ABB ACS880-604LC, Hardware Manual

Page: 26 / 104

Example 3
The duration of a braking cycle is three minutes. The braking time is 10 seconds.
1.
„
„
„
P
br
<
P
brmax
· 100 s
4 · 10 s
=
2.5 · P
brmax
„
„
„
t
br
P
brmax
t
P
br
600 s
T = Duration of braking cycle
2. P
br
> P
brmax
Not allowed.
Result: The maximum allowed braking power for the cycle is equal to the maximum braking
power (
P
brmax
).
Selecting and routing the brake resistor cables
For the recommended copper cable for connecting a brake resistor to the brake chopper,
see
Brake circuit cable sizes (page 78) .
￭ Minimizing electromagnetic interference
Obey 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 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 m (1 ft).
• 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 cable length of the resistor cable or cables is 50 m (164 ft).
26 Planning the installation