Hitachi SJ100 Instruction Manual page 41

1–22
Introduction to Variable-Frequency Drives
Velocity Profiles
The SJ100 inverter is capable of sophisticated
speed control. A graphical representation of
that capability will help you understand and
configure the associated parameters. This
manual makes use of the velocity profile
graph used in industry (shown at right). In the
example, acceleration is a ramp to a set speed,
and deceleration is a decline to a stop.
Acceleration and deceleration settings specify
the time required to go from a stop to
maximum frequency (or visa versa). The
resulting slope (speed change divided by time)
is the acceleration or deceleration. An increase
in output frequency uses the acceleration
slope, while a decrease uses the deceleration
slope. The accel or decel time a particular
speed change depends on the starting and
ending frequencies. However, the slope is constant, corresponding to the full-scale accel
or decel time setting. For example, the full-scale acceleration setting (time) may be 10
seconds—the time required to go from 0 to 60 Hz.
The SJ100 inverter can store up to 16 preset
speeds. And, it can apply separate acceleration
and deceleration transitions from any preset to
any other preset speed. A multi-speed profile
(shown at right) uses two or more preset
speeds, which you can select via intelligent
input terminals. This external control can
apply any preset speed at any time. Alterna-
tively, the selected speed is infinitely variable across the speed range. You can use the
potentiometer control on the keypad for manual control. The drive accepts analog 0-10V
signals and 4-20 mA control signals as well.
The inverter can drive the motor in either
direction. Separate FW and RV commands
select the direction of rotation. The motion
profile example shows a forward motion
followed by a reverse motion of shorter
duration. The speed presets and analog signals
control the magnitude of the speed, while the
FWD and REV commands determine the
direction before the motion starts.
NOTE: The SJ100 can move loads in both directions. However, it is not designed for use
in servo-type applications that use a bipolar velocity signal that determines direction.
Set speed
Speed
Accel
0
Velocity Profile
Speed
Maximum speed
0
Acceleration
(time setting)
Speed
Speed 2
Speed 1
0
Multi-speed Profile
Speed
Forward move
0
Bi-directional Profile
Decel
t
t
t
t
Reverse move