• no danger of overheating is caused to the resistor or nearby materials, and
• the temperature of the room the resistor is located in does not exceed the allowed
maximum.
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 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.
ABB requires that the resistor has a thermal switch (standard in ABB resistors) which is
wired to the chopper for safety reasons. The thermal switch cable must be shielded and
may not be longer than the resistor cable. For wiring, see section Connection
procedure (page 233).
￭ Protecting the resistor cable against short-circuits
The DC fuses for the brake chopper protection protect also the resistor cable against
short-circuits.
Mechanical installation of resistors
All brake resistors must be installed outside the drive. Obey the resistor manufacturer’s
instructions.
Electrical installation
￭ Measuring the insulation of the brake resistor circuit
WARNING!
Obey the safety instructions of the drive. If you ignore them, injury or death, or
damage to the equipment can occur.
If you are not a qualified electrical professional, do not do installation or
maintenance work.
232 Resistor braking
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