Induction motor generator capacitor

[jim hardy]

Wow what a slip. --- I'm 68 not 58... Guess I feel younger here . Great company has that effect.

On your drill press conversion : Did you use the electronic speed control unit from treadmill ?

 

[RonL]

Wow what a slip. --- I'm 68 not 58... Guess I feel younger here . Great company has that effect.

On your drill press conversion : Did you use the electronic speed control unit from treadmill ?

At 70+ numbers start to lose meaning:D
I just love treadmill motors:) it's so easy to use a simple speed control and full bridge rectifier, but low voltage to run slow speeds has to be very carefully protected in some way.

 

[H012]

Wow what a slip. --- I'm 68 not 58... Guess I feel younger here . Great company has that effect.

On your drill press conversion : Did you use the electronic speed control unit from treadmill ?

I did use the controller from the treadmill. There is a lot of info on the MK series controllers which most treadmills use for conversion. The treadmills I do find most have bad rollers for the belt. The motor I put on the drill press is a 2.5 Hp , more than I need really but it doesn't have to work that hard. I like using the controllers with the motor because it also controls speed by sensing load.

 

[H012]

I wanted to update everyone after a month of testing. I ventured off my original reason to do some research and testing. on different motors
First: general purpose motors are a waste of time. on any level they produce 100+ volts but no power. Now to the 1 1/2 Hp 115/220v commercial motor I originally started this thread with: I started with 2/ 40uf capacitors wired parallel into the motor capacitor leads. I loaded the
capacitors with 115 volt before starting up. When I ran the motor asynchronous It produced 110 volts but when I put a 100 watt light as a load
the light output lumens fluctuated . So as a test I started adding more capacitors 40uf at a time as I have a bunch of these. as I added more capacitors the better the output stability. I arrived at 200uf total where the sine/cosign wave was stable. 56 hertz. I next unhooked the load and turned off the generator, i wanted to see if it would self excite after sitting a day. It does! I was actually surprised. My conclusion is that although an induction motor will generate with only a small capiactor to excite it the unit will not stay generating when a load is put on it. I am no electrical engineer but it seems that enough capacitance is needed also to act as a battery am I wrong? Also the 2 5/8 hp tread mill motor.
when i hooked up to a battery the to an inverter to the same 100 watt bulb stalled the 3.5 hp briggs engine In my opinion I just need a bigger power plant. maybe a 5.5 hp. Any opinions are welcome .
. .

 

[zoki85]

That's a typical behaviour of async. generator. As you spin the machine, due to remanent magnetism in iron of the machine there will be induced small emf E₀, which will start to force current I_C0 through the connected condenser and stator winding, this current will induce higher voltage etc. This process ends when output voltage reaches magnitude E_s determined by magneto-voltage curve of the machine and the condenser current line at operating frequency (see http://gifyu.com/images/SelfExcited.png). After you excite the generator, you can hook a load to it as you did. Dependence of relative voltage drop on condenser size is very steep near nominal load point, but is much less critical for relatively light loads as shown qualitatively http://gifyu.com/images/2kw-380V-50Hz-star.png

 

[H012]

That's a typical behaviour of async. generator. As you spin the machine, due to remanent magnetism in iron of the machine there will be induced small emf E₀, which will start to force current I_C0 through the connected condenser and stator winding, this current will induce higher voltage etc. This process ends when output voltage reaches magnitude E_s determined by magneto-voltage curve of the machine and the condenser current line at operating frequency (see http://gifyu.com/images/SelfExcited.png). After you excite the generator, you can hook a load to it as you did. Dependence of relative voltage drop on condenser size is very steep near nominal load point, but is much less critical for relatively light loads as shown qualitatively http://gifyu.com/images/2kw-380V-50Hz-star.png

Great read! This makes sense.The whole reason I went to this level of testing of induction motors was to educate myself and be able to set straight 95% of the myths out there on the web that presume to say yea grab an induction motor and make a generator. From all the help you guys have offered and doing my own research it's not that cut and dried so to speak Thanks, and by the way I'm still trying to get a 3 phase
motor to test. I will update if interested.

 

[jim hardy]

Also the 2 5/8 hp tread mill motor.
when i hooked up to a battery the to an inverter to the same 100 watt bulb stalled the 3.5 hp briggs engine In my opinion I just need a bigger power plant. maybe a 5.5 hp. Any opinions are welcome .

The DC motor stalled the gas engine? That really suggests that the DC machine saw a dead short across its terminals... what's in that inverter ? Is it still working?
Have you belted the machine RPM down so that it only makes 15 volts or so?

i'm confused for now...

 

[H012]

The DC motor stalled the gas engine? That really suggests that the DC machine saw a dead short across its terminals... what's in that inverter ? Is it still working?
Have you belted the machine RPM down so that it only makes 15 volts or so?

i'm confused for now...

Sorry it took awhile to get back. My clock is different due to the fact I work nights. Anyway I did have a short, when I put the end bell back on the motor I got one of the wires pinched. luckily the inverter has a protection circuit. After fixing this every thing worked great but maintaining 15volts
is problematic when I plugged in my vacuum cleaner up [ I chose the vacuum cleaner because I wanted to see what happened under a heavier draw.] at 9 amp draw the 3.5 hp Briggs motor motor struggles to maintain constant rpm. . I need to work more on the pulley ratios to run the gas engine faster. Right now the engine is only running 1300 rpms.. It's not simple as this treadmill motor really produces a lot volts as motor rpms increase. 15volts is nothing for this DC motor to produce. Thanks for the reply.

 

[jim hardy]

Briggs uses custom springs in the governor and there's a zillion different ones (I'm thinking of the vane in airflow type governors). I can see how it'd struggle to control near idle...force on vane is quite light there.

Sounds like you're mighty close.

Sorry for my intermittency of late, am traveling and access is sketchy.

Thanks for the updates, I immensely enjoy learning from others !

Old jim

 

[H012]

Briggs uses custom springs in the governor and there's a zillion different ones (I'm thinking of the vane in airflow type governors). I can see how it'd struggle to control near idle...force on vane is quite light there.

Sounds like you're mighty close.

Sorry for my intermittency of late, am traveling and access is sketchy.

Thanks for the updates, I immensely enjoy learning from others !

Old jim

That's why I want to put a bigger pulley on the treadmill motor. That way I can increase the briggs RPM up to it's most efficient power band.
Right now at 1300 engine RPM it's under it's power band which is 2600 -3600 rpm sweet spot. according to Briggs and Stratton Tech.
Will let you know how it goes. Regards Ray

 

[H012]

This is my final update to this thread. My final conclusion is yes I achieved the voltage and amperage desired to use an induction motor as a small generator. The problem is the engine has to run to hard to overcome the magnetism's clamping effect at asynchronous speed. Using a straight up induction motor as a generator cannot and would not be fuel efficient. Companies who have designed induction generators have made specific winding inclinations and arrangement to overcome problems.
I want to thank all who shared their ideas and thoughts. H. Ray Mills