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L2002 Inverter
Configuring
Drive Parameters
3–43
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” on page 3–33), 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.
Stop Mode = free-run stop
B091
=
01 B091
=
01
B088
=
00 B088
=
01
[FW, RV]
Motor
speed
t
Resume from 0Hz
Zero-frequency start
t
Stop Mode = free-run stop
Resume from current speed
[FW, RV]
Motor
speed
Wait time
B003
“B” Function Run
Mode
Edit
Lo Hi
Defaults
Func.
Code
Name /
SRW Display
Description
–FE(F)
(EU)
–FU
(USA)
Units
B088 Restart mode after FRS Selects how the inverter
resumes operation when the
free-run stop (FRS) is
cancelled, two options:
00 .. Restart from 0Hz
01 .. Restart from frequency
detected from real speed of
motor (frequency matching)
✘ ✔ 00 00 —
RUN FRS ZST