ABB ACS880-34 Series - Calculating the Maximum Allowed Braking Power for a Custom Duty Cycle - ABB Chopper and ABB Resistor; Example; Selecting the Default Brake Circuit Components - ABB Brake Chopper and Custom Resistor

3. See the pre-selected chopper and the pre-selected resistor for the drive from the technical
data of the ABB brake choppers and resistors.
4. Check the pre-selection of the chopper and resistor: Is your braking cycle 1/5 min or
10/60 s?
a. If yes: Is your braking power smaller than the value for the cycle given in the ratings
of the ABB resistors? If yes: the pre-selected chopper and resistor combination is
ok for the drive.
b. If no: Verify the pre-selected chopper and resistor according to the instructions given
in section Calculating the maximum allowed braking power for a custom duty cycle
– ABB chopper and ABB resistor (page 228).
￭ Calculating the maximum allowed braking power for a custom duty
cycle – ABB chopper and ABB resistor
The maximum allowed braking power for the customer braking cycle must meet both of the
conditions 1 and 2 below.
1. The braking power of the custom duty cycle must not be greater than the maximum
braking power given in the ratings of the ABB choppers and resistors.
2. The braking energy transferred during any 600-second period must be smaller than or
equal to the energy that is transferred during the reference braking cycle of 40 seconds
every 600 seconds:
where
Number of the braking pulses during the 600-second periodn
Braking power of the custom duty cycle in kW
P
br
Braking time within the custom duty cycle in seconds
t
br
Maximum braking power allowed for 40 seconds every 600 seconds. See the value in the ratings
of the ABB choppers and resistors. (The ABB resistor does not withstand the 60-second cycle
of the brake chopper.)
P
br,max
Example
Drive: ACS880-34-585A-3 with P
N
of 315 kW. Chopper: NBRA-659. ABB resistor:
2xSAFUR180F460. The braking power is 300 kW. The duration of a braking cycle (T) is
three minutes -> number of braking pulses in 600 seconds = 3.3. The braking time (t
br
) is
30 seconds.
1.
P
br
= 300 kW < P
br,max
= 355 kW. This is ok.
2. 3.3 × 300 kW × 30 s = 29700 kJ. 355 kW × 40 s = 14200 kJ which is not greater than
29700 kJ. -> Decrease the braking power to smaller than 143 kW or braking time to
14 s.
￭ Selecting the default brake circuit components - ABB brake chopper
and custom resistor
1. Calculate the maximum power generated by the motor during braking and define the
braking cycle.
2. Select a drive and brake chopper combination. The reference braking cycle is 60 seconds
in every 600 seconds.
228 Resistor braking