Power Management How well do you know UPS systems?
Take our short 10 question true/false quiz to see where you stand!
(Or skip to the answers below).
1. The only purpose of the UPS is to minimize data loss from unexpected loss of power.
2. I can assume that power factor is 1 when I spec out my UPS. So I can use either VA or Watts.
3. The health of my battery depends on their temperature.
4. I don’t need a maintenance bypass switch for the UPS.
5. My UPS batteries are only good for 3 + years.
6. All UPS units are scalable.
7. Redundant UPS systems have no single points of failure.
8. Batteries are the most likely component to fail in a UPS.
9. All UPS systems have dual inputs.
10. Feeding your existing single-phase UPS system with a single large 3-phase UPS system (in series) increases reliability.
| 1. TRUE OR FALSE? THE ONLY PURPOSE OF THE UPS IS TO MINIMIZE DATA LOSS FROM UNEXPECTED LOSS OF POWER. |
| FALSE |
| While the primary purpose for a UPS is to minimize data loss from an unexpected loss of power, there are many power-related issues that can be averted by using a UPS. At the most basic levels, virtually all UPS units will provide some level of surge protection. This provides protection from unrecoverable equipment failure. This type of protection can also be accomplished from most power strips. |
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| This diagram details some of the events that a UPS may be able to handle. As shown, sags and surges are actually more common than complete outages. Further, most enterprise-class UPS units also provide power conditioning. The power coming from the utility is not always a perfect sine wave. There are unexpected sags and spikes in voltage that adversely affect the connected equipment. While these events may not cause a loss of data or loss of service, they can stress the sensitive components in a computer (mainly the power supply) which can cause premature failure. This type of protection can generally only be achieved by a UPS type device and not a power strip; the mechanism by which it works would require an additional source of backup power. |
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| This is the schematic for a simple standby UPS. This device includes a filter and surge suppression between the load and the utility power. However, the load is normally powered by the utility power and thus the filter is the primary source of protection. This type of device cannot scale up and the switching time for the transfer switch technically introduces a small (usually negligible) interruption of power. |
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| Above is a diagram of a double-conversion UPS. Its load (AC Output) is always powered directly through the inverter (rectifier/charger). Thus, the power should always be a controlled and consistent digital sine wave. This virtually eliminates any noise or spikes in the line. |
| 2. TRUE OR FALSE? I CAN ASSUME THAT POWER FACTOR IS 1 WHEN I SPEC OUT MY UPS. SO I CAN USE EITHER VA OR WATTS. |
| FALSE |
| Power factor typically ranges from about 0.7 to 1.0 (unity). The advertised VA ratings will need to be converted to Watts using the output pf of the unit. Many UPS manufacturers will also provide the load Watt ratings which allow for easier planning of UPS capacity. |
| 3. TRUE OR FALSE? THE HEALTH OF MY BATTERY DEPENDS ON THEIR TEMPERATURE. |
| TRUE |
| Batteries use chemical reactions to supply electrons (and thus electricity) to a circuit. As with all chemical reactions, change in temperature will affect the battery’s properties. Higher temperatures can cause undesirable affects in the way that a battery’s cathode and anode react. Amongst other things, the internal resistance increase at a higher rate and the cathodes and anodes will become less efficient more quickly (these processes will happen to all batteries with time and use). This has the negative effect of shorter battery service life and even potential hazards. |
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| According to the chart above, a battery can increase its internal resistance by as much as 30% within 6 months of usage at 55deg C (131 deg F). Conversely, temperatures below normal room temperature (about 20 deg C) can have adverse effects on battery discharge times and standby times. The best ambient temperatures for batteries is at about 78 deg F (25.5 deg C) to keep the battery discharging at a proper rate and also keep service life an optimal interval. |
| 4. TRUE OF FALSE? I DON’T NEED A MAINTENANCE BYPASS SWITCH FOR THE UPS. |
| FALSE |
| A maintenance bypass switch allows for general UPS maintenance without having to disconnect the equipment power. As UPS units will require regular maintenance, the lack of a bypass switch will guarantee that your equipment will have to be powered off at least once every few years. So while a bypass switch is not required, planned or unplanned maintenance will require a shutdown of the downstream load. |
| 5. TRUE OR FALSE? MY UPS BATTERIES ARE ONLY GOOD FOR 3 + YEARS. |
| FALSE |
There are many variables that affect battery life. These can include battery type, UPS type, discharge frequency and environmental factors. The best way to accurately gauge battery life is to properly maintain the UPS and battery. UPS units have self tests and maintenance routines built-in that can be run to accurately measure battery life and health. The best recommendation for battery service interval is to use historical data, maintenance, and self-test on the device. Always use the manufacturer’s recommended service and replacement intervals when applicable. |
| 6. TRUE OR FALSE? ALL UPS UNITS ARE SCALABLE. |
| FALSE |
There are multitudes of options in terms of scalable UPS systems. There are also many UPS units on the market that have a fixed kVA rating with no option of upgrading. Thus, proper capacity planning is very important in determining UPS selection as the cost of replacing a fixed unit might greatly eliminate any initial cost savings. Some scalable types of UPS units are firmware upgradeable which require a technician to come and upgrade the firmware. This allows for a higher VA rating without any device modification. These units are the easiest upgrade path since they don’t require any new hardware. As an example, some units can go from 40kVA to 60kVA and to 80kVA all on the same chassis. |
| 7. TRUE OR FALSE? REDUNDANT UPS SYSTEMS HAVE NO SINGLE POINTS OF FAILURE. |
| FALSE |
| Virtually all systems have a single point of failure. Primarily, a redundant system must be able to switch from the active UPS system to the standby system. This is facilitated by some type of transfer switch which is a single point of failure. It is not impossible to build a truly redundant system with no single points of failure. However, this would involve two power feeds from separate utilities, devices which support dual power inputs, and a mirror copy of all infrastructure including UPS, PDUs, and electrical panels. |
| 8. TRUE OR FALSE? BATTERIES ARE THE MOST LIKELY COMPONENT TO FAIL IN A UPS. |
| TRUE |
| Batteries are the most likely component to fail in a UPS system. This risk can be minimized by proper service, monitoring, redundant battery system, and also through substitute energy storage technology such as a flywheel. |
| 9. TRUE OR FALSE? ALL UPS SYSTEMS HAVE DUAL INPUTS. |
| FALSE |
| Not all UPS systems have dual inputs. However, they are an important component of a UPS. They allow for the bypass switch to have its own input which allow for an independent breaker from the rectifier input of the UPS. This eliminates the potential for complete system shutdown if the circuit feeding the UPS is tripped. |
| 10. TRUE OR FALSE? FEEDING YOUR EXISTING SINGLE-PHASE UPS SYSTEM WITH A SINGLE LARGE 3-PHASE UPS SYSTEM (IN SERIES) INCREASES RELIABILITY. |
| FALSE |
| Ignoring the fact that there would be reduced efficiency running through two UPS systems in series, single-phase units are generally less reliable and would decrease the overall system reliability. A much better method would be to run UPS systems in parallel which requires that downstream devices have dual power inputs. |
If you are:
- experiencing challenges with your UPS system
- would like to increase your UPS system's availability, reliability, efficiency
- are in the market for a new UPS system and would like recommendations
