South African Class 22E
The Transnet Freight Rail Class 22E of 2015 is a South African electric locomotive. On 10 April 2015, the first Class 22E dual voltage six-axle locomotive for Transnet Freight Rail was rolled out by the CSR Zhuzhou Electric Locomotive Company in China. Manufacturers. The first forty Class 22E dual voltage 3 kV DC and 25 kV AC Co-Co locomotives for Transnet Freight Rail were built in China by Zhuzhou Electric Locomotive Company, a subsidiary of the China South Locomotive and Rolling Stock Corporation (CSR). The roll-out ceremony of the first locomotive, no. , took  place at the factory on 10 April 2015. The rest of the order for 359 locomotives are being built locally at the Koedoespoort shops of Transnet Engineering in Pretoria. The acquisition of the Class 22E forms part of the largest-ever locomotive supply contract in South African history and the single-biggest investment initiative by a South African corporation. It consists of contracts for the construction of 1,064 locomotives by four global original equipment manufacturers: The builder's plates on the Chinese-built locomotives are inscribed with the year 2015, but for an unknown reason the plate on no. 22 -041, the first of the South African-builts, is incorrectly inscribed "2014". The Class number. In the 1930s, during the steam era of the South African Railways, a heavier mainline version of the Class 21 steam locomotive, the Class 22 , was proposed, but never built. The Class 22E is therefore the first locomotive in South Africa to receive this class number. Characteristics. The locomotive body is a welded monocoque design, constructed of steel plates and profiled members. The Class 22E locomotive is virtually identical in visual appearance to the earlier Class 20E and Class 21E locomotives, but longer, with a  different wheel arrangement and a different interior layout. It has a nominal rating of . This is the second type of modern Co-Co design electric locomotive to join Transnet's fleet after the heavy-duty Class 15E, which is used on the Sishen-Saldanha (Orex) route. Both these locomotives are single cab types. Layout. The Class 22E has a single cab and a gangway along the centre of the locomotive, while the interior layout and placement of equipment is as follows, from the cab towards the rear: Dual voltage. As on the dual voltage Classes 19E, 20E and 21E, the  main electric circuit is automatically selected in either AC or DC mode based on the voltage of the overhead contact wire feeding the locomotive. To facilitate automatic trouble-free transition on the run, the locomotive is equipped with onboard voltage detectors, while the overhead wire is equipped with two wooden isolators and a length of neutral wire to separate the AC and DC feeds. The neutral section is connected to the rails which serve as the return conductor on electrified lines. The transition process requires that the locomotive should automatically be switched off before it reaches the isolators and the  unpowered overhead wire section, and automatically be restarted after exiting from under the unpowered wire. This is done by a pair of track magnets, one on either side of the neutral overhead wire and spaced apart. The two magnets are mounted with their polarities reversed in relation to each other and they activate a magnetic relay located behind the cowcatcher of the locomotive to do the switching off and restarting. Pantographs. Transnet Freight Rail insisted that the locomotive must be designed in such a way that the pantograph contact shoe centres are directly above the bogie pivot centres, as was  done on the Class 7E and Class 7E2, Series 1 and Series 2, and again on the Classes 20E and 21E. The reason is to reduce the possibility of pantograph hookups on catenary in sharp curves, such as in turnouts, as a result of sideways movement of the pantograph in relation to the overhead wire.