Hitachi SJ100 Series Instruction Manual page 6

Momentum
Multi-speed Operation
Motor Load
NEC
NEMA
Power Factor
PID Loop
Process Variable
PWM
Reactance
The physical property of a body in motion that causes it to continue
to move in a straight line. In the case of motors, the armature and
shaft are rotating and possesses angular momentum.
The ability of a motor drive to store preset discrete speed levels for
the motor, and control motor speed according to the currently
selected speed preset. The Hitachi inverters have 16 preset speeds.
In motor terminology, motor load consists of the inertia of the
physical mass that is moved by the motor and the related friction
from guiding mechanisms. See also inertia.
The National Electric Code is a regulatory document that governs
electrical power and device wiring and installation in the United
States.
The National Electric Manufacturer's Association. NEMA Codes
are a published series of device ratings standards. Industry uses
these to evaluate or compare the performance of devices made by
various manufacturers to a known standard.
A ratio that expresses a phase difference (timing offset) between
current and voltage supplied by a power source to a load. A perfect
power factor = 1.0 (no phase offset). Power factors less than one
cause some energy loss in power transmission wiring (source to
load).
Proportional - Integral-Derivative - a mathematical model used for
process control. A process controller maintains a process variable
(PV) at a setpoint (SP) by using its PID algorithm to compensate for
dynamic conditions and vary its output to drive the PV toward the
desired value. For variable-frequency drives, the process variable is
the motor speed. See also error.
A physical property of a process which is of interest because it
affects the quality of the primary task accomplished by the process.
For an industrial oven, temperature is the process variable. See also
PID Loop and error.
Pulse-width modulation: A type of AC adjustable frequency drive
that accomplishes frequency and voltage control at the output
section(inverter) of the drive. The drive output voltage waveform is
at a constant amplitude, and by "chopping" the waveform (pulse-
width-modulating), the average voltage is controlled. The chopping
frequency is sometimes called the carrier frequency.
The impedance of inductors and capacitors has two components.
The resistive part is constant, while the reactive part changes with
applied frequency. These devices have a complex impedance
(complex number), where the resistance is the real part and the
reactance is the imaginary part.
A–5
SJ100 Inverter