GE Fuji Electric AF-300ES Instructions Manual page 124

Constant Torque Range: A speed range in which the motor is
capable of delivering a constant torque, subject to motor
thermal characteristics. This essentially is when the inverter/
motor combination is operating at constant volts/Hz.
Constant Voltage Range (AC Drives): The range of motor op-
eration where the drive's output voltage is held constant as
output frequency is varied. This speed range produces
motor performance similar to a DC drive's constant horse-
power range.
Constant Volts per Hertz (V/Hz): This relationship exists in AC
drives where the output voltage is varied directly propor-
tional to frequency. This type of operation is required to
allow the motor to produce constant rated torque as speed
is varied.
Continuous Duty (CONT): A motor that can continue to oper-
ate within the insulation temperature limits after it has
reached normal operating (equilibrium) temperature.
Converter: The process of changing AC to DC. This is ac-
complished through use of a diode rectifier circuit. The term
"converter" may also refer to the process of changing AC
to DC to AC (e.g. adjustable frequency drive). A "frequency
converter" such as that found in an adjustable frequency
drive, consists of a Rectifier, a DC intermediate circuit, an
inverter and a control circuit.
Current Limiting: An electronic method of limiting the maxi-
mum current available to the motor. This is adjustable so
that the motor's maximum current can be controlled. It can
also be preset as a protective device to protect both the
motor and control from extended overloads.
Damping: Damping is the reduction in amplitude on an os-
cillation in the system.
Dead Band: The range of values through which a system
input can be changed without causing a corresponding
change in system output.
Deviation: Difference between an instantaneous value of a
controlled variable and the desired value of the controlled
variable corresponding to the set point. Also called error.
di/dt: The rate of change in current versus a rate of change
in time. Line reactors and isolation transformers can be used
to provide the impedance necessary to reduce the harmful
effects that unlimited current sources can have on phase
controlled rectifiers (SCR).
Diode: A device that passes current in one direction, but
blocks current in the reversed direction.
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Drift: Drift is the deviation from the initial set speed with no
load change over a specific time period. Normally the drive
must be operated for a specified warm-up time at a speci-
fied ambient temperature before drift specifications apply.
Drift is normally caused by random changes in operating
characteristics of various control components.
Drive Controller: (Variable Speed/Frequency Drive) An elec-
tronic device that can control the speed, torque, horsepower
and direction of an AC motor.
dv/dt: The rate of change in voltage versus a rate of change
in time. Specially designed resistor-capacitor networks can
help protect the diodes from excessive dv/dt which can
result from line voltage spikes, line disturbances and circuit
configurations with extreme forward conducting or reverse
blocking requirements.
Dwell: The time spent in one state before moving to the
next. In motion control applications for example, a dwell
time may be programmed to allow time for a tool change or
part clamping operation.
Duty Cycle: The relationship between the operating and rest
times or repeatable operation at different loads.
Eddy Current: Currents induced in motor components from
the movement of magnetic fields. Eddy currents produce
waste heat and are minimized by lamination of the motor
poles and armature.
Efficiency: Ratio of mechanical output to electrical input in-
dicated by a percent. In motors, it is the effectiveness with
which a motor converts electrical energy into mechanical
energy and electrical drives the effectiveness with which
the drive converts electrical power into adjustable frequency
operation at various operating points.
EMF: The initials of 'electromotive force' which is another
term for voltage or potential difference.
Enable: To allow an action or acceptance of data by apply-
ing an appropriate signal to the appropriate input.
Enclosure: Enclosure refers to the housing in which the con-
trol is mounted. Enclosures are available in designs for vari-
ous environmental conditions.
Encoder: An electromechanical transducer that produces a
serial or parallel digital indication of mechanical angle or
displacement. Essentially, an encoder provides high reso-
lution feedback data related to shaft position and is used
with other circuitry to indicate velocity and direction. The
encoder produces discrete electrical pulses during each
increment of shaft rotation.
Error: Difference between the set point signal and the
feedback signal. An error is necessary before a correc-
tion can be made in a controlled system.
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