Date Code 20080918 Instruction Manual SEL-749M Relay
Glossary
Instructi on Manual
A
Abbreviation for amps or amperes; units of electrical current magnitude.
ACSELERATOR
®
SEL-5030
A Windows
®
-based program that simplifies settings and provides analysis
support.
Ambient Temperature
Temperature of the motor cooling air at the cooling air inlet. Measured by an
RTD whose location setting is AMB.
ANSI Standard
Device Numbers
A list of standard numbers used to represent electrical protection and control
relays. The standard device numbers used in this instruction manual include:
27 Undervoltage Element
37 Underpower Element
46 Phase Balance or
Current Unbalance Element
47 Phase Sequence Element
49 Thermal Element
50 Overcurrent Element
52 AC Circuit Breaker
55 Power Factor Element
59 Overvoltage Element
66 Jogging Device (limits number of operations within a given time of
each other)
81 Frequency Element
These numbers are frequently used within a suffix letter to further designate
application. The suffix letters used in this instruction manual include:
P Phase Element
G Residual/Ground Element
N Neutral/Ground Element
Q Negative-Sequence (3I2) Element
Antibackspin Protection
Relay function that prevents the motor from being started for a short time after
it is stopped. Used on pump motors to prevent a start attempt while fluid is
running backward through the pump.
Antijogging Protection
Relay functions that prevent the motor from being started too many times
within an hour (also referred to as Starts Per Hour protection) or too soon fol-
lowing the last start (also referred to as Minimum Time Between Starts protec-
tion).
Apparent Power, S
Complex power expressed in units of volt-amps (VA), kilovolt-amps (kVA), or
megavolt-amps (MVA). Accounts for both real (P) and reactive (Q) power
dissipated in a circuit: S = P + jQ.
ASCII
Abbreviation for American Standard Code for Information Interchange.
Defines a standard way to communicate text characters between two elec-
Courtesy of NationalSwitchgear.com
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