Hitachi L300P Series Instruction Manual page 166

4–32
Using Intelligent Input Terminals
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 Code
Function
Set 1
Overload Restriction B021
Operation Mode
Overload Restriction B022
Setting
Deceleration Rate at B023
Overload Restriction
Opt.
Symbol Function Name
Code
39 OLR Overload Restric-
tion Selection
C001, C002, C003, C004,
Valid for inputs:
C005
B021, B022, B023 (Mode 1),
Required
B024, B025, B026 (Mode 2)
settings:
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
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
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
Example: (Requires input configuration—
see page 3–43. Jumper position shown is
for –xFU/-xFR models; for –xFE models,
see page 4–11.)
TH FW
P24 PLC
See I/O specs on page 4–8.
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
Description
OLR
5 4 3 2 1
CM1