ABB ACS880-01 Series, Hardware Manual

Page: 212 / 224

212 Resistor braking
Note : A custom resistor can be selected within the limits imposed by the internal
brake chopper of the drive:
•
The resistance value of the custom resistor is at least R
min
. The braking power
capacity of the resistor can be calculated from the following equation:
WARNING! Never use a brake resistor with a resistance below the
value specified for the particular drive / brake chopper / resistor
combination. The drive and the chopper are not able to handle the overcurrent
caused by the low resistance.
3. Check the resistor selection. The energy generated by the motor during a 400-
second period must not exceed the resistor heat dissipation capacity E
R
.
Note : If the E
R
value is not sufficient, it is possible to use a four-resistor assembly in
which two standard resistors are connected in parallel, two in series. The E
R
value of
the four-resistor assembly is four times the value specified for the standard resistor.
„
Selecting and routing the brake resistor cables
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.
where
P
max
Maximum power generated by the motor during braking
U
DC
Voltage over the resistor during braking. U
DC
equals to
1.35 · 1.25 · 240 V DC (when supply voltage is 208 to 240 V AC)
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 AC)
R Resistor resistance (ohm)
P
max
<
U
DC
R
2
ACS880-01 HW.book Page 212 Monday, July 1, 2013 4:51 PM