Filter
Top Products
“B” Group: Fine-Tuning Functions
Configuring Drive
Parameters
3–40
Miscellaneous functions, continued...
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 deter-
mines 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 matching). 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 below, right). 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 and Phase Loss” on page 3–28), and inverter trip events in
general (see “
Miscellaneous Functions” on page 3–55). If all free-run stop behavior is impor-
tant to your application (such as HVAC), be sure to configure each event accordingly.
Some additional parameters further configure 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. Parameter B007, Restart Frequency Threshold, sets the motor frequency at which the
inverter will no longer resume and accelerate, instead resuming from 0 Hz (complete stop).
2
Motor
speed
[FW, RV]
Zero-frequency start
Motor
speed
Resume from current speed
wait time
[FW, RV]
B003
B088=01B088=00
Resume from 0Hz
B091=01
Stop Mode = free-run stop
B091=01
Stop Mode = free-run stop
tt
“B” Function
Run
Mode
Edit
Lo Hi
Defaults
Units
SRW Display
Func.
Code
Name Description
–FE2
(CE)
–FU2
(UL)
–FR
(Jpn)
B088 Restart mode after FRS Selects how the inverter
resumes operation when the
free-run stop (FRS) is
cancelled, two option codes:
00 Restart from 0Hz
01 Restart from frequency
detected from actual
speed of motor
✘ ✔ 00 00 00 —
>b088 RUN
FRS ZST