CAT Titan 250 - Manual (Page 19)

Turbomachinery Package Specification Titan 250 Generator Set
6.2.2 Variable Frequency Drive
The VFD (Figure 7) 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.
6.2.3 Power Wiring
The start system (Figure 8) requires customer-furnished, three-phase AC input.
Additional three-phase AC power wiring is required to connect the VFD to the starter
motors. A start contactor is not required for VFD operation. A customer-furnished fused
disconnect at the VFD input is recommended. Optional motor space heater wiring is
available.
Figure 8. Typical Direct-Drive AC Start System
6.3 Backup Slow Rotation System
The Titan 250 package is equipped with a DC powered turning gear system (Figure 9) to
ensure low speed rotation of the turbine as backup for the DAC starter motor in the event
of loss of AC power to the package. The system engages the decelerating turbine at low
speed and maintains rotation for a specified time.
Figure 9. Turning Gear Assembly
© 2008 Solar Turbines Incorporated. All rights reserved. TPS250GS/908 - Preliminary
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