Uninterrupted power supply: Difference between revisions

Revision as of 12:03, 16 April 2013

The problem with uninterrupted power supply divides in some sections:

UPS functional type

Online UPS means, that the output-power ist constantly generated from the battery while the battery becomes constantly loaded from mains power. This concept ensures uninterrupted output-power even in the moment of mains powerfail. Other concepts deliver mainspower and start generation from battery only in case of powerfail. The startup of generation may take some (short) time. So the output-power can have dips or other deformations in the moment of powerfail, which could cause the "load" instruments to stop working.

Choose a high-quality UPS with "online"-generation.

UPS output voltage:

The waveform should be sinewave or stepped approximation to sinewave. The voltage should meet the Oxy-requirements which are 110 or 230V at 50 or 60 Hz with serie A-D according to the setting at the Oxygraph mains input. Serie E and F accept nominal voltages from 100 to 240 V 47 - 63 Hz, due to accepted tolerances of +/- 10 % the maximum range covers 90 - 264 V.

For the waveform of any UPS is only "close" to a sinewave its always a good idea to stay securely within these ranges and not to explore the boundaries. The type of "rectangle"-output UPS and most cheap UPS come with the risk of interference with the loads electronics.

UPS Output maximum current:

The instruments powered by the UPS draw different currents at startup, at running with full load or in normal operation. The UPS needs to limit the current to prevent its internal electronics from damage. This limitation may cause problems with the "load" instruments especially at startup when they need to switch on transformers or to load capacitors, thus drawing inrush-currents.

Therefore an UPS with inrush capability is preferable.

UPS Output thermal current:

The output current will warm up the internal electronics of the UPS, which is designed for a certain maximum of continuous current. All "load"-Instruments together may not reach this value during an experiment.

So the rated UPS output continuous current has to be higher then the sum of continuous current of all connected instruments, including Oxygraphs, computers, monitors.

UPS power failure buffering time

The battery of the UPS in normal operation is fully charged by the mains supply, the batteries capacity becomes only relevant in case of mains powerfail. From fail on the battery has to deliver all the energy used by the load. The longer an experiment should be continued without mains power the bigger batteries must be used.

Calculate more power failure buffering time than you ever plan to use. The battery will loose capacity during lifetime and the convenient use will increase the number of "load" Instruments.

Oxygraph power-consumption Serie E, F: nominal mains input: 100 - 240 V 47 - 63 Hz maximum mains range: 90 - 264 V inrush-current: depends on the mains power net impedance, at WGT-Labs we measured maximum 45 A for 5µs. With limited current the inrush becomes lower in current but takes more time. We measured 8A for 50 µs. maximum current: At ambient temperature 25 °C with Chamber temperature set to 0° the Oxygraph takes full peltier-power. Additionally the stirrers and the TIP moving will add to a maximum of 110 W and 0,5 A at 50 Hz. normal operation: 25 ° C ambient and 37° C chamber lead to app. -11% peltier-power thus consuming 40 W from mains power. 25 ° C ambient and 5°C chamber lead to ca. -66% peltier-power thus consuming 75 W from mains power.

I use "load" instrument for all electric equipment connected to the UPS.

Even cheap UPS may work properly. Even the most luxury UPS still can cause some complications with certain load-situations.

We can not guarantee functionality of UPS-powering of Oxygraphs. If all the above mentioned criteria are carefully attended to we suppose experimental equipement will serve smoothly.

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-'''Question:'''  Hi Mario, I would like to purchase back-up power supplies.  Our building       power went out the other night 20 minutes after finishing a human biopsy trial!!  While we escaped a disaster this one time, I would hate to think what could happen in the future...these are trials       are obviously expensive and hard to organize.  I see there are       many different types of back-up power supplies available (for       example, here:  http://www.apc.com/products/category.cfm?id=13) Could you let me know what features the UPS (uninterrupted power       supply) should possess?  Voltage, current, etc, etc.  I believe I       know based on the specs of the oxygraphs, but would like to verify first.
+The problem with uninterrupted power supply divides in some sections:
+# UPS functional type
+Online UPS means, that the output-power ist constantly generated from the battery while the battery becomes constantly loaded from
+mains power. This concept ensures uninterrupted output-power even in the moment of mains powerfail.
+Other concepts deliver mainspower and start generation from battery only in case of powerfail. The startup of generation may take some
+(short) time. So the output-power can have dips or other deformations in the moment of powerfail, which could cause the "load" instruments
+to stop working.
+Choose a high-quality UPS with "online"-generation.
+# UPS output voltage:
+The waveform should be sinewave or stepped approximation to sinewave.
+The voltage should meet the Oxy-requirements which are 110 or 230V at 50 or 60 Hz with serie A-D according to the
+setting at the Oxygraph mains input. Serie E and F accept nominal voltages from 100 to 240 V 47 - 63 Hz, due to accepted tolerances
+of +/- 10 % the maximum range covers 90 - 264 V.
+For the waveform of any UPS is only "close" to a sinewave its always a good idea to stay securely within these ranges and not to
+explore the boundaries. The type of "rectangle"-output UPS and most cheap UPS come with the risk of interference with the loads
+electronics.
+# UPS Output maximum current:
+The instruments powered by the UPS draw different currents at startup, at running with full load or in normal operation. The UPS needs
+to limit the current to prevent its internal electronics from damage. This limitation may cause problems with the "load" instruments especially
+at startup when they need to switch on transformers or to load capacitors, thus drawing inrush-currents.
+Therefore an UPS with inrush capability is preferable.
+# UPS Output thermal current:
+The output current will warm up the internal electronics of the UPS, which is designed for a certain maximum of continuous current.
+All "load"-Instruments together may not reach this value during an experiment.
+So the rated UPS output continuous current has to be higher then the sum of continuous current of all connected instruments, including
+Oxygraphs, computers, monitors.
+# UPS power failure buffering time
+The battery of the UPS in normal operation is fully charged by the mains supply, the batteries capacity becomes only relevant in case of
+mains powerfail. From fail on the battery has to deliver all the energy used by the load. The longer an experiment should be continued without
+mains power the bigger batteries must be used.
+Calculate more power failure buffering time than you ever plan to use. The battery will loose capacity during lifetime and the convenient use
+will increase the number of "load" Instruments.
+Oxygraph power-consumption Serie E, F:
+nominal mains input: 100 - 240 V   47 - 63 Hz
+maximum mains range: 90 - 264 V
+inrush-current: depends on the mains power net impedance, at WGT-Labs we measured maximum 45 A for 5µs. With limited current the
+inrush becomes lower in current but takes more time. We measured 8A for 50 µs.
+maximum current: At ambient temperature 25 °C with Chamber temperature set to 0° the Oxygraph takes full peltier-power. Additionally the
+stirrers and the TIP moving will add to a maximum of 110 W and 0,5 A at 50 Hz.
+normal operation:
+° C ambient and 37° C chamber lead to app. -11% peltier-power thus consuming 40 W from mains power.
+° C ambient and 5°C chamber lead to ca. -66% peltier-power thus consuming 75 W from mains power.
+I use "load" instrument for all electric equipment connected to the UPS.
+Even cheap UPS may work properly.
+Even the most luxury UPS still can cause some complications with certain load-situations.
+We can not guarantee functionality of UPS-powering of Oxygraphs.
+If all the above mentioned criteria are carefully attended to we suppose experimental equipement will serve smoothly.
-'''Answer:'''
-Hi Chris, I fear there is not far much more then the specs to go by. I work from  home today so can`t access the serial  number of your O2ks but I think this link  [http://www.oroboros.at/index.php?id=o2k-series_e-features @OROBOROS] should be helpful anyway, because old and new values are compared. Of course the typical power ratings are only useful if you assume that you already reached thermal equilibrium. Some other considerations: * switching time: In our case we use notebooks for computers, so DatLab  will run some time anyway. However, once a O2k is switched off and on  again WITHOUT getting any contradicting instructions from DatLab it will  try to go to a hardware default temperature of 25 °C. Therefore, once  there was an interruption in the power supply it is necessary to  re-connect (new file) with DatLab to the O2k as soon as possible after  the power is back (switched to the alternative source).
-A different approach would be to contact the people who have experiences with power supplies for O2k's on expeditions, starting with Erich himself but a.) Erich is in the Everest Base camp (presumable fighting with the power supply ) right now and b.) I think these are realy rather different questions. [[User:Fasching Mario|Fasching Mario]] 16:53, 20 March 2013 (CET)
-'''
-Addition:'''
-Dear Mario and Chris,
-my apologies, we don't have any experience with UPS systems on  expeditions. Though power stability (and even oscillations thereof) can  be a real drag, as they also influence POS signal stability.
-So far, we have just reconnected as Mario described in the Wiki  after the power came back on. If it's only a short power cut, not too  many data points are lost (depending on the experiment, of course).
-I have heard of UPS systems that connect between power socket and  consumer, they consist of a kind of constantly recharging battery. Once  there is a power cut, the oxygraph would be directly connected to its  battery part without having to switch, so you  wouldn't have to restart and data loss could be excluded.
-I'd go for something like this….
-Cheers
-[[user:Fmark ]]