ABB ACS350 Series, User Manual

Page: 302 / 314

Technical data
302
Brake resistors
ACS350 drives have an internal brake chopper as standard equipment. The brake
resistor is selected using the table and equations presented in this section.
Brake resistor selection
1. Determine the required maximum braking power P
Rmax
for the application. P
Rmax
must be smaller than P
BRmax
given in the table on page 303 for the used drive
type.
2. Calculate resistance R with Equation 1.
3. Calculate energy E
Rpulse
with Equation 2.
4. Select the resistor so that the following conditions are met:
• The rated power of the resistor must be greater than or equal to P
Rmax
.
• Resistance R must be between R
min
and R
max
given in the table for the used
drive type.
• The resistor must be able to dissipate energy E
Rpulse
during the braking
cycle T .
Equations for selecting the resistor:
where
R = selected brake resistor value (ohm)
P
Rmax
= maximum power during the braking cycle (W)
P
Rave
= average power during the braking cycle (W)
E
Rpulse
= energy conducted into the resistor during a single braking pulse (J)
t
on
= length of the braking pulse (s)
T = length of the braking cycle (s).
P
Rmax
·
150000
P
Rmax
P
Rave
=
t
on
T
R =
t
on
P
Rmax
P
Rave
T
Eq. 1.
Eq. 3.
For conversion, use 1 HP = 746 W.
450000
P
Rmax
U
N
= 200…240 V:
U
N
= 380…415 V: R =
P
Rmax
· E
Rpulse
= t
on
Eq. 2.
615000
P
Rmax
U
N
= 415…480 V: R =