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B091/B088: Stop Mode / Restart Mode Configuration – You can configure how the
inverter performs a standard stop (each time Run FWD and REV signals turn OFF).
Setting B091 determines whether the inverter will control the deceleration, or whether
it will perform a free-run stop (coast to a stop). When using the free-run stop selection,
it is imperative to also configure how you want the inverter to resume control of motor
speed. Setting B088 determines whether the inverter will ensure the motor always
resumes at 0 Hz, or whether the motor resumes from its current coasting speed (also
called
frequency pull-in
). The run command may turn OFF briefly, allowing the motor to
coast to a slower speed from which normal operation can resume.
In most applications a controlled deceleration is desirable, corresponding to B091=00.
However, applications such as HVAC fan control will often use a free-run stop
(B091=01). This practice decreases dynamic stress on system components, prolonging
system life. In this case, you will typically set B088=01 in order to resume from the
current speed after a free-run stop (see diagram down below: frequency pull-in resume).
Note that using the default setting, B088=00, can cause trip events when the inverter
attempts to force the load quickly to zero speed.
NOTE: Other events can cause (or be configured to cause) a free-run stop, such as power
loss (see “Automatic Restart Mode” on page 3-32), or an intelligent input terminal [FRS]
signal. If all free-run stop behavior is important to your application (such as HVAC), be
sure to configure each event accordingly.
An additional parameter further configures
all instances of a free-run stop. Parameter
B003, Retry Wait Time Before Motor Restart,
sets the minimum time the inverter will
free-run. For example, if B003 = 4 seconds
(and B091=01) and the cause of the free-run
stop lasts 10 seconds, the inverter will free-
run (coast) for a total of 14 seconds before
driving the motor again.
Further explanation of the Frequency pull-
in resume: In the figure below: Frequency
pull-in resume, after waiting time set in
B003, inverter tries to catch the speed and
outputs the speed set in B011. At this
moment, if the motor current rises up to the
value set in B030, the inverter decreases the
speed according to the deceleration time set
in B029, and finally comes to the required
speed. Following are the related parameters
for this control.
Code Parameter contents
B011 Start freq to be used in case of freq
matching restart
B029 Deceleration rate of frequency matching
restart setting
B030 Current level of frequency matching
restart setting
B088 Restart mode after FRS
B091 Stop mode selection
Motor
speed
Stop mode = free-run stop
B091 = 01
0
t
[FRS]
0
t
Resume from 0Hz
B088 = 00
Zero-frequency start
Zero frequency resume
Motor
speed
Stop mode = free-run stop
B091 = 01
0
t
[FRS]
0
t
Resume from current speed
B088 = 01
Wait time
B003
0
t
Motor
current
RMS
B011
B030
B029
Frequency pull-in resume
3−42
Configuring Drive
Parameters