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ON
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Fusible
2.46 ABB Control Inc.
AC 1700 – 5/00
Definitions
F
Definitions
AC – Alternating current — Current that reverses its direction
of flow twice per cycle.
Ambient temperature — Temperature of the air surrounding
the unit.
Amp rating — The basic unit of measurement for electric
current (columbs / seconds).
Conventional thermal current Ith — Value of the current the
disconnect switch can withstand with poles in closed position,
in free air for an eight hour duty, without the temperature rise of
its various parts exceeding the limits specified by the
standards.
Cycle duration — Total time of the on-load + off-load period.
DC – Direct current — Current that flows in only one direction.
Electrical endurance — Number of on-load operating cycles.
IEC environmental protection type — see page 1.59.
Full load amp current FLA — The current required by a motor
to produce full-load torque at the motor's rated speed.
Inductive load — An electrical load characterized by having
significant inrush (5 to 6 times FLA for typical design-B AC
induction motors).
kW — Kilowatts (1000 watts)
Lockout/Tagout — Means of removing power from electrical
equipment during inspection, service or repair.
Make / Break — ON / OFF
Mechanical endurance — Number of off-load operating
cycles.
Poles in series — Means of connection poles using wires or
bus bars to increase breaking capacity of load.
Power factor — The relationship between working power and
total power consumed. Power factor measures how effectively
electrical power is being used.
Rated insulation Ui — Voltage value which designates the
unit and to which dielectric tests, clearance and creepage
distances are referred.
Rated operating current Ie — Current value stated by the
manufacturer and taking into account the rated operating
voltage Ue, the rated frequency, the rated duty, the utilization
category, the electrical contact life and the type of protective
enclosure.
Rated operating voltage Ue — Voltage value to which
utilization characteristics of the disconnect switch are referred,
i.e. phase-to-phase voltage in 3 phase circuits.
Rated short circuit making capacity Icm — The rated short-
circuit making capacity of a disconnect switch, a disconnector
or a switch-disconnector is the value assigned to equipment at
the rated operational voltage, frequency (if any) and specified
power-factor for AC or time constant for DC. It is expressed as
the maximum prospective peak current under prescribed
conditions.
Rated short time withstand current Icw — The rated short-
time withstand current of a disconnect switch, a disconnector
or a switch-disconnector is the value that the equipment can
carry without damage, under the test conditions specified in the
relevant product standard. The value of the rated short-time
withstand current shall be not less than twelve times the
maximum rated operational current unless otherwise stated by
manufacturer and the duration of the current shall be 1 s.
Resistive load — An electrical load characterized by not
having any significant inrush current.
Short circuit protection co-ordination — Co-ordination types
"1" and "2" are defined in IEC 947-4-1.
Type 1 co-ordination — There has to be no discharge of
parts beyond the enclosure. Damage to the contactor and
the overload is acceptable.
Type 2 co-ordination — No damage to the overload relay or
other parts has occured, except that welding of contactor or
starter contacts is permitted, if they are easily separated.
Time constant — Ratio of inductance to the resistance: L/R =
mH/Ohm = ms.
Torque — The force that produces rotation. It is commonly
measured in pound-feet (lb-ft). Torque applies to such things
as motor operations, handle rotations, wire tightening.
UL environmental protection type — see page 1.58.
Volt — The unit of electrical potential difference and
electromotive force.