Turbine Package Operators Manual
Chapter 1
Turbine Package System Overview
1-23
Starting System
The turbine is started with a hydraulic transmission system driving through an overrunning clutch
assembly on the auxiliary gearbox. The turbine rotor is accelerated to a speed at which fuel may
be introduced into the combustion system and ignited to provide self-sustained acceleration, up
to the normal operating speed.
General Description
The hydraulic start system comprises of an AC motor driven hydrostatic pump and boost pump
mounted on the turbine underbase to drive the gearbox mounted hydrostatic starter motor. The
hydraulic starter motor connects through a high-speed overrunning clutch and associated gearing
in the gearbox to the turbine rotor assembly.
The pump and motor displacements are controlled to provide the correct system acceleration.
On achieving a successful turbine start and at a pre-set speed, power to the AC motor is
removed and the system deactivated.
Turbine lubricating oil is used for the closed loop hydraulic circuit. Make-up oil is drawn from the
lubricating oil tank to provide cooling.
During the hydraulic starter motor run up, the position of the variable geometry inlet guide vanes
and stator blades are adjusted by the variable geometry stator actuator to optimize aerodynamic
conditions for the starting cycle.
Prior to ignition, the turbine compressor interstage bleed valve is used to bleed compressor air to
atmosphere to reduce the start-up power requirements and prevent compressor surge.
The Schematic Diagram of the Starting System is located in this Manual Volume.
AC Electric Drive Motor
The AC electric drive motor (XM3) for the start system is an induction motor with anti-
condensation heaters and thermistors for monitoring the motor winding temperatures. The
thermistors relay temperature information to the programmable controller and provide start
inhibit, and high temperature warning and shutdown signals.
Hydraulic Pump Assembly
The hydraulic pump assembly (XP5, XP9) is a variable displacement, axial piston type with pre-
set pressure cut-off control. The varying current signal from the unit control panel adjusts the
pump displacement to achieve the required control rate.
Hydraulic Motor Assembly
The variable displacement hydraulic starter motor (XM91) is fitted with a pre-set high-pressure
related volume control. This control will decrease the motor displacement thereby increasing
turbine speed as the motor differential pressure reduces.
