SJ700-2 Instruction Manual NT204DX - Hitachi America, Ltd.

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
00 Start with 0 Hz (See example 1.)
Restart mode after
b088
01 Start with matching frequency (See example 2.)
FRS
02 Restart with input frequency (See example 3.)
Retry wait time before
motor restart
b003 0.3 to 100. (s) Time to wait until restarting the motor
Restart frequency
Setting of the minimum level for frequency
b007 0.00 to 400.0 (Hz)
threshold
adjustment
Active frequency
matching, scan start
frequency
b028
"0.20 x rated current" to
"2.00 x rated
current"
Active frequency
matching, scan-time
constant
Active frequency
matching, restart
frequency select
b029
b030
(NOTE):applied for 75 to 150kW
(Example 1) Restarting with 0 Hz
0.10 to 30.00 (s)
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
00
Frequency set when the inverter output has
been shut off
01 Maximum frequency
02 Newly set frequency
(Example 2) Restarting with matching frequency
FW
FW
FRS
Motor
speed
0
Free-running
Restarting with 0 Hz
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.
4 - 53
FRS
Motor
speed
0
b003
Free-running
Restarting with
matching frequency
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.