Guidelines for planning the electrical installation 59 Protecting the motor insulation and bearingsThe drive uses modern IGBT inverter technology. Regardless of frequency, the driveoutput has pulses of approximately the drive DC bus voltage with a very short rise time. Upto twice bus voltage can be at the motor terminals, depending on the attenuation andreflection properties of the motor cable and the terminals. The increased voltage cancause additional stress on the motor and motor cable insulation.Modern variable speed drives with their fast rising voltage pulses and high switchingfrequencies can generate current pulses that flow through the motor bearings. This cangradually erode the bearing races and rolling elements.Optional du/dt filters protect motor insulation system and reduce bearing currents. Optionalcommon mode filters mainly reduce bearing currents. Insulated N-end (non-drive end)bearings protect the motor bearings. Requirements tableThe following table shows how to select the motor insulation system and when optionalABB du/dt filters, insulated N-end (non-drive end) motor bearings and ABB common modefilters are required. Failure of the motor to fulfill the following requirements or improperinstallation may shorten motor life or damage the motor bearings and voids the motorwarranty.Motor type Nominal AC supplyvoltageRequirement forMotor insulation system ABB du/dt and common modefilters, insulated N-end motorbearingsABB motorsRandom-wound M2_,M3_ and M4_UN < 500 V Standard + N + CMFForm-woundHX_ and AM_380 V < UN < 690 V Standard PN < 500 kW:+N + CMFPN > 500 kW+N + du/dt + CMFOld* form-wound HX_and modular380 V < UN < 690 V Check with the motor manufacturer.Random-wound HX_and AM_ **0 V < UN < 500 V Enamelled wire with fiberglass taping+ N + CMFHDP Consult the motor manufacturer.* manufactured before 1.1.1998** For motors manufactured before 1.1.1998, check for additional instructions with the motor manufacturer.
