UPS: Uninterruptible Power Systems

  1. UPS systems are designed to integrate easily into the standard electrical infrastructure, so that means smaller power requirements are typically single-phase designs, with larger power requirements being handled by three-phase systems. In America, the typical single-phase UPS design is smaller than_____KVA , while three-phase systems start around 8KVA and go into the MVAs. In some counties in Europe, all systems greater than 8 kVA must have a three-phase input to make sure the utility mains electrical system stays balanced. PP495 Data Center Handbook: 2015, Hwaiyu Geng. Wiley & Sons Inc
    In America, the typical single-phase UPS design is smaller than 25KVA
  2. IT systems are at risk even in the largest data centers. Of the 450 Fortune 1000 companies surveyed, each site suffered an average of _____ failures each year. About 28% of these incidents were caused by power problems. PP495 Data Center Handbook: 2015, Hwaiyu Geng. Wiley & Sons Inc
    Of the 450 Fortune 1000 companies surveyed, each site suffered an average of 9 of these each year.
  3. ____% of companies that experience a computer disaster and don’t have a survival plan go out of business within 18 months. PP 496 Data Center Handbook: 2015, Hwaiyu Geng. Wiley & Sons Inc
    90% of companies that experience a computer disaster and don’t have this go out of business in 18 months or less.
  4. UPS designs get a base classification by the actual energy storage/delivery method used. There are two general classifications: What are they? PP 496 Data Center Handbook: 2015, Hwaiyu Geng. Wiley & Sons Inc
    static and rotary are the two types of design for these electrical components.
  5. Rotary UPS uses a rotating device (generator) that is typically powered by the utility : through some type of motor system. The rotary generator, sometimes labeled _______, typically a heavyweight flywheel assembly to store energy allows the generator section time to start, and then :>vide power when AC utility power is lost. PP 496 Data Center Handbook: 2015, Hwaiyu Geng. Wiley & Sons Inc
    Diesel Rotary UPS (DRUPS) is this.
  6. Mexico and other parts of Central America use what voltage for their standard single-phase distributed voltage. PP 496 Data Center Handbook: 2015, Hwaiyu Geng. Wiley & Sons Inc
    In this geographic area, they use 127V for their standard single-phase distributed voltage.
  7. UPS for three-phase applications are typically manufactured 120, 220 Y/127, 480 Y277, and 600 Y/______volt for for North America and 380Y/220, 400Y230, and 415Y/240V for the rest of the world. However, some North American data centers are now deploying 415 or 400V products to operate the IT loads close to their maximum value, driving up the efficiency power supplies. I addition, the entire data center benefits as this eliminates the needs for 480 or 600V to transformers, typically gaining another 1-3% of efficiency. PP 496 Data Center Handbook: 2015, Hwaiyu Geng. Wiley & Sons Inc
    347V is the 600y/voltage.
  8. UPS for three-phase applications are always manufactured with wye or delta configurations in North America? PP 496 Data Center Handbook: 2015, Hwaiyu Geng. Wiley & Sons Inc
    These electrical power management systems are always manufactured in a wye configuration in North America, versus a popular Delta supplied configuration in Europe, for the purpose of utility balanced phasing.
  9. Static UPS systems include what? For the DC or backup energy source and creates an AC sign wave for the connected load equipment.
    These systems include an inverter.
  10. In a UPS static inverter, the low-cost system: use power transistors or _____, higher-cost systems typically use devices called _____.PP496 Data Center Handbook: 2015, Hwaiyu Geng. Wiley & Sons Inc
    the low-cost system: use power transistors or MOSFETs, higher-cost systems typically use devices called insulated gate bipolar transistors (IGBT’s)
  11. What is a double conversion three phase UPS and how does it function?
    This is the most common type of UPS above 10kVA (Volt-Ampere). Double Conversion On-Line UPS is the same as the Standby UPS except that the primary power path is the inverter instead of the AC mains. failure of the input AC does not cause activation of the transfer switch, because the input AC is not the primary source, but is rather the backup source. Therefore, during an input AC power failure, on line operation results in no transfer time.  Source: https://www.sweetwater.com/insync/double-conversion-line-ups/
  12. Does the inverter on a Double Conversion three phase UPS prevent a transfer from dropout by design?
    No. The inverter power can also drop out briefly, causing a transfer, if the inverter is subjected to sudden changes in the load, or if the inverter experiences an internal control “glitch”. Contrary to popular belief, Double Conversion On-Line UPS systems do exhibit a transfer time, and in actual installations may transfer as frequently as standby type UPS systems; however on line UPS transfers are not related to AC input power failures as they are in a standby UPS. Source: https://www.sweetwater.com/insync/double-conversion-line-ups/
  13. The input power drawn by the large battery charger in a UPS is what?
    The input power drawn by the large battery charger in a UPS is often non-linear and can interfere with building power wiring.  Because any electrical system with rectified power creates a triple harmonic.
  14. What is an IGBT?
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    The IGBT (Insulated Gate Bipolar Transistor) is a semiconductor device with four alternating layers (P-N-P-N) positive, negative, etc. that are controlled by a metal-oxide-semiconductor (MOS) gate structure without regenerative action.  they can handle very high voltages and switch very very quickly.
  15. advances in high-power IGBTs (Insulated gate bi-polar transistors) allow switching frequencies for inverters typically less than 50 kVA in size to be above the human audible range, therefore reducing operational noise. What is the human audible range? PP 496 Data Center Handbook: 2015, Hwaiyu Geng. Wiley & Sons Inc
    18kHz is this range.
  16. Latest-generation double-conversion systems may use a three level inverter design, which doubles the number of what per phase to allow for lower-voltage rated devices to be used in a series relationship. This helps to raise the efficiency of the inverter by typically 1-3% over two-level inverter designs, therefore reducing the overall cost of operating the UPS. PP 496 Data Center Handbook: 2015, Hwaiyu Geng. Wiley & Sons Inc
    • This doubles the number of IGBTs per phase to allow for lower-voltage rated devices to be used in a series relationship.
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  17. UPS use IGBT transistors in place of what, Allowing the UPS rectifier to be controlled such that its input current is sinusoidal and its input Power Factor near 0.99? Both of these traits allow for easy interface with on-site generators, and they eliminate the large costly “harmonic LC” input filter required for SCR-based designs. PP 496 Data Center Handbook: 2015, Hwaiyu Geng. Wiley & Sons Inc
    These use IGBT transistors in place of SCR’s. They are less costly, have a high .99 PF, and it’s input current is sinusoidal.
  18. most basic and typical for a single ups installation is a stand-alone bypass cabinet, typically called a wraparound” PP 497 Data Center Handbook: 2015, Hwaiyu Geng. Wiley & Sons Inc
  19. The most basic and typical for a single UPS installation Maintenance bypass is a stand-alone bypass cabinet which can be completely removed from the load, typically called a__________. Some UPS systems do come with “an internal” maintenance bypass but you need to discuss the capability of this switch the manufacturer to see how much of the ups is serviceable with only this switch installed. PP 496 Data Center Handbook: 2015, Hwaiyu Geng. Wiley & Sons Inc
    A “wraparound” maintenance bypass switch is the term given for these systems.
  20. The UPS needs to be put in to what prior to the system being put in the maintenance bypass?
    Static Bypass prior to the system being put in the maintenance bypass. Maintenance bypass is usually a wrap around switcheither of rotary or MCB design which allows the UPS to be powered down with the load powered directly from the mains whist maintenance is carried out on the UPS. source: http://www.harlandsimonups.com/reference/faqs/
  21. A UPS in static bypass or manual bypass, the load is being fed by?
    Please note that in static bypass or manual bypass the load is being fed by raw mains power and any loss of power during this mode your load will not be protected.
  22. Batteries used to be sized in Ah, they are now sized in?
    Watts per cell (WPC). source: http://www.harlandsimonups.com/reference/faqs/
  23. What is the only type of UPS that can supply a different frequency than the default frequency?
    • An online UPS is the only type of UPS that can do this.
    • source: http://www.harlandsimonups.com/reference/faqs/
  24. What is the purpose of the DC-to-DC converter? PP 497
    the purpose of the DC-to-DC converter is to provide proper battery charging voltage for systems with either a higher or lower DC link “DC Link”
  25. What is a “DC Link”?
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    • A DC link is a connection which connects a rectifier and an inverter.  These links are found in converter circuits and in VFD circuits.  The AC supply of a specific frequency is converted into DC.  This DC, in turn, is converted into AC voltage.  
    • The DC link is the connection between these two circuits.  The DC link usually has a capacitor known as the DC link Capacitor.  This capacitor is connected in parallel between the positive and the negative conductors.  
    • The DC capacitor helps prevent the transients from the load side from going back to the distributor side.  It also serves to smoothen the pulses in the rectified DC. 
    • Source: http://www.electrotechnik.net/2015/02/what-is-dc-link.html
  26. Static bypass switches are typically found in what type of UPS systems?
    double-conversion UPS systems, some higher powered single-conversion systems, and rotary systems. PP497 Data Center Handbook: 2015, Hwaiyu Geng. Wiley & Sons Inc.
  27. What is the function of the Static Bypass Switch in a UPS?
    The job of this switch in a UPS system is to supply a direct path for the utility mains to connected load equipment. PP497 Data Center Handbook: 2015, Hwaiyu Geng. Wiley & Sons Inc
  28. The job of this switch in a UPS system is to supply a direct path for the utility mains to connected load equipment; however, the mains must be within a certain tolerance range, typically +/- what %.
    +/-10% is the tolerance range for mains connected to this. PP497 Data Center Handbook: 2015, Hwaiyu Geng. Wiley & Sons Inc
  29. Static Bypass Switches; there are usually several reasons why the switch is used. What are they?
    • Maintenance of the UPS
    • To quickly transfer power to the utility source
    • to be the main power path for high-efficiency modes in multimode UPS systems. PP 497 Data Center Handbook: 2015, Hwaiyu Geng. Wiley & Sons Inc
  30. When a static bypass switch is used for maintenance of the system, activating the switch to ensure that the utility and UPS output voltages are synchronized so what can be done?
    A maintenance bypass breaker can be closed. PP 497 Data Center Handbook: 2015, Hwaiyu Geng. Wiley & Sons Inc

    • Static switches are built using SCRs, as they are (1-10ms) to close than mechanical-type contractors (50-100ms). They need to be able to close within milliseconds (ms) to make sure the load equipment does not see a large disruption in what? PP497 Data Center Handbook: 2015, Hwaiyu Geng. Wiley & Sons Inc
    • mains power.
  31. Some UPS designs use both SCRs and a mechanical contractor in parallel, as the SCRs make the quick transition and the contractor closes to provide unlimited bypassing. This type of static bypass is known as what? PP 497 Data Center Handbook: 2015, Hwaiyu Geng. Wiley & Sons Inc.
    A “momentary static switch,” and most times, is NOT rated to operate continuously and if it had to operate under full load, it would fail.
Author
johnbowens
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330958
Card Set
UPS: Uninterruptible Power Systems
Description
Source: Data Center Handbook / edited by Hwaiyu Geng. Copyright © 2015 by John WileY & Sons, Inc. All rights reserved
Updated