ABB ACS580-04 - Selecting a Custom Brake Resistor

power of the motor ( P
br
) is 300 kW. The duration of a braking cycle (T) is 3 minutes.
Thus, the number of braking pulses in 400 s is 2.2. The braking time ( t
br
) is 20 s.
P
br
(300 kW) is less than P
brcont
(315 kW). This is permitted.
The energy generated by the motor during a 400 s period is 2.2 × 300 kW × 20 s =
13200 kJ. The preselected brake resistor withstands an energy pulse of 10800 kJ in a
400 s period. In this case, the resistor is too small. Decrease the braking power or
braking time, or select a custom brake resistor as described in section Selecting a
custom brake resistor (page 244).
￭ Selecting a custom brake resistor
If you use other than ABB resistor,
1. make sure that the resistance of the custom resistor is greater than or equal to
the resistance of the default ABB resistor.
where
Resistance of the custom resistor R
Resistance of the default resistor R
min
WARNING!
Never use a brake resistor with a resistance smaller than R
min
. This will
cause overcurrent that will damage the brake chopper and the drive.
2. make sure that the resistance of the custom resistor does not restrict the braking
capability needed, ie.
where
Maximum power generated by the motor during braking P
max
Drive intermediate DC circuit voltage. U
DC
1.35 · 1.2 · 415 V DC (when supply voltage is 380 … 415 V AC)
1.35 · 1.2 · 500 V DC (when supply voltage is 440 … 500 V AC) or
1.35 · 1.2 · 690 V DC (when supply voltage is 525 … 690 AC)
Resistance of the custom resistor R
3. make sure that the resistor can dissipate the energy transferred to it during the
braking:
• Braking energy is not greater than the resistor heat dissipation capacity ( E
r
)
during the period specified. See the custom resistor specification.
• The resistor is installed in a correctly ventilated and cooled space. Otherwise
the resistor cannot meet its heat dissipation capacity and overheats.
4. make sure that the instantaneous load capacity of the custom resistor is greater
than the maximum power taken by the resistor when it is connected to the drive
intermediate DC circuit by the chopper:
244 Resistor braking