Development of compact alternator rectifier for diesel-electric locomotives

In Diesel-Electrical locomotives, power can be transferred from diesel engine to motors mounted on axle of locomotive by either DC generator or Alternator-Rectifier combination. The latter arrangement is preferred due to better efficiency and less maintenance. In the design of rectifier for diesel locomotive, special care is to be taken to withstand multidirectional vibration, air contamination with much, dust, oil fumes etc. and taxing atmospheric conditions. Many design concepts have been employed by locomotive manufacturers, such as stand-alone panel, alternator-mounted, with capsule devices, with flat base devices, with independent cooling air and with tapping traction motors cooling air and with tapping traction motors cooling air. The proposed design employs flat base diodes with fuses, is mounted on alternator and uses cooling air of alternator. Rectifier is capable of delivering rated power even with isolation of one diode. Mounting on alternator releases floor space in locomotive, a scarce commodity on diesel locomotive, besides utilizing cooling air produced by fan of alternator, hence no separate arrangement of cooling air is needed. The rectifier has been designed, manufactured and tested successfully. Test results are even better than the design values. More than 40 such rectifiers are working on diesel-electric locomotives in India and abroad.