Selecting and routing the brake resistor cables
Use a shielded cable specified in the technical data.
￭ Minimizing electromagnetic interference
Follow 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 the radiated emissions.
• Install the cables away from other cable routes.
• Avoid long parallel runs with other cables. The minimum parallel cabling separation
distance is 0.3 meters (1 ft).
• Cross the other cables at 90 degree 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 greater the radiated emissions,
inductive load and voltage peaks over the IGBT semiconductors of the brake chopper.
Note: ABB has not verified that the EMC requirements are fulfilled with custom brake
resistors and cabling. The customer must consider the EMC compliance of the complete
installation.
￭ Maximum cable length
The maximum length of the resistor cable(s) is 10 m (33 ft).
Placing custom brake resistors
Install the resistors outside the drive in a place where they are able to cool effectively.
Arrange the cooling of the resistor in a way that
• 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 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.
144 Resistor braking
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