Overload Restriction/Overload Notice (B021 To B026,C001 To C005,C021,C026,C040,C041) - Hitachi NES1-004SB Quick Reference Manual

7.8.3 Overload restriction/overload notice
(1) Overload restriction function
- The overload restriction function allows you to make the inverter monitor the motor current during
acceleration or constant-speed operation and automatically reduce the output frequency according to the
deceleration rate at overload restriction when the motor current reaches the overload restriction level.
- This function prevents the moment of inertia from excessively increasing during motor acceleration and
prevents the inverter from tripping because of overcurrent, even when the load changes suddenly during
the constant-speed operation of the motor.
- You can specify two types of overload restriction operation by setting functional items "b021", "b022", and
"b023" and functional items "b024", "b025", and "b026" separately.
- To switch the overload restriction operation between the two settings (setting with b021, b022, and b023
and setting with b024, b025, and b026), assign function "39" (OLR) to an intelligent input terminal. Turn the
- OLR signal on and off to switch between the two settings.
- The overload restriction level specifies the current at which to trigger the overload restriction function.
- The deceleration rate at overload restriction specifies the length of time to decelerate the motor from the
maximum frequency to 0 Hz.
-When this function operates during deceleration,the acceleration time is prolonged over the set time.
If the value set as the deceleration rate at overload restriction (b023/b223/b026) is too small, the inverter
automatically decelerates the motor even during acceleration because of the overload restriction, and may
trip because of the overvoltage caused by the energy regenerated by the motor.
If this function operates during acceleration and the output frequency cannot reach the target frequency,
try to make the following adjustments:
- Increase the acceleration time.
- Increase the overload restriction setting (b022/b222/b025).
Item Function code
Overload
b021/b221
restriction
operation mode
Overload b022/b222
restriction setting
Deceleration rate
b023/b223
at overload
restriction
Terminal function C001 to C005
Overload restriction level
b022/b222/b025
Output current
Maximum frequency
A004/A204
Inverter output
frequency
Data or range of data
00
01
b024
02
"Rated current x 0.2" to
b025 "rated current x 2.0" (A)
0.1 to 3000. (s)
b026
39
b023/b223/b026
Chapter 7 Explanation of Functions
Disabling the overload restriction
Enabling the overload restriction during
acceleration and constant-speed operation
Enabling the overload restriction during
constant-speed operation
Current at which to trigger the overload restriction
Deceleration time to be applied when the overload
restriction operates
Terminal to switch the overload restriction setting
Deceleration according to the
deceleration rate at overload
restriction
7 - 63
Description
Target frequency
F001