Hitachi SJ100 Dynamic Braking Usage Ratio

5–6

Dynamic Braking

Dynamic Braking Usage Ratio

The inverter controls braking via a duty cycle	BRD
method (percent of the time braking is ON			t1			t2		t3
versus total time). Parameter B_90 sets the	ON
dynamic braking usage ratio. In the graph to
the right, the example shows three uses of	OFF
dynamic braking in a 100-second period. The
inverter calculates the average percentage
				(t1 + t2 + t3)					t
usage in that time (T%). The percentage of
			T% =				⋅	100
		B 90		------------------------------
usage is proportional to the heat dissipated. If					100 seconds

T% is greater than the B_90 parameter setting,

the inverter enters the Trip Mode and turns OFF the frequency output.

Please note the following:

•When B_90 is set for 0%, dynamic braking is not performed.

•When the T% value exceeds the limit set by B_90, dynamic braking ends.

•When mounting an external dynamic braking unit, set the usage ratio (B_90) 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.

Motor Control Accessories