7
Chapter 1 - System Overview
Medha Servo Drives Pvt Ltd.
contacts with the help of DC Motor controlled by Locomotive Control
Computer (LCC) which is housed in Electrical Control Cabinet 1 (ECC#1).
Traction Control Cabinet (TCC) consists of six Traction Computers, 6 DCL
switch gears, 6 IGBT based Inverters, DC link Capacitors and Crow bar
circuit. Based on the Inputs received from Locomotive Computer and
analogue feedbacks from Traction motors, Traction computer converts the
DC power into 3 phase AC power required to the traction motors. LCC
receives the operator request as digital inputs and analog signal from
different sensors and sends request to the traction computer for converting
required amount of Power during Motoring and Dynamic Braking modes. The
term TCC refers to an Electrical System that converts DC power into 3 phase
AC power during motoring and 3 phase AC power into DC power during
dynamic brake. The terms Invert and Convert are interchangeable in this
locomotive during Power Mode and Dynamic Brake Mode.
The Traction Motors are 3 phase AC Induction Motors. The 3 phase AC
power from Inverters are fed to the Traction Motors mounted on the Trucks,
Each Traction Motor is geared with a pair of Wheels with the gear ratio 17:90
(MAC loco) for Goods Service and 17:77 (PAC loco) for Passenger service.
The Traction Motors once again convert the Electrical power into Mechanical
power to provide high starting Torque required for Locomotive service. These
are explained in detail in later chapters.
1.1.1 Auxiliary Generator
The Auxiliary Generator (Aux. Gen.) Is driven by the Engine gear train at
three times of engine speed. Its field is controlled by LCC through AG PWM.
AC power from Aux.Gen. is supplied to an external 3 phase Full wave
rectifier in the Battery Charging Assembly. There it is converted to 74 volts
DC power for Companion Alternator excitation, control system operation and
Locomotive Battery charging. The Aux. Gen. also supplies 74 volts DC power
for Fuel Pump Motor, Turbo lube oil Pump circuits, Locomotive lighting and
other miscellaneous equipments.
1.1.2 Companion Alternator
The Companion Alternator (CA) is coupled directly to the Traction Alternator
within the Main Generator housing. The Companion Alternator is physically
connected to the Main Gen. assembly but electrically independent to the
Traction Alternator. Companion Alternator has 16 field poles on the same
rotor back of Main Gen. field poles. The rotating CA field poles receiving low
voltage current from Aux. Gen. through a pair of slip rings are adjacent to the
