Dynamic Braking
Motor Control
Accessories
5–6
Dynamic Braking Usage Ratio
The inverter controls braking via a duty cycle
method (percent of the time braking is ON
versus total time). Parameter B090 sets the
dynamic braking usage ratio. In the graph to
the right, the example shows three uses of
dynamic braking in a 100-second period. The
inverter calculates the average percentage
usage in that time (T%). The percentage of
usage is proportional to the heat dissipated. If
T% is greater than the B090 parameter setting,
the inverter enters the Trip Mode and turns OFF the frequency output.
Please note the following:
• When B090 is set for 0%, dynamic braking is not performed.
• When the T% value exceeds the limit set by B090, dynamic braking ends.
• When mounting an external dynamic braking unit, set the usage ratio (B090) to 0.0
and remove the external resistors.
• The cable from the external resistor to the inverter must not exceed 5 m (16 ft.) length.
• The individual wires from the resistor to the inverter must not be bundled together.
BRD
T%
t1 t2 t3++()
100 seconds
-------------------------------
100×=
B90
ON
OFF
t1 t2 t3
t
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