Hitachi SJ7002 Series Instruction Manual page 191

Overload
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
Restriction
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
39
Opt. Code
attempts to prevent an over-voltage trip on deceleration due to regeneration. It accomplishes
[OLR]
Symbol
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.
Valid for
[1] to [8]
Inputs
OLR Parameter Selection – Two sets of overload restriction parameter settings and values are
available as outlined in the table below.
B021 – B023
Required
(Set 1),
B024 – B026
Settings
(Set 2)
Default Requires
config.
terminal
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.
Overload Restriction
Operation Mode
Overload Restriction
Setting
Deceleration Rate at
Overload Restriction
Note the following:
• If the overload restriction constant (B023 or B026) is set too short, an over-voltage trip
• When an overload restriction occurs during acceleration, the motor will take longer to reach
Symbol Function Name
OLR Overload Restriction
Selection
Function Code
Function
Set 1
B021
B022
B023
during deceleration will occur due to regenerative energy from the motor.
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
Input
State
ON Selects Overload Restriction Set 2,
B024, B025, B026 settings in effect
OFF Selects Overload Restriction Set 1,
B021, B022, B023 settings in effect
Data or Range
Set 2
B024 00
01
02
03
B025 Rated current * 0.5
to rated current * 2
B026 0.1 to 30 seconds
4–29
SJ700 Inverter
2
Description
Description
Disable
Enabled during accel
and constant speed
Enabled during constant
speed
Enabled during accel,
constant speed, and
decel
Current value at which
the restriction begins
Deceleration time when
overload restriction
operates