Grid Tie and Induction Motors

[SVOboy]

So you're going to power your place by stationary bike?

[trebuchet03]

Originally Posted by SVOboy

So you're going to power your place by stationary bike?

Not entirely Perhaps enough to run my laptop - in ideal situations, that + a few light bulbs

[jwxr7]

^^ wait, that high velocity fan... Is that a typical $10-$20 box fan - shaded pole? Or a more "industrial" fan (the type with metal blades and a metal cowl)?

It's not a typical cheap box fan, it's similar to this one. http://www.lakewoodeng.com/fanpgs/hv18c.html
It isn't a shaded pole, it has a capacitor on it.

Another tip if you shop for a motor on-line; if they say it is an induction motor and it can be reversed then it is most likely NOT a shaded pole motor, and should be a good candidate.

[jwxr7]

That reversible tip I posted earlier got me thinking about ceiling fan motors. I have a spare lying around that I decided to tear apart. It is a capacitor run induction motor (not shaded pole)with maybe 14 or 16 poles . It is a common style using 5 blades and 3 speed settings. I think most will be this way that have a reverse switch. It is an inside out motor, so it looks pretty interesting. I plan on testing for output today, but am not expecting many watts since the unit is only rated 85 watts input max.

Edit; Just tested. Sorry, don't get too excited, it didn't back feed. I tried all three speed settings and even spun it way up over 800 rpms and it didn't even lower the input wattage by very much.

[csrmel]

just because a motor has a capacitor does not mean its not a shaded pole. i have seen plenty of shaded pole capacitor run motors. one which is a squirrel cage fan out of a microwave. another is a table fan, my box fan has a running cap and its a shaded pole too.
the main reason shaded poles are used is because they are cheap to produce compared to a good induction motor. but shaded poles are energy inefficient, have low starting torque, and just plain bad for generating electricity.

if you guys want a good induction motor, i have 3 sitting here im not doing anything with. a 1/3hp delta 1725rpm, a 1/2 ge 1725.
if you add a capacitor to the output of these motors and run them a little over 1725, they generate electricity. you can use the rpm's to vary the voltage but this also varies the frequency.
the best way to set an induction motor up for generator power is to put a capacitor on it, get it generator power and then adjust the rpm of the motor to get 60hz. then adjust the UF of the capacitor to get about 125v out of it.
i can ship them for $9 to anywhere in the usa, and i only ask $15 for each motor.

the odd thing about induction motors is that they generate amps weither you use them or not. i think the power bounces between the cap and the motor windings. so if you set a motor up on a excersize bike and have nothing plugged into it, the load is the same compared to running a set of lights.

[jwxr7]

just because a motor has a capacitor does not mean its not a shaded pole.

That may be true, but I've examined the stator poles on the ones I've been testing to be sure of weather they are shaded or not. I'm simply testing different types and sizes of induction motors for suitabilty for grid tied generation.

csrmel, It sounds like you are talking about using induction motors as a stand alone generator. That isn't the ultimate goal in this thread. A typical induction motor will not generate power without the grid current in the stator (without modification), and that is a good thing for grid tied apps. It is a safety benefit if the power goes out, nobody wants power sent back into the grid under these conditions.

someone at otherpower.com said this

Using grid tied induction generator you will have automatic voltage and frequency regulation, just need to vary the slip to produce the amount of power you need. For Shutdown, Induction generator have automatic shutdown if the grid exciting current is out, to be safe you need some gateways of breakers and overload relays. Induction generators have a characteritics of failed safe grid connection. If you need help, please contact me.

I just tested a 1/3hp 4 pole wound rotor induction motor and it worked very well as a grid tied induction generator. I was easily able to get 500 watts back into the grid. This motor has the ability to be adjustable in it's rotor circuit so it may be even better with tweaking. I removed grid voltage from this motor while testing and the output went to zero. This looks like the motor I will integrate into something for grid tie.

[csrmel]

an induction motor works equally well as a standalone generator or a grid tied generator. either one requires exactly the same wiring job and the same over speed characteristic and you still need to actually power the generator via some other means than electrical (bike, lawnmower, etc)

so i dont see why you want to distinguish the 2, because there really is no difference. perhaps nobody understands that. ill respectfully bow out of the topic and leave you geniuses to you're work.

[jwxr7]

Yeah, I'll leave this thread alone now. I get all into a subject like this which involves things I work with everyday so I act like a know-it-all but I don't know it all. I mean to help but I should just tell about what I've had work and focus less on other details, sorry guys.

I'm sorry csrmel . I wasn't trying to say you were wrong but I guess it seems that way when I reread it. It is true that an induction motor will work as a stand alone generator as long as it has exitation current of some sort, and you are right about adding a capacitance across the output to enable self excitation. I guess I considered adding a capacitor as a modification in my above post which it really isn't. I was only trying to say that without this modification they work safely grid tied which I think is what we're after.