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Chapter 12 Helpful information
Power Generator and UPS units
In order for a UPS unit to function properly with a Power Generator the slew of the UPS unit
needs to be considered and the Power Generator needs to be adjusted accordingly. The slew
rates of the UPS units is listed in the below table.
UPS Name
RT8kVA 6U Rack or Tower UPS
(200-240VAC)
RT8kVA 6U 3:1 Phase Rack or
Tower UPS (380-415VAC)
RT11kVA 6U Rack or Tower UPS
(200-240VAC)
RT11kVA 6U 3:1 Phase Rack or
Tower UPS (380-415VAC)
The slew rate allows the UPS to synchronise to the utility power or the power supply.
In order for the UPS to transfer to bypass under fault, the UPS automatically synchronises its
waveform to follow the supply.
If the supply changes, the slew rate is the rate the UPS speeds up or slows down its frequency
to match the supply. This speed is limited to avoid damage to the load by the UPS changing
speed too fast.
When the Generator is feeding a UPS, the UPS can follow it within its slew rate and frequency
limits. Outside of this, the UPS will alarm that the bypass is out of tolerance, as it cannot make
a no break transfer.
The tolerance of the bypass is narrow as it is within the limits to feed the load. The tolerance of
the rectifier may be far larger, therefore does not necessarily mean the UPS will switch to
battery.
Considerations
1. Assess the generator frequency. Every UPS has a set input voltage and frequency
window that, if exceeded, will cause the UPS to go onto battery. If a generator's
frequency range is too wide for the UPS to accept, the UPS may interpret the generator
220
Machine Type and
Model
5594-8KX
5594-8PX
5594-9KX
5596-9PX
Slew Rate HE Mode Slew Rate
1 Hz / s
0.5 Hz / s
1 Hz / s
0.5 Hz / s
1 Hz / s
0.5 Hz / s
1 Hz / s
0.5 Hz / s
6U Rack or Tower UPS RT8kVA and RT11kVA IUOMG
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