Eaton PowerXL DC1 20 Series Installation Manual page 51

Selecting brake resistors
Brake resistors are selected based on continuous power dissipation P
maximum peak pulse power P
The brake resistor must be adequate for both powers.
The maximum pulse power is defined by the braking torque – kinetic energy
W during braking – that is fed back by the motor during braking.
kin
A simplified method that can be used is to take the variable frequency drive's
braking power P or the rated motor output and use it as peak pulse power
max
P for sizing purposes, since the mechanical braking power will be
Peak
reduced by the motor's and inverter's efficiency.
The required rated power / continuous rating for braking resistance P
calculated using braking energy W
If the kinetic energy is not known, you will need the ratio of braking time
t to cycle time t
Braking
The required continuous rating for a duty factor of 10% (= DF[%]),
for example, can be calculated as follows:
This means that the brake resistor's continuous rating P
lower than maximum pulse power P
Resistance R must be at least as high as the breaking transistor's minimum
B
permissible resistance R
￫
Use brake resistors with the recommended R
values for the DC1 variable frequency drives' ratings.
￫
For the rated braking resistances for DC1 variable frequency
drives, please refer to ￫ Section 2.7, "Braking resistances",
page 45.
DC1...20... and DC1...OE1 Variable Frequency Drives 02/20 MN040059EN www.eaton.com
.
Peak
1
P ∼ P = x
Peak max
2 t
and cycle time t
kin
W
kin
P =
DB
t
C
:
C
t
Braking
DF[%] = x 100 %
t
C
P = P x 10 %
DB Peak
by the DF[%] factor.
Peak
.
min
2.7 Braking resistances
W
kin
Braking
:
C
will always be
DB
resistance
Brec
2 Engineering
and
DB
is
DB
47