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Gas Turbine Startup Guide

The starting system for a gas turbine uses an induction motor and torque converter to start the turbine rotating from zero speed. The induction motor drives the torque converter through a flexible coupling. The torque converter is coupled to an accessory gear that connects to the turbine compressor shaft, providing the torque multiplication needed for startup. The starting motor, torque converter, and accessory gear work together to accelerate the turbine to its firing speed for ignition and self-sustained operation.

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78 views1 page

Gas Turbine Startup Guide

The starting system for a gas turbine uses an induction motor and torque converter to start the turbine rotating from zero speed. The induction motor drives the torque converter through a flexible coupling. The torque converter is coupled to an accessory gear that connects to the turbine compressor shaft, providing the torque multiplication needed for startup. The starting motor, torque converter, and accessory gear work together to accelerate the turbine to its firing speed for ignition and self-sustained operation.

Uploaded by

Hafiz
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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GT STARTING SYSTEM

GENERAL

Like other internal combustion engines, a gas turbine cannot produce torque at zero
speed. The starting means system is used to start the gas turbine rolling, crank it to
firing speed, and assist the fired turbine to self–sustaining speed. This is
accomplished by an induction motor starting device operating through a torque
converter coupled to the accessory gear. This arrangement provides the cranking
torque required by the turbine for startup. Also, at shutdown, this same equipment
continues to rotate the turbine rotor at slow speed for cooldown purposes.

The starting means system components and control devices are located and
mounted in the accessory compartment. The induction motor and torque converter
are mounted on a separate base structure attached to the accessory base top deck.
The starting motor drives the torque converter through a flexible coupling. The
torque converter is coupled to the accessory gear and provides the required torque
multi plication for the starting motor to drive the turbine. The primary parts of the
torque converter are the impeller driven by the input shaft, the turbine wheel which
drives the output shaft, and the stator which directs fluid from the impeller to the
turbine at the correct angle to produce the required output torque.

The function of the accessory gear in this system is to drive a number of the control
components as well as to provide the connection between the starting motor and
the gas turbine compressor. The starting means is coupled to the accessory gear #1
outboard shaft and the accessory gear #1 inboard shaft is connected to the turbine
compressor shaft flange by an oil–filled flexible coupling.

1. STARTING MOTOR (88 CR)

The starting motor 88CR is a GE Co. Custom 8000 horizontal induction motor with
anti–friction bearings. This is a 1250 horsepower, 6000 volt, 3 phase, 3000 rpm unit.

In the normal starting sequence, fluid is admitted into the torque converter hydraulic
circuit from the turbine lubrication system by energizing solenoid valve 20TU–1 at
the same time that starting motor 88CR is energized. Breakaway is achieved and the
turbine starts to rotate. The turbine begins to in crease in speed and continues to
accelerate until minimum firing speed is attained and relay 14HM picks up. When the
turbine has reached this speed, the internal geometry of the torque converter is
adjusted by torque–adjustor drive 88TM to hold firing speed constant through the
purge cycle.
The unit is held at crank speed long enough to exchange three to four times the
exhaust system volume of air. At this point, 20TU–1 is de– energized, partially
draining the torque converter, and turbine speed decreases below the 14HM drop–
out point. Once 14HM drops out, 20TU–1 again energizes and unit speed increases.
As the unit once again passes by the 14HM setpoint, fuel is admitted and ignited.
When flame is sensed, torque–adjustor drive 88TM gradually drives the vanes to the
high torque position, accelerating the unit while it is still in the warm–up cycle. In this
application, 14HM picks–up at 10% rated speed.

Readjustment of the converter geometry (torque adjustment) to the maximum

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