Power
was originally taken at 6,600V 3 phase AC and feed to 3 substations,
where rotary converters, supplied by English Electric were used to
convert the power to 440V DC. The rotary converters were replaced in
1960 with more economic mercury-arc rectifiers. In 1981 the
National Grid took over the power supply, this was bought in at 11,000V
AC and is feed to 5 substations along the line. The Mercury-arc
rectifiers were replaced with GEC air-cooled silicon diode rectifiers,
this reduced power loss and did away with large cooling fans.
The driverless trains take power from a center rail, which runs at
440 volts DC in the main tunnels, which allows the trains to travel of
speeds, of up to 40 mph. The station section operates at 150 volts,
which allows the trains to travel at approx. 7 mph. One of the running rails
is connected to earth, thus acting as a earth for the traction current and
also track circuits. The other rail is divided into short sections,
connected with isolators. When the wheels of a train bridge the sections
an electric relay is operated which removes the power from the last
section of track. The power is not restored to that section until the
train clears the section that it has just entered. This gives a dead
section of track to the rear of each train. The train brakes are held
off by electromagnets, so when a train hits a dead section of track the
train brakes are automatically applied.
Hear
the Relays operating whilst David Kemp,
tour guide, describes operation.
WAV File. 616 Kb. MP3 File 234 Kb.
When
the Railway was first opened, it was controlled from control
panels located in the inter-platform tunnels at the stations.
These panels allowed trains to be shunted in the station, or routed
straight on to the next station. The switch panels were mechanically and
electrically interlocked. Outside each station is a short dead section which
brings each train to a halt. If they can be admitted, the line
controller could operate a receiving lever controlling a camshaft motor which
closes three relays progressively bringing into use three different voltages
to control the trains rate of approach. The first relay energizes the
dead section at normal line voltage, 440 volts and sets the train going,
the second relay reduces the voltage to 206 volts, so slowing up the
train without the use of brakes (remember the 1 in 20 gradient) and the
third relay reduces the voltage to 150 volts which brings the train into
the station at 8 miles an hour. On entering the station, the train
rides into a "dead section" and the brakes are automatically
applied by springs.
1993
saw the installation of a £750,000 computer to take over control of the
system from one central point. The Vaughan computer directly interfaces
with the existing control system. The computer system was bought into
operation section by section, this allowed the system to carry on
operating as normal during the installation. Each station has its
own computer, interfaced to the existing relay system.
The computer can
control the progress of each train on the system automatically. If
needed the line controller can take control of any part of the system,
and reroute trains as needed.
Check out the Track
plans of the
railway, as it was after the new station was built at Rathbone Place. Many of
the passing loops, and sets of points have been removed from various parts of
the system.
Power
was originally taken at 6,600V 3 phase AC and feed to 3 substations,
where rotary converters, supplied by English Electric were used to
convert the power to 440V DC. The rotary converters were replaced in
1960 with more economic mercury-arc rectifiers. In 1981 the
National Grid took over the power supply, this was bought in at 11,000V
AC and is feed to 5 substations along the line. The Mercury-arc
rectifiers were replaced with GEC air-cooled silicon diode rectifiers,
this reduced power loss and did away with large cooling fans.
When
the Railway was first opened, it was controlled from control
panels located in the inter-platform tunnels at the stations.
These panels allowed trains to be shunted in the station, or routed
straight on to the next station. The switch panels were mechanically and
electrically interlocked. Outside each station is a short dead section which
brings each train to a halt. If they can be admitted, the line
controller could operate a receiving lever controlling a camshaft motor which
closes three relays progressively bringing into use three different voltages
to control the trains rate of approach. The first relay energizes the
dead section at normal line voltage, 440 volts and sets the train going,
the second relay reduces the voltage to 206 volts, so slowing up the
train without the use of brakes (remember the 1 in 20 gradient) and the
third relay reduces the voltage to 150 volts which brings the train into
the station at 8 miles an hour. On entering the station, the train
rides into a "dead section" and the brakes are automatically
applied by springs.
1993
saw the installation of a £750,000 computer to take over control of the
system from one central point. The Vaughan computer directly interfaces
with the existing control system. The computer system was bought into
operation section by section, this allowed the system to carry on
operating as normal during the installation. Each station has its
own computer, interfaced to the existing relay system.