Hitachi SJ300 Series, Instruction Manual

Page: 173 / 294

SJ300 Inverter
Oper
ati
ons
and Monitor
ing
4–35
Overload
Restriction
The inverter constantly monitors the motor current during acceleration, deceleration, and
constant speed. If the inverter reaches the overload restriction level, it adjusts the output
frequency automatically to limit the amount of overload. This function prevents an over-current
trip by inertia during rapid acceleration or large changes in load at constant speed. It also
attempts to prevent an over-voltage trip on deceleration due to regeneration. It accomplishes
this by temporarily suspending deceleration and/or increasing the frequency in order to dissi-
pate regenerative energy. Once the DC bus voltage falls sufficiently, deceleration will resume.
OLR Parameter Selection – Two sets of overload restriction parameter settings and values are
available as outlined in the table below. Use the B021—B026 group of settings to configure the
two set of parameters as needed. By assigning the Overload Restriction function [OLR] to an
intelligent terminal, you can select the set of restriction parameters that is in effect.
Function
Function Code
Data or Range Description
Set 1 Set 2
Overload Restriction
Operation Mode B021 B024 00 Disable
01 Enabled during accel
and constant speed
02 Enabled during constant
speed
03 Enabled during accel,
constant speed, and
decel
Overload Restriction
Setting B022 B025 Rated current * 0.5
to rated current * 2 Current value at which
the restriction begins
Deceleration Rate at
Overload Restriction B023 B026 0.1 to 30 seconds Deceleration time when
overload restriction
operates
Opt.
Code
Symbol Function Name
Input
State
Description
39 OLR Overload Restric-
tion Selection ON Selects Overload Restriction Set 2,
B024, B025, B026 settings in effect
OFF Selects Overload Restriction Set 1,
B021, B022, B023 settings in effect
Valid for inputs:
C001, C002, C003, C004,
C005, C006, C007, C008
Required
settings:
B021, B022, B023 (Mode 1),
B024, B025, B026 (Mode 2)
Notes:
•
If the overload restriction constant (B023 or
B026) is set too short, an over-voltage trip
during deceleration will occur due to regener-
ative energy from the motor.
• When an overload restriction occurs during
acceleration, the motor will take longer to
reach the target frequency, or may not reach
it. The inverter will make the following
adjustments:
a) Increase the acceleration time
b) Raise torque boost
c) Raise overload restriction level
5 3 1
7 6 4 2
8
FW TH
PLC
CM1
P24 CM1
See I/O specs on page 4–9 .
Example: (Requires input configuration—
see page
3–47 . Jumper position shown is
for –xFU/-xFR models; for –xFE models,
see page
4–12 .)
OLR