Maintaining Contact:

Maintaining good contact between the pantograph atop the LRV and the catenary contact wire keeps electricity flowing continuously to the train’s motors and other electrical systems

Converter:

The 750-volt direct current in the contact wire is tapped by the pantograph and converted to a three-phase alternating current feeding two propulsion units so the train can continue to run if one fails.

Power Line Support:

A pulley and weight system keeps the copper catenary contact wire from sagging as it expands and contracts during Charlotte’s seasonal weather changes.

Power:

Each LRV has (2) 350 horsepower electrical motors located at each end of the LRV. These motors and the 750 volts of direct current in the overhanging catenary contact wire are needed to move the 44 tons of metal and about 16 tons of passengers for both acceleration and braking.

Braking System:

Four braking systems are engaged sequentially to ensure the trains do not become runaways. Below is the sequence in which the brakes are engaged:

• Regenerative Braking:

  First, electric motors slow the vehicle down by changing operating modes. The train’s momentum produces electricity, much of which is fed back into the overhead contact wire. If the overhead contact wire is not receptive, the electrical energy produced during braking is burnt off as heat called Resistive Braking.

• Disc Brakes:

  If needed, disc brakes kick in to supplement the electric braking.

• Sand Spray System:

  If the wheels begin to slide, sand is sprayed onto the track to add traction.

• Magnetic Brakes:

  The final brake to be used in emergencies is a long, powerful electromagnet that automatically lowers between the wheel contact to the rail.

Communication:

Each LRV is assigned a unique radio signal that identifies it.

• Receivers on the track pick up these signals to control intersection signals, signal stations, crossing arms, etc.
• The central control room located at the South Boulevard Light Rail Facility on South Boulevard uses the receivers to track the location of trains along the line.

Environmental Design Features:

Siemens (LRT vehicle maker) engineered design elements in its cars to enhance operation under conditions in Charlotte.

• Ice Cutter:

  A serrated brass strip installed on the pantograph scrapes off ice buildup on power lines to ensure good contact between the pantograph and power lines.

• HVAC:

  A robust system of units to deal with the humid conditions in Charlotte.

• Door Thresholds (8):

  Sloped doorways drain precipitation away from passengers and doorways.

Leveling the train with the platform:

The leveling system keeps the floor within 3/8 inch of the platform even as tons of passenger weight fluctuates. Suspension adjusts so the floor of the LRT car remains level.

Turning Volts Into Movement

LYNX light rail trains are high-tech machines powered by electric motors that are lighter and accelerate faster than diesel engines and are emissions-free.

1. Direct current (DC) is collected from the catenary contact wire by the pantograph.
2. The electricity moves through a high-speed circuit breaker to a three-phase alternating current (AC).
3. The operator controls the speed and braking of the train from the cab console.
4. The AC moves throughout the train and to each 350-horsepower motor (two per car).

During braking, the traction motors located in the wheel assembly produce energy and feed it back to the catenary system for use by other LRV trains.