Frequently asked questions
Learn more about gas turbine generators
What is a turbine generator?
Let’s break it down: Generators are a key component in producing power. Through powerful rotation called “torque”, they convert the mechanical energy from a turbine into electrical energy. Some sources of mechanical energy are:
Generators are everywhere around you, and help keep homes, businesses, vehicles, and more running by providing almost all of the power for electric power grids.
Gas generator vs gas turbine: How do turbines play a part?
The megawatt (MW) output of a power plant generator corresponds to the size of the energy load produced by its turbine. To understand how it ultimately powers the energy grid, here are a few factors to consider:
- The turbine and rotor create rotating inertia to improve grid stability.
- Generators convert the mechanical output of a turbine into electrical power.
- Power plants take that produced power and then transmit it into the grid.
Turbines can be powered solely by—or blends of—gas, steam, air, and even hydrogen.
What’s the science and technology behind it all?
The process is called electromagnetic induction:
- A rotor (AKA field) is an electromagnet made possible by DC electricity flowing through copper rotor coils wound into a solid steel forging—this produces a magnetic field.
- A stator is a stationary magnetized steel core wound with copper stator coils AKA stator bars.
- Rotating magnetic flux produces voltage on stationary generator stator coils, then driving electrons in the copper to move, AKA electricity.
- Simply put, you could look at a generator as an “electron pump”.
Today, this mechanical energy also comes from renewable sources like solar, wind, and hydro power.
What factors contribute to gas generator efficiency?
Many variables are considered for power-output needs, but insulation and temperature control drive a generator’s capacity to freely flow electrons through copper. For every generator, the basic equation is E = BLV:
B = magnetic flux density
L = length
V = velocity
E = voltage
The length and diameter of the rotor and stator core and the number of copper coils are examples of variables that impact E = BLV.
Moving electrons through a conductor creates heat as a biproduct, but over time, heat reduces the electrical insulation capability that holds voltage in. Copper is the most common conductor because it’s cost-effective and has low electrical resistance, which cuts the amount of heat generated. As a result, electrical insulation is a major factor in generator cost and ability.
- As copper atoms are tightly packed, “free electrons” flow easily, and the generator runs smoothly at the right temperature.
- Internal heat is managed with the right cooling systems that balance cost and efficiency.
- Temperature matters because of electrical insulation (keeping insulation at a certain temperature prevents insulation from degrading, adding service life to the unit).
- Ultimately, cooling and insulation keep thermal energy in check, protecting power transmission to the grid.
Why use hydrogen cooling instead of air?
Regulating heat inside the generator can be done with air, water, hydrogen (H2), or a blend of H2 and H2O. While hydrogen is the most abundant element in the universe, the simple answer is it’s a better temperature controller than the others. As a pressurized gas (at 30 psi), hydrogen is:
- seven times better than air at removing heat
- able to reduce partial discharges inside the generator
- far less power-consuming for circulation and heat removal, due to its low density
Hydrogen-cooled generators require fewer materials, so units can be smaller, more efficient, and more cost-effective in the certain output ranges. Hydrogen allows you to have a smaller, less expensive generator for a given output capacity.
How do generators support different power plant configurations?
Selecting the right generator for your plant can have many implications. “Power trains” connect your turbines and generators in ways that fit individual footprints.
- Multi-shaft power trains are the traditional configuration, with the turbine tied to one generator and a steam turbine tied to another generator.
- In the last few decades, single-shaft power train configurations have condensed plant footprints by connecting the gas and steam turbines to the same generator.
- Excitation systems (brushless or static) provide DC current to the rotating field, regulating the generator.
- Static exciters use a stationary power supply for faster grid response, but its the carbon brushes require maintenance.
- Brush exciters use rotating power supplies with no brush maintenance but have a slower grid response.
- With the growth of renewables, fossil plants are called on to provide grid stability—and synchronous condensers allow generators to run without a turbine to do so.
What kind of upgrades improve the abilities of a generator?
Generators are the workhorses of energy production. But the amount of punishment they take can be reduced—while simultaneously modernizing them. GE is experienced in upgrades that lower the impact of:
- intense vibrations that can erode and crack insulation
- partial electrical discharges that damage armatures
- thermo-mechanical expansion of structural metals
- dust, sand, and other environmental particles
- accelerated component aging
Newer parts and refurbished ones can be integrated into older units, extending performance and service life.
How long do generators last? Do they stay efficient forever?
Any number of a generator’s complex parts can be affected by wear, mis-operation, synchronizing errors, excitation loss, unbalanced armatures, and more. If a generator loses efficacy, a domino effect of power loss will follow. Compare it to a car that just needs the latest parts to keep running strong. Efficiency improvements on the following can elongate generator life and simply help it run better:
- sealing rings to keep oil in and impurities out
- hydrogen pressure and hydrogen purity
- bearings for powertrain dynamics
- ultrasonic level sensors
Stator rewinds and rotor rewinds bring electrical insulation back to peak performance.
How can we connect the dots?
Upkept and upgraded generators help power plants keep their uptime, meaning we can all access the energy we need for work, play, and life. After decades of learning from its fleets of generators and turbines around the world, GE knows the importance of generator health.
With our experts pushing technologies to new capability, our local maintenance and repair field services, and our dedication to understanding our customers, the generators the world depends on are in careful hands.
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