Caterpillar TAURUS 70 Manual De Usuario

Turbomachinery Package Specification 

 70 Compressor Set and Mechanical Drive 

The start system provides torque to initiate engine rotation and to assist the engine to 
reach a self-sustaining speed. The start system consists of either a direct-drive AC starter 
motor driven by a solid-state variable frequency drive (VFD) or an optional pneumatic 
start system. 

The direct-drive AC (DAC) start system consists of a squirrel cage, three-phase, ac-
induction motor with a solid-state variable frequency drive (VFD). The starter motor is 
mounted directly on the gas turbine accessory drive gearbox. The VFD regulates voltage 
and frequency to the starter motor for engine rotation as commanded by the Turbotronic 
4 control system. 

To begin gas turbine rotation, the VFD initially provides low-frequency AC power to the 
starter motor. The VFD gradually increases the speed of the starter motor until the gas 
turbine reaches purging speed. When purging is completed, the control system activates 
the fuel system. The speed of the starter motor is gradually increased until the gas 
turbine reaches starter dropout speed. The VFD then deenergizes the starter motor and 
the motor clutch assembly is disengaged. 

The starter motor (Figure 9) provides high breakaway starting torque and acceleration 
from standstill to starter dropout speed. The motor is standard frame size and is 
constructed to be explosion proof and flameproof. The motor includes an integral over-
temperature protection thermostat connected to the Turbotronic 4 control system for 
hazardous area motor certification and protection. Separate cable/conduit entry points 
are provided for power connections, thermal protection wiring, and the space heater 
wiring. Starting power is transferred to the gas turbine via the reduction-drive gearbox 
and over-running clutch and shaft assembly. 

The VFD (Figure 9) is a motor speed controller that provides pulse-width modulated 
power with variable frequency and voltage to the starter motor. Controlled by the 
Turbotronic

 4 control system, the VFD regulates voltage and frequency to the starter 

motor to control engine speed from standstill to starter dropout speed. The system is 
capable of performing up to six start attempts per hour, as well as extended purge cycles 
for heat recovery unit applications and engine wash cycles. The VFD cabinet is designed 
for installation in a non-hazardous location. Electrical disconnects and overcurrent 
protection devices are not provided. 
 
 

© 2009 Solar Turbines Incorporated. All rights reserved. 

TPS70CSMD/309 

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