ABB ACS880-07 - Minimizing Electromagnetic Interference; Selecting and Routing the Cables of a Custom Resistor

1. Braking energy transferred during any ten minute period must be less than or
equal to the energy transferred during the reference braking cycle (1/9 min).
2. The maximum braking power for a custom braking cycle ( P
br
) must not exceed
the rated maximum value P
brmax
.
The rules as equations:
1. n × P
br
× t
br
≤ P
brmax
× 60 s => P
br
≤ ( P
brmax
× 60 s)/(n × t
br
)
2. P
br
≤ P
brmax
Number of braking pulses during a 10-minute periodn
Maximum braking power (kW) for a custom braking cycle P
br
Braking time (s) t
br
Maximum braking power for a reference braking cycle (1 minute of braking, 9 minutes of rest) P
brmax
Example 1
The duration of a braking cycle is 30 minutes. The braking time is 15 minutes.
Result: If the braking time exceeds 10 minutes, the braking is considered continuous.
The allowed continuous braking power is 10% of maximum braking power ( P
brmax
).
Example 2
The duration of a braking cycle ( T ) is three minutes. The braking time ( t
br
) is 40 seconds.
1. n × P
br
× t
br
≤ P
brmax
× 60 s => P
br
≤ ( P
brmax
× 60 s) / (4 × 40 s) = 0.375 × P
brmax
2. P
br
≤ P
brmax
<=> 0.375 × P
brmax
≤ P
brmax
OK
Result: The maximum braking power for the custom braking cycle is 37% of the rated
value given for the reference cycle.
￭
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.
Minimizing electromagnetic interference
Make sure that the installation is compliant with the EMC requirements. Obey these
rules in order to minimize electromagnetic interference caused by the rapid voltage
and current changes in the resistor cables:
• Shield the brake resistor cable. Use shielded cable or a metallic enclosure. If you
use unshielded single-core cables, route them 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 is 0.3 meters (1 ft).
• Cross the other cables at 90° angles.
• Keep the cable as short as possible in order to minimize the radiated emissions
and stress on the brake chopper. The longer the cable the greater the radiated
emissions, inductive load and voltage peaks over the IGBT semiconductors of the
brake chopper.
338 Resistor braking