speed senser for induction motor

[eraser1]

what can i use as a speed senser on an induction motor to switch a relay on and off depending on the speed of the motor, this is to connect the motor to the grid and use it as a generator

[thefinis]

While an induction motor grid tied can be used it is something that is full of problems.

Here is a link to a thread that talks about doing just this. Seems like it had a link to a discussion with the details of a speed sensor

http://www.fieldlines.com/story/2006/7/2/8853/36057

Finis

[vawtman]

Not a good idea for the homebrewer.My opnion.

 Best would be to feed a inverter.I think because once the load is applied(its tied)it will treat the grid has a battery does to other machines and drag it down and unless its oversised and can change pitch on the blades to maintain speed it seems to me that there would be constant battle there.

Ive had thoughts on this but seems alot is wasted trying to achieve this.

I think an inverter can handle wider ranges.Not sure though.

 My .01$ worth.

[tdmack]

(Written for Eraser1's post last week.....had broken comment link)

Eraser1

There is nothing complicated or complex about grid connecting an induction motor/generator whether powered by wind, hydro, or steam. A key item is of course the "speed sensor. For an excellent example one could use a PIC chip to control the relays with a hall device situated at the motor shaft to feed pulses into the PIC which are in turn used to detect rpm.

In the case of a wind turbine you'll also need a "powered released" brake, gear reduction, and a stall regulated turbine rotor. A properly chosen motor will include the first two and the latter is a very simple rotor which is designed to have an increase in torque output up to a given wind speed and then plateau.

This is of course a basic explanation and but really not meant to sound overly simple.

The real beauty of this set-up is that you can grab some real horse power right off the shelf. We do sell most all these components but you can get them locally as well. As for our PIC controller, one could substitute with a small PLC which are becoming quite affordable.

Tim