￭ Selecting and routing the brake resistor cablesUse the same cable type for resistor as for inverter input cabling to ensure that the inverterDC fuses also protect the resistor cable.Minimizing electromagnetic interferenceFollow these rules in order to minimize electromagnetic interference caused by the rapidcurrent changes in the resistor cables:• Shield the braking power line completely, either by using shielded cable or a metallicenclosure. Unshielded single-core cable can only be used if it is routed inside a cabinetthat efficiently suppresses the radiated emissions.• Install the cables away from other cable routes.• Avoid long parallel runs with other cables. The minimum parallel cabling separationdistance should be 0.3 meters (1 ft).• Cross the other cables at right angles.• Keep the cable as short as possible in order to minimize the radiated emissions andstress 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 resistorsand cabling. The customer must consider the EMC compliance of the complete installation.Maximum cable lengthThe maximum cable length of the resistor cable is 10 m (33 ft).￭ Placing custom brake resistorsInstall 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 allowedmaximum.Supply the resistor with cooling air or coolant according to the resistor manufacturer’sinstructions.WARNING!The materials near the brake resistor must be non-flammable. The surfacetemperature of the resistor is high. Air flowing from the resistor is of hundreds ofdegrees Celsius. If the exhaust vents are connected to a ventilation system, makesure that the material withstands high temperatures. Protect the resistor againstcontact.￭ Protecting the system against thermal overloadThe inverter module protects itself and the resistor cable against thermal overload whenthe cable is correctly dimensioned. The inverter control program includes a resistor andresistor cable thermal protection function which can be tuned by the user. See the firmwaremanual.Equipping the drive system with a main contactor or breaker is highly recommended forsafety reasons. Wire the contactor or breaker so that it opens in case the resistor overheats.Resistor braking using frames R1i…R4i inverter modules 331
