Fan Motor Won't Generate

Probably shaded pole. Try a DC motor instead, unless there's some distinct reason for variable frequency, variable voltage AC output.

Tim

-- "I've got more trophies than Wayne Gretsky and the Pope combined!" - Homer Simpson Website @

Doug

You've got my interest. Would you mind telling us what this generator is intended to be used for?? It is aparent that there is an interest in being able to pedal the stationary bike at some rate fast enough to make this induction ( squiril cage) motor be a generator. How much faster can be expected? That is, whats the maximum frequency tolerated? How much power do you anticipate being able to produce with this?

Jerry

Impedance protection means the resistance and inductance of the motor windings reduce current draw at stall so the motor doesn't draw so much current that it burns up. Impedance protection doesn't necessarily prevent the motor from being destroyed, it prevents it from causing a fire (supposedly).

Without rewinding the motor, you can't remove this impedance - it is integral with the winding.

Are you leaving the phase-shifted winding disconnected? I haven't seen any capacitor-run motors used as induction generators. (I also haven't seen any small motors used this way, and the high impedance of small motors may be why.)

I really don't know if that will make any difference. If you really want to excite the motor/generator, you might try the battery charger route with the motor RUNNING (ie. spun by the mechanical power source). If the caps are in place, and a current pulse is applied to the windings, it can't not excite the rotor. The only way it can't work is if the rotor field collapses because it can't develop enough leading current through the (AC) capacitors to maintain the field. This is a function of the capacitance and the intrinsic motor inductance and resistance. Note the guy with the 1 HP motor was reading 11 A of capacitor current!

Jon

The whole purpose of the experiment is to determine the generator efficiency and output capacity by driving the rear wheel through its motor generator, and so the front generator through the pedals, in reverse. At some point, a chain tension meter provided by Polar will be needed to measure the mechanical power delivered to the generator. Initially, it'll just be a DC motor driving an ac motor through a chain drive that happens to be part of a working recument bicycle.

One suitable load is a Dialight Hi-Flux LED module drawing only eight watts. With its LED current source going off line at 80 VAC and below, it should prevent depoling the rotor at shutdown. Other loads would have to be switched on and off line before shutdown. The LED module was donated by John Viselli at Dialight and is a great headlight; it has the right beam pattern. You would not believe how bright it is at eight watts. It's dazzling to look at.

Eventually, I would like to provide 110 VAC to an abandonded house or group of campers overnight, and also ride a century (100 miles) overnight without the use of batteries.

Why?

HMMWVs in the field deliver primary and secondary batteries and food to our troops. Each year, they make more runs with more batteries and less food. This generator and bicycle would provide troop mobility, carry loads, and eliminate battery requirements, allowing direct conversion of human power to electricity in the field. It's an unsolicited proposal under the Army's Dual-Use Technology program relating to Land Warrior and Objective Force Warrior. It's an alternative to the complicated system being developed.

Let's face it, the electrically powered bicycle just plain dies when the battery runs out. A bicycle that you energize with your efforts turns that problem on its head.

The operating voltage range of the LED current source board inside the LED lamp module is 80-135 VAC. The frequency isn't specified, but the board is a switching-type power supply.

Mobile power supply.

Entirely depends on gearing.

Tolerated by the generator or the module or what?

We'll just have to see. It's an experiment to determine the efficiency, output, and cost of this configuration. It's a reliable configuration, I think. Solid state and contactless.

Yours, Doug Goncz ( ftp://users.aol.com/DGoncz/incoming ) Student member SAE for one year. I love: Dona, Jeff, Kim, Mom, Neelix, Tasha, and Teri, alphabetically. I drive: A double-step Thunderbolt with 657% range.

30,000 joules are available when the capattery is charged. That should be more than enough. The Linday Publications "Alternator Secrets" said to hit it while it was running with 12 VDC from the car battery through a momentary NO switch.

This sounds hopeful.

I got the impression from InductionGenerator.html that if the load went off line at 80 VAC it would leave the generator in a condition to self start. I have not acheived self start but haven't achieved operation either. I think I can eventually figure this out. Get it running with the load online, then shut down and see if it will restart

Is any reader predicting low efficiency due to the impedance and resistance of the windings? What rewind would be best for generator operation. The motor runs well below capacity when used to drive the transmission for transmission tuneups.

The ESGE twin kickstand and wooden kickstand leg brace with shallow holes to receive the legs raises the rear wheel off the floor so the transmission can run. With the AC motor running, the operator can shift through the gears at constant crank speed. The operator can sit in the seat to to do this, but not pedal. Pedaling puts dynamic loads on the kickstand. I wore one out. Removing the pedals reduces the dynamic loads from motor powered pedal rotation. These loads are minor compared to dynamic leg loads.

For generator operation I use the 35 ohm main winding.

Does a regular induction motor self-start? Yes. Is this a capacitor-run induction motor? Yes. Does the capacitor provide extra starting torque? I think so. How does an induction motor start? I'm not sure.

All these question are answered in my EET 350 text. I have my EET 350 text. I dropped out but was doing well at the time I was having socialization problems with staff, not faculty. ODU didn't broadcast the first class and the instructor didn't show up for the second class. I like to get what I pay for. I like to pay for what I get, too.

I have two reports in an envelope with a letter of transmittal addressed to ODU's Office of Disability Services. That should clear things up so I can get back to doing the work.

The reports are my vocational evaluation and my psychiatric evaluation.

Did you know I have 97th percentile finger dexterity and a GAF of something like 35? It's frustrating to be so capable and at the same time limited by other factors.

I threw the manual dexterity test because the tester said to do it in a mindless fashion. That's proven to work. I was afraid performance on that test would tip the DRS I was ready for a mindless job so I did it a different way, a mindful way, my way.

Yours, Doug Goncz ( ftp://users.aol.com/DGoncz/incoming ) Student member SAE for one year. I love: Dona, Jeff, Kim, Mom, Neelix, Tasha, and Teri, alphabetically. I drive: A double-step Thunderbolt with 657% range.

Doug

You do have complex and interesting project. As I understand, you have decided to do *this* part of your testing by spinning a single phase 60 Hz motor fast enough to make it generate power. And this motor (used as an AC generator) will be spun thru some gearing, by a DC motor. My knowledge of motors and generators is limited. But, I would have thought the choice of a motor to be used as a generator would sacrifice alot of 'overall efficiency'. But, I guess you have reason for wanting the motor you have chosen. I'm now curious to know why the motor was preferable to using an alternator to generate power. An alternator will supply power at any RPM while an induction motor needs to always be spun faster than its "synchronous" RPM.

I have no dificulty beleiving the brightness of the LED you are working with. Don Foreman has been good enough to share his understanding of LEDs and their power requirements.

Jerry

This is not an alternator in the sense they are talking about I think.

But only momentarily.

Not a chance. [Might occasionally happen but it wont be because the load went off at voltage x, no mater what x is]

3 phase yes, single phase NO, not without a start winding and a capacitor.

What I understand that you are trying to do is INHERENTLY flawed. Among other things you are trying to get an over damped system to resonate.

If any thing, you need to take your motor, and parallel it with the capacitance that results in minimum current flow to the system under load, as a starting point. But an impedance protected motor is going to have WAY too high losses to get any real output.

jk

30 kJ should be enough to pull the conductor bars out of the rotor, if you could actually deliver that much energy to the stator windings. Fortunately, their resistance prevents you from doing this.

Yes, I think I might be able to predict that. What is the actual DC resistance of the motor's main winding?

Gasp! 35 Ohms? Are you sure you got a good connection? That is a LOT of resistance, and certainly explains some of your problems. You may simply not be able to get the required phase angle with resistance like that to excite the rotor. No matter how many thousands of uF you put on it, the phase angle is going to be dominated by that R.

Assuming this is a 120 V motor, you couldn't get more than an amp or so out of it, but that's about where the impedance protection wants it to be. It might be pretty tough to rewind such a motor, but if you can cram enough copper wire in there to bring the resistance down, then you would be in better shape. That sounds might desperate.

The rotating magnetic field "washes over" the stationary rotor. The moving magnetic field excites current in the shorting bars in a manner like a transformer. The coupling of the rotating stator field and the induced rotor field drags the rotor along. It speeds up until the relative movement of the rotating stator field to the individual shorting bars becomes so slow that the induced rotor field decreases due to the slight resistance of the shorting bars. With the rotor field in sync with the stator field, the back-EMF bucks most of the applied excitation of the stator, and the starting surge decreases to the stady-state current draw. It is interesting to note that induction motors show some of the interesting characteristics of synchronous alternators. If you vary the (rotor) field strength of a synchronous alternator, the stator current phase relationship changes. You can get the current to be lagging (inductive) with a reduced field, just like an induction motor. Or, you can get it to be leading (capacitive) by increasing field strength. I think that is the real function of the capacitors in an induction alternator, to force the current phase to become leading, and thereby increase rotor field strength. But, changing the load on an induction motor changes the rotor field strength by changing the slip rate, and thereby changes the phase of the current draw.

Jon

OK.

35 ohms +- 2.5 ohms ratty clip leads that need to be soldered.

For generation experiments so far, yes. See below.

I do stuff like that. I am a very patient, persistent man. Let's not worry about efficiency now. I want to get the donated 8 W white LED signal lamp online as a headlight. I connect it. It goes off line at

80 VAC. I don't mind pedaling hard to get it online. First online, then efficiently.

Understood.

Now, how about I series a 6V 15 W incandescent bulb with the motor operating as a motor with run cap and both windings, then apply load to the motor by shifting gears? I predict the illumination of the bulb will change, brighter with each increase in load.

Now, the same but with chain off the side of the small chainwheel, no mechanical load other than motor bearings, pinion to chain, chain to chainwheel, and bottom bracket friction.

At operating rpm, I will follow the pedal with my hand and apply various mechanical power loads by hand. I predict the lamp will increase in brightness when I load the motor by hand, decrease when I assist the motor, null at non-zero brightness due to losses in the motor when I overcome the listed frictions by hand, and then _increase_ due to slip when I carefully drive the motor forward by hand, overcoming bearing resistance, indicating generation, which can blow a breaker or expose personnel on line work to shock. I supppose

So perhaps it'd be safer if I used my sine wave inverter, and did the experiment locally. I do not know if you can back drive a sine wave inverter. It cost $180. I have a DC ammeter than can indicate reduced power consumtion in the inverter.

Or I could use an isolation transformer. I dont' have an AC ammeter and can get one for $17. I don't have an isolation transformer, either.

I think this is a good first step, installing the telltale bulb in series. It's easy and I have the bulb already. It's cheap and goes together with clip leads. Cheap ones that need soldering.

ftp://users.aol.com/DGoncz/Bicycle/ACMotorGenerator

One jpg and two avi's.

Doug