Hitachi WJ200-001S Instruction Manual page 111

326
DC Braking (DB) Settings
Normal DC braking performance The DC
braking
stopping torque when compared to a normal
deceleration to a stop. DC braking is
particularly useful at low speeds when
normal deceleration torque is minimal.
When you set  to  (Enable during stop), and the RUN command (FW/RV signal)
turns OFF, the inverter injects a DC voltage into the motor windings during
deceleration below a frequency you can specify ().
The braking power () and duration () can both be set. You can optionally specify
a wait time before DC braking (), during which the motor will free run.
DC Braking – Frequency Detection  You can instead set DC braking to operate during
RUN mode only, by setting  to  (Frequency detection). In this case DC braking
operates when the output frequency comes down to the one you specified in  while
the RUN command is still active. Refer to the graphs figures below.
External DB and Internal DC braking are invalid during the frequency detection mode.
FW
ON
F-SET

F-OUT
Ex.1) Step change in F-SET.
Example 1, (above left) shows the performance with = with a step-changing
frequency reference. In this case, when the reference goes to 0, the inverter immediately
starts DC braking because the set point drops below the value specified in . DC
braking continues until the set point exceeds . There will be no DC braking at next
downward transition because the FW input is OFF.
Example 2, (above right) shows a gradually changing frequency reference, for example
by analog input. In this case, there will be a DC braking period at starting because the
frequency set point is lower than the value specified in .
feature can provide
DB
+
Running
additional
0
-
FW
ON
F-SET

F-OUT
DB
Ex.2) Analog change in F-SET.
Free run DC brake
t
 
DB DB