Hitachi SJ7002 Series Instruction Manual page 38

1–16
Introduction to Variable-Frequency Drives
Intelligent
Functions and
Parameters
Braking
Velocity Profiles
Much of this manual is devoted to describing how
to use inverter functions and how to configure
inverter parameters. The inverter is microproces-
sor-controlled, and has many independent
functions. The microprocessor has an on-board
EEPROM for parameter storage. The inverter's
front panel keypad provides access to all
functions and parameters, which you can access
through other devices as well. The general name
for all these devices is the digital operator, or
digital operator panel. Chapter 2 will show you
how to get a motor running, using a minimal set
of function commands or configuring parameters.
The optional read/write programmer will let you
read and write inverter EEPROM contents from
the programmer. This feature is particularly
useful for OEMs who need to duplicate a particu-
lar inverter's settings in many other inverters in
assembly-line fashion.
In general, braking is a force that attempts to slow or stop motor rotation. So it is associated
with motor deceleration, but may also occur even when the load attempts to drive the motor
faster than the desired speed (overhauling). If you need the motor and load to decelerate
quicker than their natural deceleration during coasting, we recommend installing a braking
resistor. The dynamic braking unit (built into certain SJ700
energy into a resistor to slow the motor and load (see
"Dynamic Braking" on page 5–6
the motor for extended periods of time, the SJ700
distributor).
The inverter parameters include acceleration and deceleration, which you can set to match the
needs of the application. For a particular inverter, motor, and load, there will be a range of
practically achievable accelerations and decelerations.
The SJ700 inverter is capable of sophisti-
2
cated speed control. A graphical representa-
tion 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, the acceler-
ation is a ramp to a set speed, and the decel-
eration is a decline to a stop.
models) sends excess motor
2
"Introduction" on page 5–2
for more information). For loads that continuously overhaul
may not be suitable (contact your Hitachi
2
Speed
and
Fixed speed
Accel Decel
t
Velocity Profile