Hitachi CONVENTION 14 Instruction Manual page 125

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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
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
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.
The figure at below right describes how
Frequency pull-in resume operates. After
waiting the time set in B003, the inverter
tries to catch the speed of the motor shaft
and outputs the speed set in B011. At this
time, if the motor current rises up to the
value set in B030, the inverter decreases the
frequency according to the deceleration time
set in B029, and finally comes to the
required speed. Following are the related
parameters for this control.
Code
B011
B029
B030
B088
B091
frequency pull-in ). The run command may turn OFF briefly, allowing the motor to
Parameter contents
Start freq to be used in case of freq
matching restart
Deceleration rate of frequency matching
restart setting
Current level of frequency matching
restart setting
Restart mode after FRS
Stop mode selection
page 3-32), or an intelligent input terminal [FRS]
Zero frequency resume
B091 = 01
B088 = 00
[FRS]
0
Motor
speed
0
Frequency pull-in resume
B091 = 01
B088 = 01
[FRS]
0
Wait time
Motor
speed
0
Motor
current
RMS
0
Stop mode = free-run stop
Resume from 0Hz
Zero-frequency start
Stop mode = free-run stop
Resume from current speed
B011
B029
B003
B030
t
t
t
t
t