Your question of 3 phase vs single phase power production is quite interesting when you refer to the prairie turbine site. Prairie turbine is claiming to make 5500 watts of single phase power using a Nord 7.5hp 3 phase induction motor. They claim to use one phase for voltage regulation, and one phase to generate electricity.....Up until I read that part, I was quite interested in Prairie Turbine's goal of creating a low cost, anyone can build, simple turbine.
If you look at their site, you see the reason they use a three phase rather than single phase motor is because it was readily available surplus from an industrial crane.
However, as they can only use one of the 3 phases to cogenerate power at a single phase household, they will only be able to extract about 2.5 hp which equates to about 1.7kw rather than the 5.5kw they claim in their breezy 5.5 ad.
If someone can correct me if my conclusions above are wrong, I would appreciate it. Otherwise, Prairie Turbine should be looked at as another 'snake oil' sales site.
Gary[ Parent ]
I haven't bought their plans yet, but from what I can tell you are using 2 phases. If you stop and think about it, 220vac is using 2 phases(2 sets of windings). Don't know what they mean by the 3rd phase is just voltage regulation. I would guess it is something like making a phase converter, where you just energize the 3rd phase with caps.Goose[ Parent ]
Not knowing how you arrived at your 1.7kw figure I'll explain how we arrived at ours. The method we use is to actually clamp an amp meter to the supply lines to the motor and measure the current flowing in the circuit. Then we use the formula: P= IV to arrive at the power being produced. When Breezy 5.5 is max'd out (actually when our turbine begins to limit the torque applied to the motor shaft), we measure 23 amps flowing in the circuit. Using the formula above we simply multiply 23amps X 240volts = 5520 watts (maybe we should call it "Breezy 5.52").
The power produced by the motor has much more to do with the turbine driving it then the size of the motor (easy guys, I'm still talking about asynchronous generation here). If you connect a smaller motor to Breezy's turbine, a 5 hp for example, you would be over driving the motor and probably burn it up shortly (regardless of what the motor data plate says). This is so much a fact with wind power that you can almost determine the power capabilities of a wind turbine by simply looking turbine it's self. When comparing Breezy 5.5 to other types of turbines consider that Breezy's turbine is turning (and pretty much held) at speed around 120 RPM and is a four blade turbine over 18` in diameter.
Gary, I see that you have referred to our web site as "should be looked at as another snake oil site". I must say that I find that remark quite offensive. And as for myself I would be quite sure of my facts before making such a comment especially if I were as ignorant of the principles of this type of generator as you would lead us to believe you are by your statements.
In contrast we have done our research and also relied on the research of others to present this turbine and the plans for it. But you don't have to believe me. In 1974 at the Technical Institute of Vaasa in Finland a study of how "squirrel cage" 3-phase motors excited and driven as generators behave unexpectedly under different wiring and load configurations. I believe some of the results of that study may still be available at: http://www.saunalahti.fi/elepal/moottori/gener_e.html. Also on a Danish website I have found an excellent description of the principles of asynchronous generation, you may want to take a look at this: http://www.windpower.org/en/tour/wtrb/async.htm .
Since I believe in the phrase "put up or shut up" I would like to extend an invitation to anyone wishing to see and measure the output of our turbine for themselves. We're located in central Kansas 20 miles south of Abilene. My only request is that you call first so that we can schedule a time. If you can't make it yourself and have a friend or relative nearby, we'd be happy to show them too. You may find our contact information and a phone number at: http://www.prairieturbines.com www.prairieturbines.com[ Parent ]
