Allen-Bradley 20G - Page 17

Rockwell Automation Publication PFLEX-AT001L-EN-P - September 2017 17
Determining Dynamic Brake Requirements Chapter 2
The Average Power in watts regenerated over the period t
4
is:
Calculate Average Power in watts regenerated over the period
t
4
:
Record Average Power in watts regenerated over the period
t
4
:
Step 4 – Percent Average Load of the Internal Dynamic Brake Resistor
Skip this calculation if an external dynamic brake resistor will be used.
AL = Average load in percent of dynamic brake resistor.
P
av
= Average dynamic brake resistor dissipation calculated in Step 3
– Minimum Power Requirements for the Dynamic Brake
Resistors on page 16 (watts)
P
db
= Steady state power dissipation capacity of dynamic brake
resistors obtained from
Appendix A (watts)
Calculate Percent Average Load of the dynamic brake resistor:
Record Percent Average Load of the dynamic brake resistor:
The calculation of
AL is the Dynamic Brake Resistor load expressed as a percent. P
db
is the sum of the Dynamic Brake dissipation capacity and is obtained from the
P
av
=
IMPORTANT The value of AL should not exceed 100%.
AL=
P
av
t
3
t
2
–
t
4
------------------
P
b
2
------

b

o
+

b
------------------------=
P
av
oooooo oooooo–
oooooo
--------------------------------------------------
oooooo
2
------------------------
oooooo oooooo+
oooooo
--------------------------------------------------=
AL
P
av
P
db
--------- 100=
AL
oooooooooo
oooooooooo
------------------------------------- - 100=