Frequently Asked Questions - Hitachi SJ100 Instruction Manual

Frequently Asked Questions

Q. What is the main advantage in using an inverter to drive a motor, compared to
alternative solutions?
A. An inverter can vary the motor speed with very little loss of efficiency, unlike
mechanical or hydraulic speed control solutions. The resulting energy
savings usually pays for the inverter in a relatively short time.
Q. The term "inverter" is a little confusing, since we also use "drive" and "amplifier"
to describe the electronic unit that controls a motor. What does "inverter" mean?
A. The terms inverter, drive, and amplifier are used somewhat interchangeably
in industry. Nowadays, the terms drive, variable-frequency drive, variable-
speed drive, and inverter are generally used to describe electronic, micropro-
cessor-based motor speed controllers. In the past, variable-speed drive also
referred to various mechanical means to vary speed. Amplifier is a term
almost exclusively used to describe drives for servo or stepper motors.
Q. Although the SJ100 inverter is a variable speed drive, can I use it in a fixed-speed
application?
A. Yes, sometimes an inverter can be used simply as a "soft-start" device,
providing controlled acceleration and deceleration to a fixed speed. Other
functions of the SJ100 may be useful in such applications, as well. However,
using a variable speed drive can benefit many types of industrial and
commercial motor applications, by providing controlled acceleration and
deceleration, high torque at low speeds, and energy savings over alternative
solutions.
Q. Can I use an inverter and AC induction motor in a positioning application?
A. That depends on the required precision, and the slowest speed the motor will
must turn and still deliver torque. The SJ100 inverter will deliver full torque
while turning the motor at only 0.5 Hz (15 RPM). DO NOT use an inverter if
you need the motor to stop and hold the load position without the aid of a
mechanical brake (use a servo or stepper motion control system).
Q. Does the optional digital operator interface or the PC software (DOP Professional)
provide features beyond what is available from the keypad on the unit?
A. Yes. However, note first that the same set of parameters and functions are
equally accessible from either the unit's keypad or from remote devices. The
DOP Professional PC software lets you save or load inverter configurations
to or from a disk file. And, the hand-held digital operator provides hard-
wired terminals, a safety requirement for some installations.
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SJ100 Inverter