Hardware Manual

246 Resistor braking
 Protecting the system against thermal overload
The brake chopper protects itself and the resistor cables against thermal overload
when the cables are dimensioned according to the nominal current of the drive. The
drive control program includes a resistor and resistor cable thermal protection
function which can be tuned by the user. See the firmware manual.
Frames R1 to R4
Equipping the drive with a main contactor is highly recommended for safety reasons.
Wire the contactor so that it opens in case the resistor overheats. This is essential for
safety since the drive will not otherwise be able to interrupt the main supply if the
chopper remains conductive in a fault situation. An example wiring diagram is shown
below. ABB resistors are equipped with a thermal switch (1) inside the resistor
assembly as standard. The switch indicates overtemperature and overload.
We recommend that you also wire the thermal switch to a digital input of the drive.
Frames R5 to R9
A main contactor is not required for protecting against resistor overheating when the
resistor is dimensioned according to the instructions and the internal brake chopper is
in use. The drive will disable power flow through the input bridge if the chopper
remains conductive in a fault situation but the charging resistor may fail.
Note: If an external brake chopper (outside the drive module) is used, a main
contactor is always required.
ACS880
L1 L2 L3
1
2
3
4
5
6
13
14
3
4
1
2
K1

OFF
ON
L1 L2 L3
1
ACS880
+24VD x
DIx x