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• 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.
Selecting the resistor thermal switch circuit cable
Make sure that the cable in the resistor thermal switch circuit meets the following
requirements:
• shielded cable
• rated operating voltage between a core and ground > 750 (U
• insulation test voltage > 2.5 kV
• jacket material for at least 90 °C (194 °F). Take into account further requirements due
to resistor construction and temperature.
Protecting the system against thermal overload
The brake control program includes a resistor and resistor cable thermal protection function,
which can be tuned by the user. The brake chopper protects itself and the resistor cables
against thermal overload. Make sure that the resistor assembly is equipped with a thermal
switch, which is wired to disable the chopper (and/or switch off the supply to the drive) in
case of overtemperature.
For more information on the thermal protection function, see the appropriate firmware
manual.
Protecting the system against short-circuits
The brake unit is equipped with fuses as standard.
The fuses protect the brake chopper, the brake resistor and the brake circuit cables in a
short-circuit situation.
Guidelines for planning the electrical installation 33
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