[Inductor-recorded traction motor sound] Helsinki Metro M100 (Strömberg SCR-VVVF)

This is it - the finale of the trilogy that’s called the Helsinki Metro. The M100 is the first series-produced VVVF train in the world, and Strömberg nailed it on the first try, never to make VVVF trains again, apart from a small batch of Dr 16 diesel-electric locomotives and a single prototype VL 86F locomotive for the Soviet market. Nowadays the Strömberg heritage brand is owned by ABB - which still has its VF manufacturing and development in Pitäjänmäki, Helsinki. Besides the back-then-cutting-edge technology, the train body is made entirely of aluminium by Valmet Airplane Factory in Tampere, Finland. The trains are wonderfully simple and provide a smooth ride, with a tiny jolt when braking during shifting from 15-pulse mode to 23-pulse mode. Many of the parts, including the doors, are picked from buses made during the 1970s and are wonderfully nostalgic. The train is liked by drivers, passengers and maintenance personnel alike. The M100 is renowned for the unmistakable sounds it produces when accelerating and decelerating, heard by people born in the 19th century up to the present day. The AC drives being SCR-VVVF has been confirmed from multiple sources, including a former technician of Strömberg. Unfortunately the aluminium body made the train very difficult to record. There was one spot on the floor where my inductor microphone could pick up anything besides static. The previous one was recorded with the inductor on the window and it picked up way too much additional sounds. The recording is still not perfect, but it was the best I could do. It has been amplified nearly 24 dB and a slight amount of the highest tones, mostly hiss, has been cut with an equalizer. The 10-step PWM pattern is as follows (thanks to VilMatrix): 43P - 31P - 23P - 15P - 11P - 9P - 7P - 5P - 3P - 1P Technical specifications: Top speed 100 km/h (electronically limited to 90 km/h, 80 km/h under normal operation) Weight: 63.2 tons Length: 44 200 mm Width: 3 200 mm Height: 3 600 mm Wheel arrangement: Bo’Bo Bo’Bo’ AC drives: SCR-VVVF (Strömberg Asynchronous Motor Inverter = SAMI) Motors: 4x Strömberg HXUR/E 505G2 per car, 125 kW each Input voltage 750 VDC The first VVVF train series in the world Numbered 101 - 184, prototype units 101 - 106 withdrawn from service; 39 units (19 trainsets) still in operation. Originally built 1977 - 1984 Refurbished 2004 - 2009 (Talgo Oy / Transtech) Undergoing second refurbishment 2019 - 2023 (VR FleetCare) Service life expected until 2031 Recorded from unit 141. Photo credits: :Kamppiin_liikennöivä, Helsinki City Museum Other photos by me