Your description above indicates to me that your looking for something that can not be easily done. Every generator control I have ever dealt with has the ability to increase speed as the load increases. Since your doing this manually I see problems. Have you considered the frequency issue as well? As load increases and the speed stays the same voltage and frequency would fall.
Hi
Please can somebody tell me the easiest way to control the voltage output of induction generator.
The generator is three phase 11 kW, excitet by capacitor bank of 240 µF; as a prime mover a tractor of 30 HP has been used. The speed of the generator can manually be adjusted, but when done, then the speed is more or less constant.
The problem is that the output voltage depends greatly on the induction generator speed and load. For a given capacitor value, self-excitation can only be achieved and maintained under certain load and speed combinations. The machine demagnetizes and stops generating either when the speed falls bellow, or the load rises beyond certain values.
So plese can somebody help me solve this problem. I would like to build voltage regulator for IG that maintains stabile voltage regardless of load and speed value.
I have looked for this topic on the internet, but i found only very complicated solutions which included voltage source inverters, and digital controllers based on a Pentium PC. I dont have anything against voltage source inverters or something similar, but hooking up a PC to control the voltage output is a bit to much.
Any ideas would be greatly appreciated; the simpler the better, even if the voltage regulation itself is not 100% accurate, as long as i can avoid demagnetization and regulate the output voltage.
Thanks.
Hi Silvek,
Controlling the output voltage of an induction generator is not easy. In a regular alternator, the speed of the prime mover is kept constant to maintain a fixed frequency and the output voltage is adjusted by changing the alternator's field current which changes the strength of the magnetic field. You can't do this with an induction generator.
I do know a way to control the output voltage, but it isn't the best solution. First, as with a regular alternator you want to keep the prime mover's speed constant to maintain a constant frequency. Next, you want to fool the induction generator into thinking that it has a constant load no matter what the actual load is. The way to do it is called load diversion regulation or shunt regulation. The way it works is a large resistive load (like say an electric hot water heater) is connected to the generator using something that can vary the amount of power. SCRs can be used for this. The regulator senses output voltage. If it's too high more of the generator's output power is sent to the load. If the voltage is too low less power is sent to the load.
This type of regulator can be made with basic analog control components like op amps. With some SCR's and a large resistive load you can easily control 11 KW. Shunt regulation can also react quickly to load changes, but there are some problems. First, any power you are not using is sent to the load - which is terribly inefficient unless you are usually running near full load most of the time. The resistive load converts everything not being used to heat. Great if you need a lot of hot water or you wanted to heat a construction site anyway. Not so great if things are already too hot where you are running this generator. Also, what you use for a resistive load must be reliable - if not a sudden loss of load will cause the voltage to shoot up and damage anything connected to it. So regular light bulbs that burn out are not a good idea.
This type of regulator is often used on small hydrogenerators. So if you want more info try doing a google search on small scale hydro power and load diversion / shunt regulator.
Hope this helps, Big John
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