Something completely different:
- Thread starter rattus
- Start date
- Status
crossman
Senior Member
- Location
- Southeast Texas
A wild guess would be mechanical governors and clutches?
Did they produce DC and then use an inverter?
Did they produce DC and then use an inverter?
Alternators
Alternators
Alternator output frequency is determined by the speed of rotation and the number of poles in the motor. The generator is "synchronous", the rotor field is fed DC from a small DC generator on the shaft end with brushes and slip rings. The rotor field is not induced with 'slip'.
I'm guessing you knew this.
Throttling was probably mechanical > gating the water flow, adjusted so the generator slightly leads the grid. I have no idea what was used to modulate voltage output
Alternators
Alternator output frequency is determined by the speed of rotation and the number of poles in the motor. The generator is "synchronous", the rotor field is fed DC from a small DC generator on the shaft end with brushes and slip rings. The rotor field is not induced with 'slip'.
I'm guessing you knew this.
Throttling was probably mechanical > gating the water flow, adjusted so the generator slightly leads the grid. I have no idea what was used to modulate voltage output
I think a simplified explanation is the following: The water flow through the turbines is controlled by wicket gates which are used to vary the rpm and therefore frequency of the output voltage. Once the generator is running near synchronous speed, it is synchronized (connected to the grid). The wicket gates are opening slightly further to provide real power to the grid which is a function of power angle. This opening does not change frequcny of output since they generator is connected to the grid. The reactive power is controlled by varying the dc field current on the rotor.
zbang
Senior Member
- Location
- Roughly 5346 miles from Earls Court
I've had the opportunity to tour Hoover Dam's power house. IIRC, the governors are a mass of individual coil (three in a wye) three-phase motors, galvanometers, and hydralics, but alas I don't have any photos. It is fun to watch the gate position meter (a 270deg movement) wiggle back and forth over a 30 or 40 degree angle as the system adjusts.
BTW, I do recall that the fields are something like 250VDC at around 1200 amps. Somewhere I have a photo of the nameplate on a generator housing.
BTW, I do recall that the fields are something like 250VDC at around 1200 amps. Somewhere I have a photo of the nameplate on a generator housing.
mivey
Senior Member
Mechanical type shown here:
http://www.usbr.gov/power/data/fist/fist2_3/vol2-3.pdf
http://www.usbr.gov/power/data/fist/fist2_3/vol2-3.pdf
whillis
Member
- Location
- Vancouver, BC
I had the opportunity to wander around and ask questions at the Revelstoke dam generating station 10 or so years ago. They told me that when they need to bring a turbine on line they run it like a synchronous motor to bring it up to speed and synchronize it. Once it's synchronized they open the gates and let the water in to start generation.
They also said that one or more turbines will be often be running without any water hours before peak demand times approach both to provide inertial reserve to damp switching transients and so they can quickly bring additional capacity on line.
They also said that one or more turbines will be often be running without any water hours before peak demand times approach both to provide inertial reserve to damp switching transients and so they can quickly bring additional capacity on line.
K8MHZ
Senior Member
- Occupation
- Electrician
A similar start up technique is used with land based gas turbines. A computer controls the engines to keep the generators synchronized.
dbuckley
Senior Member
- Location
- Canterbury, New Zealand
The root of the OP's question is frequency - I read a book a little while agao, Electrical Timekeeping by Frank Hope-Jones, and in there was pictured a clock used at power stations. Well, it was two clocks, a mechanical clock and an electric clock, and it was the job of the power system operators to make the clocks stay together. This requirements persists to this day; the long term frequency accuracy of any civilised country's electrical grid is astounding.
Other than that, I learned (from this very forum) that there are only two controls for syncronised alternators that matter, one is field strength, and the other is throttle. In the case of a hydro generator, then the throttle is the gates that determine the flow of water to the turbine.
Edited to add - further to what Colin noted above - at the Dinorwig pumped storage power plant in Wales, they go from offload to nearly 2GW of on-line generation in about 15 seconds. This plant is designed to cope with millions of households putting their electric kettles on at the advert breaks in soap operas. What they do there is spin the turbines up as motors, and then open the floodgates (literally) at just the right moment...
Other than that, I learned (from this very forum) that there are only two controls for syncronised alternators that matter, one is field strength, and the other is throttle. In the case of a hydro generator, then the throttle is the gates that determine the flow of water to the turbine.
Edited to add - further to what Colin noted above - at the Dinorwig pumped storage power plant in Wales, they go from offload to nearly 2GW of on-line generation in about 15 seconds. This plant is designed to cope with millions of households putting their electric kettles on at the advert breaks in soap operas. What they do there is spin the turbines up as motors, and then open the floodgates (literally) at just the right moment...
Last edited:
- Status