The B-series trains are a class of electric multiple unit built by Downer Rail in Maryborough, Queensland for Transperth between 2004 and 2019.

[5]: 116 In each set, IGBT inverters power eight AC traction motors distributed along the three cars, providing a 66% motorised unit.

In May 2002, a $437 million contract for the construction of the initial 31 three car B-series trains and the Nowergup depot was awarded to EDI Rail–Bombardier Transportation Joint Venture.

[7] The trains were specifically optimised for the higher possible speeds and greater station spacing on the newer Joondalup and Mandurah lines: contemporaneous planning documents expected that all-stops services on the older Fremantle, Armadale, and Midland lines would likely lead to overheating problems with the propulsion and braking systems.

[citation needed] In December 2006, the government signed another contract, worth $160 million, with EDI Rail–Bombardier Transportation Joint Venture for 15 more three car B-series trains to be used on the Joondalup and Mandurah lines.

[citation needed] In May 2011, the government announced 15 more three car B-series trains worth $164 million would be ordered to cater for the extension of the Joondalup line to Butler, and a general increase in capacity on the network.