Grid Tie and Induction Motors

[jwxr7]

Sorry I'm kinda geeked about trying this . A simpler take on the bike test set-up; You could leave the tire on a road bike in a stationary stand, and put some kind of 2.7" wheel on a 6 pole motor and mount it to run against the tire. You should be able to begin overrunnig it by pedaling around 10 mph. Now you just need to be able to detect the change in current direction and magnitude to check your results.

[csrmel]

this is right up my alley. i am facinated with power and electricity. ive been known to spend 6 hours, 12 hours, even days at a time researching one subject. my latest facination is with synchronus condensors. id love to build one, but plans on the internet are sketchy and i doubt i could do it.

dont use a ceiling fan motor or any other small motor. most of them are not good for generating power. they are shaded pole motors and not good for this. by not good means i wasnt even able to make one generate power. i got a shaded pole motor out of a box fan, applied come capacitors to it and spin it up with a powre drille. it wouldnt generate power no matter what i did. ven briefly energysing it with 110 while it was spinning wouldnt make it work.

you need a squirrel cage induction motor. squirrel cage are easy to generate power from.

you spin a squirrel cage motor at about 5% over its rated rpm, add an appropriate sized running capacitor, and BAM it generates power at a TRUE sine wave. the frequency is dependant on the rpm's, as is the voltage. you use the capacitor size to set the voltage.

good motor for generating power are continous duty motors, like that found on air compressor, water pumps, maybe a washing machine motor, but fans, etc are no good.

i have a bunch of squirrel cage motors, i collect them for enegry expirements. my best expirements are this. anyone want one? ill sell some at a good price as i have more than i could ever use.

induction motor driving another. the driven motor produces power. 1/2hp driving motor, and 1/3 hp driven motor. i even have a pair of electrical outlets wires up to it. this was my own proof of concept, and it works. i used a couple of pulleys with one being slightly bigger than the other to overdrive the driven motor.

5hp lawnmower motor driving a 3 phase 330v 1/2 hp induction motor. i converted the 3 phase motor to putput single phase 120v clean sine wave power. and it works good as a low wattage generator for powering lights and other resistive power loads.

the one real problem with all induction motors such as the squirrel cages i use, they do not work good for reactive power loads, at all. i can power a huge string of lights with my 3 phase generator but i cant even power a jig saw or box fan. induction motors are only good at true power loads, not reactive power.

[skewbe]

Originally Posted by csrmel

...dont use a ceiling fan motor or any other small motor. most of them are not good for generating power. they are shaded pole motors...

Good tip, any ideas on likely appliances to find a squirrel cage motor in?

[csrmel]

air compressor, waterpump, maybe a washing machine spinner motor. perhaps a dryer spinner motor. an industrial type fan usually come with squirrel cage motors. but things like ceiling fans are almost awalys shaded pole. box fans, blenders, hair dryers, etc are all shaded pole. pretty much any motor under 1/4hp is a shaded pole. there are awalys exceptions though.

find an junk waterpump like a sprinkler pump. they can come with upto 1 or 2hp motors. these make excellent generators. they are also super easy to fix with bearings and stuff readily available.

an easy way to tell is to look at the armature. it looks like a squirrel cage.

the BEST motor to use could be a generator head off a gas generator that has blown the gas motor. this type of head can power reactive loads, resistive loads, pretty much anything you throw at it.

it has been said that any motor can be a generator, and any generator can be a motor, but i never had luck with shaded pole. and to top it of shaded pole are very inefficent. so even if you got one to generate power, chances are its going to be a very inefficent setup. and expirements like this count on every last watt of efficency you can extract.

[jwxr7]

Originally Posted by skewbe

Good tip, any ideas on likely appliances to find a squirrel cage motor in?

I typed too slow.
most washers and dryers have split phase or capacitor start induction motors. The washers may have multiple speeds too, same with furnace blowers. Some high performance fans use capacitors on their motors for star/run windings, they don't need a centrifugal switch because the second phase created with the capacitor circuit stays on. dish washer pump motors and pool/spa pump motors should work (most are probably 2 pole 3600 rpm machines though).

I remember years ago playing with a 3 phase motor at work and running it off single phase and connecting a cap between one of those leads and the unused wire (don't remember exactly how I did it). The motor would run but I don't remember if it would self start. The whole point was to see if I could get 3 phase out of the same motor. It worked, I could start a normally wired 3 phase motor off of the other motor that was running as a rotary phase converter. I didn't run it long or load the 2nd motor down so I don't know how well it would work in the long run. I thought it was cool , bring 3 phase to your garage.

[trebuchet03]

Thanks csrmel!

That kind of experience is exactly what I need - both getting me excited and dashing my hopes in one post You pretty much listed all of the motors I have available for free I'll have to seek out alternatives

Do you know of any squirrel motors that are rated less than 1hp? Less than 1/2hp even?

What about a power drill motor?

[jwxr7]

an easy way to tell is to look at the armature. it looks like a squirrel cage.

Most shaded pole motors have a rotor like most other induction machines. They just use a modified pole that has a copper shorting ring to provide a phase shift to get the rotor turning. It is still an induction motor with shorting bars running the length of the rotor ("squirrel cage"). http://en.wikipedia.org/wiki/Shaded-pole_motor
btw The motors in blenders are typically universal motors with brushes and commutators, same with vacuum cleaners, hand drills skill saws etc and other devices needing high rpms. These are not induction motors and will not work the same way as the O.P. brought up.

[trebuchet03]

Originally Posted by jwxr7

btw The motors in blenders are typically universal motors with brushes and commutators, same with vacuum cleaners, hand drills skill saws etc and other devices needing high rpms. These are not induction motors and will not work the same way as the O.P. brought up.

Oh duh... now that you mention it -- I knew that.... Perhaps it's time for a trip to the surplus store

[JanGeo]

You can save yourself a lot of time and effort and energy loss by powering the devices you want to power with DC power directly i.e. a laptop likes about 20 volts DC into the power plug in the laptop - voltages vary, some only take 15 volts and they are a bit flexable in voltage too. It is better to just feed the DC directly into the laptop than to invert it to AC and run it through the power pack which wastes 20% converting from AC to DC. If you want to setup a generator then get a bigger motor instead of a small motor because it will be more efficient and will not have the shaded poles. Anything that runs at the multiple of 60 would be a good motor. The idea is to have the same number of field poles as there are rotor poles so there is no slipping and the core material should be straight not rotated from one end to another (shaded). Typically these are capacitor or induction start motors containing a secondary winding and a starting switch. A 3 phase motor should also work perfectly if you just use one phase since they are equal poled stator and rotor. As for getting them up to speed simply put a few series connected light bulbs inbetween the generator and the AC grid and spin the generator motor until the bulbs stay dark (indicating an in phase condition) then close the switch across the bulbs.

[GasSavers_Ryland]

according to a friend of mine who installs wind turbines for a living, some of the large scale turbines work simaler to what it sounds like you are talking about, with an air speed indicator to tell the generator that the wind speed is fast enough to start the feild windings in the generator, the generator then spins at a consistant speed no matter the wind speed, producing a perfectly matched sine wave.