Methods of Starting Gas-Turbine-Generator Units [includes discussion]

Gas turbines are finding an increasing number of applications as prime movers for electrical power generating units. When combustion gas turbines are started, they are usually accelerated to approximately 20 to 25 per cent of rated speed before the combustor is fired. Further assistance during starting is usually required until the speed reaches 40 to 60 per cent of the rated value. Major components of gas-turbine-generator units may be arranged in a number of configurations. An investigation of possible types of starting devices indicates that a satisfactory arrangement consists of a 4-pole wound rotor induction motor connected to the unit at a suitable location through gearing and a disconnecting clutch. It is important that the auxiliary power supply used with induction motor starting be capable of maintaining rated voltage at the terminals of the motor.