Hitachi SJ700-2 instruction manual Overload restriction/overload notice

Related code

b021: Overload restriction operation mode

b022: Overload restriction setting

b023: Deceleration rate at overload restriction

b024: Overload restriction operation mode (2)

b025: Overload restriction setting (2)

b026: Deceleration rate at overload restriction (2)

C001 to C008: Terminal [1] to [8] functions

C021 to C025: Terminal [11] to [15] functions

C026: Alarm relay terminal function

C040: Overload signal output mode

C041: Overload level setting

C111: Overload setting (2)

Chapter 4 Explanation of Functions

4.2.30 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. When you have selected the sensorless vector control, 0Hz-range sensorless vector control, or vector control with sensor as the V/F characteristic curve selection (see Section 4.2.18) and "03" for "b021" or "b024", the inverter output frequency increases if the current over the overload restriction level flows during the regenerative operation.

If the value set as the deceleration rate at overload restriction (b023/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. (See Section 4.2.8.)

-Increase the torque boost setting. (See Section 4.2.19.)

-Increase the overload restriction setting (b022/b025).

Item	Function code	Data or range of data	Description
		00	Disabling the overload restriction
		01	Enabling the overload restriction during
Overload			acceleration and constant-speed operation
		02	Enabling the overload restriction during
restriction	b021/b024		constant-speed operation
operation mode		03	Enabling the overload restriction during
			acceleration and constant-speed operation
			(increasing the frequency during regenerative
			operation)
Overload	b022/b025	"Rated current x 0.5" to	Current at which to trigger the overload restriction
restriction setting		"rated current x 2.0" (A)
Deceleration rate			Deceleration time to be applied when the overload
at overload	b023/b026	0.1 to 30.0 (s)	restriction operates
restriction
Terminal function	C001 to C008	39	Terminal to switch the overload restriction setting

Overload restriction level b022/b025

Deceleration according to the deceleration rate at overload restriction

Output current

Maximum frequency

A004/A204/A304Target frequency F001

Inverter output frequency

b023/b026

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