Hitachi SJ700-2 instruction manual Free-run stop FRS function

Related code

b088: Restart mode after FRS

b003: Retry wait time before motor restart

b007: Restart frequency threshold

b028: Active frequency matching, scan start frequency

b029: Active frequency matching, scan-time constant

b030: Active frequency matching, restart frequency select

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

Chapter 4 Explanation of Functions

4.2.47 Free-run stop (FRS) function

The free-run stop (FRS) function allows you to shut off the inverter output to let the motor start free-running.

You can effectively use this function when stopping the motor with a mechanical brake (e.g., electromagnetic brake). If an attempt is made to forcibly stop the motor with a mechanical brake while the inverter keeps its output, the inverter may trip because of overcurrent.

To use this function, assign function "11" (FRS) to one of the terminal [1] to [8] functions (C001 to C008). The free-run stop (FRS) function operates as long as the FRS terminal is on. When the FRS terminal is turned off, the inverter restarts the motor after the retry wait time (b003). However, the inverter does not restart the motor if the digital operator (02) has been specified for the run command source setting (A002). To restart the motor in such status, enter a new operation command.

You can select the inverter output mode for restarting with the restart mode after FRS (b088) from starting the motor with 0 Hz, starting the motor with a matching frequency, and restarting the motor with the input frequency. (See examples 1, 2, and 3.)

Even when restarting with matching frequency has been selected, the inverter restarts the motor with 0 Hz if it detects a frequency lower than the restart frequency threshold (b007).

The settings, including that of the FRS terminal, which you make for this function will affect the inverter operation at recovery of the motor from the free-running status.

Item	Function code	Data or range of data	Description
Restart mode after	b088	00	Start with 0 Hz (See example 1.)
		01	Start with matching frequency (See example 2.)
FRS
		02	Restart with input frequency (See example 3.)
Retry wait time before	b003	0.3 to 100. (s)	Time to wait until restarting the motor
motor restart
Restart frequency	b007	0.00 to 400.0 (Hz)	Setting of the minimum level for frequency
threshold			adjustment
Active frequency	b028	"0.20 x rated current" to
matching, scan start
		"2.00 x rated current"
frequency
Active frequency
matching, scan-time	b029	0.10 to 30.00 (s)
constant
Active frequency		00	Frequency set when the inverter output has
			been shut off
matching, restart	b030
		01	Maximum frequency
frequency select
		02	Newly set frequency
(Example 1) Restarting with 0 Hz		(Example 2) Restarting with matching frequency

FW

FRS

Motor speed

0

	FW
	FRS
Free-running		Free-running
	Motor
	speed
Restarting with 0 Hz	0	b003
		Restarting with
		matching frequency

The inverter restarts the motor with 0 Hz regardless of the motor speed. The setting of retry wait time is ignored for restarting with 0 Hz.

If the inverter restarts the motor with 0 Hz when the motor speed is high, the inverter may trip because of overcurrent.

The inverter waits for the retry wait time after the FRS terminal has been turned off, detects the motor speed (frequency), and restarts the motor with the matching frequency without stopping it. If the inverter trips because of overcurrent when it restarts the motor with matching frequency, prolongs the retry wait time.

Even when restarting with matching frequency has been selected, the inverter may start the motor with 0 Hz if:

1)the output frequency is no more than half the base frequency or

2)the voltage induced on the motor is attenuated quickly.

4 - 52