Selecting A Custom Resistor - ABB ACS880-07 Hardware Manual

252 Resistor braking
Note: If the E value of the resistor is not sufficient, it is possible to use a four-resistor
R
assembly in which two resistors are connected in parallel, two in series. The E
of the four-resistor assembly is four times that of a single resistor.

Selecting a custom resistor


If you use a resistor other than the default resistor, make sure that:
1. The resistance of the custom resistor is greater or equal than the resistance of the
default resistor in the rating table on page 256:
R > R
min
where
R
R
min
2. The load capacity of the custom resistor is higher than the instantaneous maximum
power consumption of the resistor when it is connected to the drive DC link voltage by
the chopper:
U
P >
r
where
P
r
U
DC
R
Selecting and routing the cables of a custom resistor

Use the same cable type for the resistor cabling as for the drive input cabling to ensure
that the input fuses also protect the resistor cable. Alternatively, a two conductor shielded
cable with the same cross-sectional area can be used.
Resistance of the custom resistor.
WARNING! Never use a brake resistor with a resistance below the value
specifed for the particular drive / brake chopper / resistor combination. The
drive and the chopper would not able to handle the overcurrent caused by
the low resistance.
Resistance of the default resistor
2
DC
R
Load capacity of the custom resistor
Drive DC link voltage.
1.35 · 1.25 · 415 V DC (when supply voltage is 380 to 415 V AC)
1.35 · 1.25 · 500 V DC (when supply voltage is 440 to 500 V AC) or
1.35 · 1.25 · 690 V DC (when supply voltage is 525 to 690 V AC)
Resistance of the custom resistor
value
R