Inverters on Tram Cars

Originally built in the 1930s, Blackpool's familiar trams run 11 miles along the promenade to the fishing port of Fleetwood. There are over 70 tramcars in service with the Blackpool fleet and, although over 60 years old, they carry thousands of passengers each year.

Blackpool "Balloon" Cars in original form.

Power to drive the cars comes from a 550Vdc overhead supply traction which, traditionally, also has been used to supply all the ancillary power requirements such as the saloon lighting and heating, windscreen wipers, headlamps, trafficators, and saloon heating. Such an arrangement has a number of disadvantages. For example, if the power supply failed at night, the lighting system also would fail leaving passengers stranded in the dark. In addition, special expensive electrical systems and fittings have to be used - the lighting relies on five 110V filament lamps wired in series rather than the standard lamps which are powered from the now standard 24Vdc used on all modern public transport vehicles, such as diesel buses and light rail cars.

Refurbished balloon car 723 with new low voltage interior lighting, head & tail lamps, and trafficators.

In 1990, with safety standards having moved on over the past 60 years, the Blackpool Transport and the Railway inspectorate began. to scrutinize the safety of a 55OVdc supply running through a series of lights at ceiling level. It decided that a system of improved safety was required.

Preserved Tramcar 'Bolton 66'

Newton Tesla (Electric Drives) Ltd, a distributor and system integrator for Mitsubishi Electric, has devised system based on Mitsubishi A140 and A500 series inverters to feed off the 550Vdc input in the central section of the inverter, first transforming it to three-phase 415Vac. Then, instead of putting a motor on the inverter, a transformer is connected to transform and rectify the supply down to the voltages required.