Class 30 locomotives of New Zealand Railways

New Zealand Railways Corporation operates a predominantly freight service between Wellington and Auckland over what is known as the North Island Main Trunk (NIMT). Electrification of the central portion of the NIMT has been considered on a number of occasions to improve line capacity. In 1981 the New Zealand Government gave approval to electrify 411 km of the NIMT between Palmerston North and Hamilton. A 25 kV AC overhead supply system was chosen and 22 Class 30, 3 MW, Bo-Bo-Bo locomotives were purchased. The authors describe the equipment layout, performance, electrical equipment, and traction control strategy