Assume the generator is loaded and operating in a steady state. If the peak-to-peak or rms value of the stator current changes in magnitude then its corresponding change in magneto-motive force (mmf) will try to change the air-gap flux by armature reaction. Relatively slow changes will allow the change in
Year: 2013
The rotating field in the air gap of a synchronous machine is generally considered to be free of space harmonics, when the basic operation of the machine is being considered. In an actual machine there are space harmonics present in the air gap, more in salient pole machines than a
The stator, also called the armature, carries the three-phase AC winding. The rotor, also called the field, carries the DC excitation or field winding. The field winding therefore rotates at the shaft speed and sets up the main magnetic flux in the machine. The fundamental magnetic action between the stator
The theoretical operation of synchronous generators and synchronous motors is almost the same. The main differences are the direction of stator current and the flow of power through these machines. The construction of generators and motors, of the same kW ratings, used in the oil and gas industry is very
In all power systems the requirement is that the steady state speed deviation, and hence frequency, is kept small for incremental changes in power demand, even if these power increments are quite large – 20%, for example. There are two main methods used for speed governing gas turbines, a) Droop
Gas turbines are usually started by a DC motor or an air motor. Either system is available for most turbines up to about 20 MW. Occasionally AC motors are used. Beyond 20 MW, when heavy industrial machines tend to be used, it becomes more practical to use air motors or
The electrical engineer should take full account of the site location and environmental conditions that a gas turbine generator will need to endure. These conditions can seriously affect the electrical power output that will be achievable from the machine. The starting point when considering the possible output is the ISO
The fuels usually consumed in gas turbines are either in liquid or dry gas forms and, in most cases, are hydrocarbons. In special cases non-hydrocarbon fuels may be used, but the machines may then need to be specially modified to handle the combustion temperatures and the chemical composition of the
There are basically two gas turbine driving methods, known as ‘single-shaft’ and ‘two (or twin) shaft’ drives. In a single-shaft gas turbine, all the rotating elements share a common shaft. The common elements are the air compressor, the compressor turbine and the power turbine. The power turbine drives the generator.
At the earliest practical time in a project the engineers will need to identify areas of engineering and design where interfaces are necessary. An efficient system of communication and exchange of information should be established and implemented at regular intervals. Meetings should be arranged to discuss problem areas and short-falls
