Supply the resistor with cooling air or coolant according to the resistor manufacturer’s
instructions.
WARNING!
The materials near the brake resistor must be non-flammable. The surface
temperature of the resistor is high. Air flowing from the resistor is of hundreds of
degrees Celsius. If the exhaust vents are connected to a ventilation system, make
sure that the material withstands high temperatures. Protect the resistor against
contact.
Protecting the system in brake circuit fault situations
￭ Protecting the system in cable and brake resistor short-circuit situations
The drive input fuses will also protect the resistor cable when it is identical with the input
power cable.
￭ Protecting the system against thermal overload
The drive has a brake thermal model which protects the brake resistor against overload.
ABB recommends to enable the thermal model at start up.
Equipping the drive with a main contactor is highly recommended for safety reasons
even when you have enabled the resistor thermal model. 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 recommends that you
use resistors equipped with a thermal switch (1) inside the resistor assembly. The switch
indicates overtemperature.
Resistor braking 177
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