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JAN MAYEN: UPS SYSTEM IN SEISMO ROOM


INTRODUCTION


In order to provide better protection against mains power disruptions and outages, we want to install UPS ("Uninterruptible Power Supply") in the Seismo room, covering these units:

  1. Linux industrial PC, which will execute an orderly shut-down sequence when the available run time has nearly expired.
  2. Power supply (approx. 48 Vdc) that feeds equipment in Trolldalen - Trillium seismometer, Titan accelerometer, DM24 digitizer, units for two telemetry channels - including telemetry units mounted in Seismo rack.
  3. Power supply 12 Vdc that feeds VHF radio receivers, demodulators and digitizer units that process signals from the remote JNE-Ulla and JNW-Liberg seismometers.

The UPS should provide at least 30 minutes back up time. It should have RS232 port which enables proper shutdown of connected equipment, if desired.


POWER REQUIREMENT OF PROTECTED EQUIPMENT


In order to estimate back-up time that a specific UPS will provide we first need an estimate of power consumption of the connected equipment.

Unit Description Power [W]
Power supply #1 (48 Vdc) Trolldalen (0.9A*48V) + PS internally 55
Power supply #2 (12 Vdc) Digitizer DM24 in rack (0.3A * 12V) + VHF receivers + demod unit ("PTS") 5
Industrial Linux box - 40
Monitor - (25) (not included)
TOTAL POWER CONSUMPTION: 100


UPS SELECTED


Product details


Runtime


From the "Runtime vs Watt" curve on the manufacturer product link above, we should have 50 minutes UPS backup time with 100 Watt load. A very large proportion of "normal" power outages should be covered by this duration.

APC-SMT750I: Runtime vs load.
UPS runtime vs. load for APC mod SMT750I (source).

With the 6.6 Jan Mayen earthquake in August 2012 in mind, one could also envision damages to the diesel electrical generators at the base, causing power cuts of much longer duration. There are three such generators, so one will probably be operational after a large earthquake; and even if power should be unavailable for several days, for how long should we aim to record data in such a scenario?

We could of course double or treble the UPS backup time by selecting other members of this APC UPS family: http://www.apc.com/products/family/index.cfm?id=165&tab=models (select 100W in the pull-down menu, and back-up time for each model will be displayed in column below)

Serial communication protocol


The SMT750I is furnished with two communication ports. Appropriate serial cables are part of the delivery. One port - the RJ-type (like on Ethernet ports) is direct RS232. The other is USB and, when connected to USB port on a PC, appears as a serial communication channel.

The serial communication protocol is manufacturer proprietary. There is both Windows and Linux software available (called PowerChute Business Edition) to utilize the remote communication capabilities of the unit. APC technical support can be contacted if information on specific protocol details is required, e.g. in order to implement a simple Linux cron job that periodically interrogates the UPS and executes an orderly shutdown sequence, if backup time is about to expire.

Spare parts and accessories



INSTALLATION


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Page last modified on September 06, 2018, at 04:48 PM
Electronics workshop
Department of Earth Science - University of Bergen
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