light output of
the luminaire and thus output power. This would exacerbate
the undervoltage condition further. Consequently, mains cables
and relays may be overloaded and melting fuses and/or MCBs may
trip.
In order to prevent overcurrent conditions, a shutdown mechanism
had been implemented in the driver. However, the main
disadvantage of this shutdown is total loss of lighting.
Xitanium LED Xtreme SR drivers have a feature incorporated to
protect luminaire and mains grid against overcurrent conditions
without loss of lighting. This smart feature is called MainsGuard. Its
function is to proportionally decrease input current as function of
decreasing mains voltage and to keep doing so all the way down to a
much lower mains voltage before the driver output is ultimately shut
down. A small hysteresis of 5 ... 10V against on/off nuisance cycling is
implemented before the driver output becomes automatically active
again once the mains voltage starts to recover (no mains power
cycle required).
A general graphical representation of MainsGuard can be seen in the
100
90
illustration on the left. Exact values can be found in the MainsGuard
80
70
graph in the driver datasheet.
60
50
40
Main benefits of MainsGuard are:
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20
10
0
• Light will remain on, even at excessive low mains voltage
• Luminaire and grid are protected against undervoltage and
overcurrent
• No current overloading of MCBs, fuses and relays
Note: the voltage levels at which output power is reduced and the
output is eventually shut down and re-activated are fixed and
cannot be modified.
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