￭ Calculating the maximum allowed braking power for a custom duty
cycle – ABB chopper and custom 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 factory-installed brake choppers and custom
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 60 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 60 seconds every 600 seconds. See the value in the ratings
of the factory-installed brake choppers and custom resistors.
P
br,max
Example 1
The duration of a braking cycle is three minutes. The braking time is 15 minutes.
1.
P
br
≤ P
br,max
2.
n × P
br
× t
br
≤ P
br,max
× 60 s
1 × P
br
× 600 s ≤ P
br,max
× 60 s
P
br ≤ P
br,max
× 60/600 s = 0.1× P
br,max
-> The allowed continuous braking power is 10% of the maximum braking power
(Pb
r,max
). This fulfills also condition 1.
Example 2
The duration of a braking cycle (T) is three minutes = 3 × 60 s = 180 s. The braking time
(t
br
) is 30 seconds.
230 Resistor braking
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