Man VTA, Project Manual, Page: 29 / 42

6 Operation
6.1 Putting into Operation
The adjustable turbine nozzle ring is supplied as specified. Minimum and
maximum nozzle ring cross sections are factory-defined by means of
mechanical stops.
To connect servomotors to the control and servo cabinet, the system must
be de-energized in order to prevent destruction of the servomotor encoder.
Once the power supply has been switched on, the system is operational.
Following integration of the VTA control system into the engine control sys-
tem, calibration of the frequency inverter/controller (reference run) is required.
There is a special function for this in the VTA control system. Referencing is
carried out in the factory.
NOTE Adjustment of the turbine nozzle ring during engine operation is
carried out fully automatically by the programmed VTA control
system.
6.2 VTA – Adjustment Ranges and Adjustment Speeds
Turbocharger TCA55 TCA66 TCA77 TCA88
Cross section change speed (mean value) in
cm²/s 29.6 34.4 Not speci-
fied
Not speci-
fied
Table 16: VTA turbine nozzle ring – adjustment speeds
6S46MC-C engine TCA55 turbocharger
Ratio AD
max
/ AD
min
2) 1.2
Duration of adjustment of specified adjustment range
in s
2.5
2)
AD = narrowest flow cross section of the turbine nozzle ring
Table 17: Adjustment values of a VTA turbine nozzle ring on a 6S46MC-C engine
6.3 Emergency Operation on Failure of the VTA Adjusting Device
The purpose of emergency operation is to bring the turbocharger with VTA to
a safe operating state in the case of a mechanical or electronic defect in
order to assure operation of the engine.
The torque of both servomotors serves as the main criterion for automatic
shutdown of the VTA. Incipient mechanical damage can be detected in its
initial stage by means of continuous torque monitoring and prevented by
shutting down the VTA early.
In this case, a fault signal is output to the engine control system. The
response to the fault signal is implemented in the engine control system.
VTA on 2-stroke engine
VTA on 4-stroke engine
Example:
VTA on 6S46MC-C engine
Mechanical defect
2013-12-04 - de
6 Operation
6.3 Emergency Operation on Failure of the VTA Adjusting Device
MAN Diesel & Turbo 6
EN-US
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