1. Prospective current is greater that max prospective current declared for selected Altivar. Be sure that prospective current at Altivar input is below the value specified in dedicated Altivar catalog. For example max prospective current for ATV630D37N4 is 50kA.
2. Drive supplied to DC bus. If the drive is supplied to DC bus, be sure that charging current is limited. For small drives (below 18kW for 400V drives) there is pre-charging resistor inside, so current is limited. But drives above 18kW requires either external pre-charging circuit or charging current to be limited by DC supply.
3. Drive's DC is used to supply other drives to their DC bus. Be sure that other drives, connected to subjected drive will not consume more current than input rectifier of subjected drive can withstand.
4. DC bus capacitors needs reforming after long storage, see dedicated maintenance manual. As an example extracted page from ATV630 service manual enclosed.
5. Other reason can be environmental (e.g. conductive dust), overvoltage in the network (lightning) or product wearing (e.g. internal short-circuit, capacitor failure)
