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Medha Servo Drives Pvt Ltd.
MAS 696 Operator’s Manual
Gen. Voltage. These capacitors operate at the DC LINK Voltage between
600 to 3400 V DC. When the Locomotive shutdowns, these capacitors could
remain high Voltage causing severe injury or death to the operating and
maintenance personnel.
A procedure has been developed to discharge this high voltage into Dynamic
Brake Grids to prevent the possibility of Injury.
1. Before shutdown of the Locomotive, keep RUN/ISOLATE switch in
ISOLATE position and then shutdown the Locomotive. All 'BRAKING
CONTACTORS' picks up and discharge the DC LINK capacitors
through Grid resistors in one second. After 20 seconds all DC LINK
switch geares are driven to shorting position.
2. After shutdown, the Locomotive remains the COMP. CONTROL and
TURBO LUBE PUMP Circuit Breakers in ON position. These two
CB's are required to perform POST LUBRICATION for TURBO
SUPER CHARGER for 35 minutes.
3. If any disturbance for Post lubrication occurs within 35 minutes, while
cranking, Computer does not allow for cranking unless PRE-
LUBRICATION is successfully completed for 15 minutes.
2.2 Automatic Discharge
The DCL Voltage is discharged automatically, when the Locomotive operator
takes manual action to shutdown the Locomotive. There are 3 general ways
to discharge the DC LINK capacitors and other components prior to
servicing, plus a fourth method to maintain the short.
1. Reverser in Centre Position (Through Bleeder Resistors)
Each Traction Inverter has Bleeder Resistors (400 k ohms/200 W)
across the DC LINK. When the Reverser is moved from Forward or
Reverse to Centre, main Generator Excitation stops. If no further
action is taken, the Bleeder Resistors discharges the DC LINK
voltage to less than 50 Volts in approximately 50 minutes.
Although very reliable, the Bleeder Resistors do not guarantee the
discharge since the resistor could be interrupted internally or
externally.
2. Run/Isolation Switch (Through Dynamic Brake Grids)
The normal way to discharge the DC LINK capacitors is through
two Dynamic Brake Grids in parallel. When Locomotive operator
turns Isolation switch from RUN to ISOLATE (or the LCC loses the
