4-2
Record the Values Calculated in Section 2
Calculate Maximum Dynamic Brake Resistance Value
R
db1
= Maximum allowable value for the dynamic brake resistor
(ohms)
V
d
= DC bus voltage the chopper module regulates to
(375V DC or 750V DC)
P
b
= Peak breaking power calculated in Section 2: Step 3
(watts)
Calculate Maximum Dynamic Brake Resistance:
Record Maximum Dynamic Brake Resistance:
The choice of the Dynamic Brake resistance value should be less than
the value calculated in this step. If the value is greater, the drive can trip
on DC bus overvoltage. Do not reduce P
b
by any ratio because of
estimated losses in the motor and inverter. This has been accounted for
by an offsetting increase in the manufacturing tolerance of the resistance
value and the increase in resistance value due to the temperature
coefficient of resistor element.
P
b
=
P
av
=
R
db1
=
R
db1
0.9 V
d
()
2
×
P
b
--------------------------=
R
db1
0.9 ooooooooo()
2
×
ooooooooo[]
-----------------------------------------------=
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