Selecting And Routing The External Brake Resistor Cables; Minimizing Electromagnetic Interference; Maximum Cable Length - ABB ACS880-07 Hardware Manual

224 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
capacity of the resistor can be calculated from the following equation:
P <
max
where
P
max
U
DC
R
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.
Check the resistor selection. The energy generated by the motor during a 400-second
period must not exceed the resistor heat dissipation capacity E
Note: If the E value is not sufficient, it is possible to use a four-resistor assembly in which
R
two standard resistors are connected in parallel, two in series. The E
resistor assembly is four times the value specified for the standard resistor.

Selecting and routing the external 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.

Minimizing electromagnetic interference

Follow these rules in order to minimize electromagnetic interference caused by the rapid
current changes in the resistor cables:
•
Shield the braking power line completely, either by using shielded cable or a metallic
enclosure. Unshielded single-core cable can only be used if it is routed inside a
cabinet that efficiently suppresses the radiated emissions.
•
Install the cables away from other cable routes.
•
Avoid long parallel runs with other cables. The minimum parallel cabling separation
distance should be 0.3 meters.
•
Cross the other cables at right angles.
•
Keep the cable as short as possible in order to minimize the radiated emissions and
stress on chopper IGBTs. The longer the cable the higher the radiated emissions,
inductive load and voltage peaks over the IGBT semiconductors of the brake chopper.

Maximum cable length

The maximum length of the resistor cable(s) is 10 m (33 ft).
2
U
DC
R
Maximum power generated by the motor during braking
Voltage over the resistor during braking. U
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)
Resistor resistance (ohm)
. The braking power
min
equals to
DC
.
R
value of the four-
R