Powerware Power Protection Handbook for IBM 9910 International System i and System p Applications
8
Glossary of Power Terms
Ampere (A or Amp)
– The unit of measure for the “rate of
flow” of electricity, analogous to “gallons per minute.”
VA x 0.7 (power factor) = Watts
Alternating Current (AC)
– An electric current that reverses
its direction at regularly recurring intervals.
Arc
– Sparking that results when undesirable current flows
between two points of differing potential. This may be due to
leakage through the intermediate insulation or a leakage path
due to contamination.
Audible Noise
– A measure of the noise emanating from a
device at audible frequencies.
Backup Time
– The amount of time the battery in a UPS is
designed to support the load.
Blackout
– A zero-voltage condition lasting for more than two
cycles.
BTU
– British Thermal Unit. Used to measure heat dissipation.
Energy required to raise one pound of water one degree
Fahrenheit. One pound of water at 32 degrees F requires the
transfer of 144 BTUs to freeze into solid ice.
Brownout
– A steady state of low voltage, but not zero
voltage.
Common Mode Noise
– An undesirable voltage that appears
between the power conductors and ground.
Crest Factor
– Usually refers to current. It is the mathematical
relationship between RMS current and peak current. A normal
resistive load will have a crest factor of 1.4142, which is the
normal relationship between peak and RMS current. A typical
PC will have a crest factor of 3.
Critical Equipment
– Equipment such as computers,
communications systems or electronic process controls, whose
continuous availability is imperative.
Direct Current (DC)
– An electric current in which the flow of
electrons is in one direction, such as supplied by a battery.
Double-Conversion
– A UPS design in which the primary
power path consists of a rectifier and inverter. Double con-
version isolates the output power from all input anomalies such
as low voltage surges and frequency variations.
Downtime
– The time during which a functional unit cannot be
used because of a fault within the functional unit or within the
environment.
Electrical Line Noise
– Radio frequency interference (RFI),
electromagnetic interference (EMI) and other voltage or
frequency disturbances.
Electromagnetic Interference (EMI)
– Electrical interference
that can cause equipment to work improperly. EMI can be
separated into conducted EMI (interference conducted through
cables out of the UPS) and radiated EMI (interference
conducted through the air).
Ground
– A conducting connection, whether intentional or
accidental, by which an electric circuit or equipment is
connected to the earth, or to some conducting body of
relatively large extent that serves in place of the earth.
Harmonic
– A sinusoidal component of an AC voltage that is
multiple of the fundamental waveform frequency. Certain
harmonic patterns may cause equipment problems.
Harmonic Distortion
– Regularly appearing distortion of the
sine wave whose frequency is a multiple of the fundamental
frequency. Converts the normal sine wave into a complex
waveform.
Hertz (Hz)
– A unit of frequency equal to one cycle per second.
High Voltage Spike
– Rapid voltage peak up to 6,000 volts.
Hot-Swappable
– The ability to change a module without
taking the critical load off the UPS.
i5 Server
– The most current generation of the IBM System i™
family of general-purpose systems that supports the i5/OS™
Operating System/400, AIX®, and Linux® operating systems
and that provides application portability across all models.
Input Voltage Range
– The voltage range within which a UPS
operates in “normal” mode and does not require battery power.
Inverter
– UPS assembly that converts internal DC power to
output AC power to run user’s equipment. When the inverter is
supporting 100% of the load at all times, as with an online
UPS, there is no break from utility power to battery power.
Kilovolt Ampere (kVA)
– An approximation of available power
in an AC system that does not take the power factor into
account.
Line-Interactive
– An offline UPS topology in which the
system interacts with the utility line in order to regulate the
power to the load.
Load
– The equipment connected to and protected by a UPS.
Logical Partition (LPAR)
– (1) A set of key or RID pairs in a
non-partitioning index that are associated with a particular
partition. (2) A subset of a single system that contain resources
(processors, memory, and input/output devices). A logical
partition operates as an independent system. If hardware
requirements are met, multiple logical partitions can exist
within a system.
