GE 151X1202YE08PP08 Panel of the case / Structural component

151X1202YE08PP08    Panel of the case / Structural component

Torque vs. Speed Curves

A typical gas turbine torque-speed curve shown below, shows the turbine load torque

(unfired torque and fired torque) and the generator output torque (motor torque). The

acceleration torque is determined by the difference between the generator output

torque and the turbine load torque. The acceleration torque and the inertia of the

shaft determine the acceleration rate. As the accelerating torque becomes larger the

turbine is accelerated faster. The Static Starter adjusts the generator output torque to

have the turbine follow the startup sequence.

Notice that the turbine is accelerated in an unfired mode up to approximately 25%

speed and is fired at 15% speed. The period between these two points is the

wobulating purge and the coast down. At 90% speed the torque produced by the

turbine is sufficient to accelerate to top speed and the Static Starter is disabled.

Generator Voltage vs. Speed Curve

The following figure shows a typical generator starting voltage profile. During

startup the generator field current is controlled so that the generator stator flux does

not exceed allowable limits. The Static Starter output voltage increases linearly from

0 to its rated value of 4160 V ac as the speed increases from near 0 to 18 Hz (for 7F

turbine applications), providing constant volts/hertz (flux) on the generator.  Above

18 Hz, the Static Starter output voltage is held constant and volts/hertz falls off

inversely with speed.

System Configurations

The starting system configuration should be chosen to provide the best optimization

of cost and starting availability. The following sections illustrate the various starting

system configurations that are available and define the benefits associated with each.

One Starter for One Turbine

The one-on-one configuration

has the advantage of

simplicity. There are no

provisions for redundancy

with this system.

In this starting system configuration, one Static Starter is responsible for starting

only one turbine-generator set. This is the simplest system, both in terms of physical

layout and implementation. There is a single starting bus associated with the one

Static Starter. The generator has an 89SS motor operated switch that is used to

connect the generator stator to the starting bus. The one-line diagram for this one-on

one configuration is shown in the following diagram.

One Starter for Multiple Turbines

In this starting system configuration, one Static Starter is responsible for starting

two, three or four turbine-generator sets. There is a single starting bus associated

with the one Static Starter. Each generator has an 89SS motor operated switch that is

used to connect the generator stator to the starting bus. The one-on-four

configuration is shown in the following diagram.