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Medha Servo Drives Pvt Ltd.
MAS 696 Operator’s Manual
Main Alternator slip rings. CA produces 3 phase 45-230 V AC supply to
excite Main Alternator field through SCR Assembly and Power fed to the
Radiator Fans 1 & 2, Inertial Blower motor and Traction Inverter Blowers.
1.2 Major Features of MAS 696 System
Major Features of the System in operation point of view are explained
hereafter.
1.2.1 DYNAMIC BRAKE
Dynamic Brake is an electrical braking method used to regulate the speed of
the Locomotive by translating the Kinetic Energy in the Traction Motors into
Electric Energy. This Mechanical rotating energy is converted to Electrical
Power by using Traction Motors as electrical Generators. The power
generated by these Traction Motors are applied to the Grid Resistors, which
dissipate the generated power in the form of heat into the atmosphere, there
by reducing the speed of the train.
Re-generation operation of AC Induction Machine is not so easy to explain.
To examine the entire Braking process, consider first a DC Machine in a
Generating mode. In this case a stationary magnetic field is established in
the stator of the Motor. The momentum of the Train causes the Motor to Turn.
As the motor turns, the Armature cuts through the stationary magnetic field
in the stator. This cutting generates a current flow in the Armature which is
dissipated through Grid resistors.
On the DC Machines four power cables are run to the Motor, two are
connected to the field and two to the Armature. The cabling that runs to the
Grid Resistors makes a connection with the Armature. For Motoring
operation, armature cables and field cables are connected in series and
across the generator. During Dynamic Brake, Filed cables are connected
across the generator and armature cables are connected to the grid resistors
to dissipate the generated energy in the form of heat to the atmosphere.
In the AC Machines only three cables are connected to the Motor. These
cables supply 3 phase AC source needed by Motors both in Power and
Dynamic Brake mode. For more braking effort the Inverters supply more
power to the field. So power must always flow into the Motor to excite the field
(regardless of operation mode).
Power is multiplied by two components, Voltage and Current. The direction
of power flow depends on the relationship between Voltage and Current with
