Does the output frequency of an induction generator vary with rpm?
Does the output frequency of an induction generator vary with rpm?
(OP)
Does the output frequency of an induction generator vary with rpm?
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Does the output frequency of an induction generator vary with rpm?
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RE: Does the output frequency of an induction generator vary with rpm?
RE: Does the output frequency of an induction generator vary with rpm?
I have a poor understanding of AC systems in general. 3 phase, induction, power factor and rotating magnetic fields make my brain hurt.
RE: Does the output frequency of an induction generator vary with rpm?
If you are connected to a large grid, the grid establishes synchronous frequency.
Generator speed will be slightly higher than sync speed (by an amount slip*sync speed)
Slip is proportional to real load (for a given terminal voltage and a given grid frequency).
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(2B)+(2B)' ?
RE: Does the output frequency of an induction generator vary with rpm?
RE: Does the output frequency of an induction generator vary with rpm?
Gunnar Englund
www.gke.org
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Half full - Half empty? I don't mind. It's what in it that counts.
RE: Does the output frequency of an induction generator vary with rpm?
RE: Does the output frequency of an induction generator vary with rpm?
http://inside.mines.edu/~msimoes/documents/pap10.p...
Mike L.
RE: Does the output frequency of an induction generator vary with rpm?
RE: Does the output frequency of an induction generator vary with rpm?
http://www.labvolt.com/downloads/download/86376_f0...
RE: Does the output frequency of an induction generator vary with rpm?
At speeds near synchronous speed, the relationship between torque and slip is very nearly linear. Let's take a common 4-pole motor for 60Hz operation listed at 1740rpm at rated torque. 1740rpm is 29rps, or 58Hz on a 4-pole motor. The slip is 2Hz at this rated torque. If the load torque were increased to 150% of rated, the motor would decelerate, increasing the slip and therefore the generated torque, until the slip hit 3Hz at 1710rpm and the motor generated 150% of rated torque, balancing the load torque. Similarly, if the load torque were reduced to half of rated, the motor would accelerate, decreasing the slip until it reached 1 Hz at a speed of 1770 rpm, generating only 50% of rated torque to balance the load.
This relationship continues on the other "side" of synchronous speed. If the machine is mechanically driven with a torque equivalent to the rated torque, it will have a -2Hz slip frequency, so the electrical frequency on the rotor will be 62Hz and the mechanical speed will be 1860rpm. Driven mechanically at 150% of rated torque, it will get to -3Hz slip and 1890rpm. Or at 50% of rated, the slip will be -1Hz, and 1830rpm.
In all of these cases, it will be taking power from the grid (for the motoring cases below synchronous speed) or putting power into the grid (for the generating cases above synchronous speed) at 60Hz. All of this assumes that the grid is "big" (to use the technical term) compared to the machine, so the action of the machine has minimal effect on the frequency of the grid.
Curt Wilson
Delta Tau Data Systems
RE: Does the output frequency of an induction generator vary with rpm?
While a normal induction motor works well as a generator directly connected to the grid with several types of prime mover, wind power is not on that list.
Well, with an over-sized turbine and shedding a lot of wind most of the time it may work with wind but at that point it makes more sense to use a type of generation that can handle more peak power.
Bill
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"Why not the best?"
Jimmy Carter
RE: Does the output frequency of an induction generator vary with rpm?
RE: Does the output frequency of an induction generator vary with rpm?
Get the point? Trying to "buy back" the purchase price of the turbine based on the saved power is unlikely. By the way, you WILL have to purchase the transformers and wiring and controllers all sized for that 100 Kwatt potential output, because on some days some of the time, it will be producing 100%. Until the wind goes too high, then it shuts down to prevent damage.
RE: Does the output frequency of an induction generator vary with rpm?
The Endurance does indeed fall into a category called "fixed speed" wind turbines, in that power is only generated when the blades are spinning in a relatively narrow RPM range. As turbines get larger, this actually less of a problem than you might think. That's because the efficiency of the blades have a relationship of their own to the wind speed, based on the "tip speed ratio" (TSR). This broadens the range of wind speeds for which the blades remain effective. Additionally, wind is highly volatile itself, and constantly matching blade speed to wind speed in any efficient way is a complicated procedure. Instead, the larger wind turbines actually rely on their mass to smooth the volatility, and then pitch the blades according to the average wind speed to optimise the TSR. That's why even the large DFIG based turbines are effectively fixed speed wind turbines.
I say all this as the developer and proponent of a "variable speed" small wind turbine based on an induction generator. There are definitely some advantages to be had, particularly at the smaller end of town but there are some significant challenges too.
RE: Does the output frequency of an induction generator vary with rpm?
For small wind machines, even an inefficient generator can be used to produced power in a managable range. And I say inefficient to mean not optominized for any factor other than first cost.
At the distribution level, it dosen't matter to the power company as long as the power quality to the other customers is not impacted, and the total generation on the feeder does not impact the operation of protective equipment, and personal safety issues are addressed. The billing people and adminstration are a different matter, and will change from company to company.
RE: Does the output frequency of an induction generator vary with rpm?
Speed = governor control.
Power = voltage control.
Voltage control is achieved by altering the excitation.
RE: Does the output frequency of an induction generator vary with rpm?
It's an induction generator.