3.3.10. Uninterruptible Power Supply - UPS

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Pulse rectifier (SPS - Switching Power Supply) computers can somewhat mitigate voltage instability metropolitan network, but in terms of a power outage or severe power surges - 'syringe' is of no use. In the event of a power line voltage off the computer because its adapter no possibility of accumulation of energy and inevitably leads to loss of current information in working memory, or worse can damage the tracks on the disk drive if the recess formed in the moment of reading or writing disk. No idyllic scenario for one server.

To safeguard the validity of the computer, and thus the data stored on the disks when working with a computer, it is useful to connect to a computer via the source uninterruptible power supply - UPS (Uninterruptable Power Supply). In the event of a power failure using internal battery ensures your computer, the line voltage for a few minutes to a few tens of minutes, depending on the consumption of a computer system and the battery capacity, which is enough to store data and shut down in the meantime, there is no establishment of the line voltage.

UPS I realized as switching (off-line) which reacts exclusively by a power failure when in a few thousandths of a second generation of electronics over network voltage conversion of battery voltage or a constant (on-line) that continuously performs conversion of battery voltage to AC voltage and the battery are constantly being updated. Of course, the other species exposed to continuous stress and therefore larger and heavier and more expensive. Good properties have UPS devices like 'off-line' holding voltage stabilizer (AVR - Automatic Voltage Regulator) which reduces the line voltage fluctuation, even in the range of 150 V-300 V (European standard). For UPS is important and the time needed to 'understand' disappearance of the line voltage and generating power from its own DC/AC (direct current / alternate current) converters, and response time (response time / switching time) if power voltage is good that the 'off-line' device is less than 5 ms. Importance forms generated output voltage is also of importance, and it may be a rectangular shape, or some variant of the closest form of sinusoidal or sinusoidal form, which of course raises the price of the device.

 UPS device  
Figure 3.3.40 UPS device.    

No matter what type of UPS is selected, it is good to opt for one that has a 25%-50% greater opportunities for effective power control and the burden is not advisable to use consumers who have inductive properties. What is the battery capacity greater autonomy for individual work is higher, which is useful for servers that are essentially the day without physical inspection. If the line voltage fluctuates too much attention should be paid to the range of fluctuations in line voltage that the UPS can cancel Then this particular character is more important than the capacity of the battery installed. The purpose of the decision when purchasing the device shall first determine what are the common phenomenon on the power supply line that is used to connect the computer. Better UPS devices (usually branded SMART) have a serial port (COM) or USB port for connection to a computer, which along with related program support monitors the condition Consuming batteries if power fails. When the battery voltage reaches below a critical threshold, the UPS signals that the computer automatically shuts down, and then automatically UPS is turned off. Understandable optical and acoustic signaling UPS is not superfluous.


Example XVI

Principle of working UPS 'off-line' type.

 Block diagram of UPS
Figure 3.3.41 Block diagram of action UPS 'off-line' type.

In the presence of the line voltage switch 'P' stands in the position of '1', and the battery is charging power through an AC adapter. In the event of a power line voltage, the control electronics for a few thousandths of a second facility electrical power failure and switches the switch to position '2' and uses AC voltage 220 V (Europe) obtained from the inverter battery voltage. By establishing the line voltage control electronics switches switch 'P' in position '1'. The stabilizer is a circuit that not all UPS devices. Has the task to automatically adjust the line voltage at the rated value of 220 V in the case of deviations to less or greater value than the standard, which uses auto transformer (line-interactive UPS). The filter has a duty to mitigate distortion forms the output voltage, which is the value of 25-30% reduces the value of approximately 5-10% (liabilities PFC). If on the other hand uses an advanced electronic system that acts as an active filter (Active PFC) distortion is about 5% at any load. In doing so, the vectors of current and voltage phase trying to get closer to reactive power can be limited. Using IGBT (insulated gate bipolar transistor) technology distortion can be reduced by up to 2%.

UPS type 'on-line' no branch that leads to the switch position '1 'and continuously performs correction and conversion of electrical energy (double-conversion). The advantage is that consumers are then continuously separated from the line voltage, which contributes to the security and stability of the system. Certainly PFC system is implied.

So, according to the form of the output voltage if power system voltage UPS is made with the converter as a generator of sinusoidal output voltage or rectangular shapes. Sine wave generator is more useful because it enables the connection of inductive loads, but its price is higher. For the server is certainly good to choose exactly this type of UPS, and opportunities to Croatia to choose such an energy capacity of the battery to ensure the autonomy of the system for at least 12 hours.

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