More generator Q's

There is a class of AC induction motor, now rarely seen, that DOES have a wound rotor and a commutator much like on a DC motor. One difference is they often have a "bracelet" in the commutator that flies out and shorts all the segments together when the motor reaches a certain speed.

A variable resistor can be put in series with the brushes to regulate torque when starting. We have an ancient merry-go-round here that has such a motor, it takes about 3 minutes to come up to synchronous speed, which would fry a standard induction motor. The operator slowly cranks out the resistor as the motor speeds up.

These were also used on streetcars, and a variety of other things that took a long time to start moving. Now, of course, a VFD would be used.

Jon

(...)

At the time, I had an exercise bicycle that used a magnetic 'reluctance brake'. There was a knob next to the handlebar yoke that I could twist to provide any amount of pedal resistance. A meter next to it indicated the number of watts I was converting. It probably wasn't terribly accurate but it was good enough for a 'ballpark' figure and interesting for a guy that is ~97% fat :)

Between 'warmup' and 'cool down', I could keep the needle above 70 W for a half hour, consistently without endangering my health.

I was very impressed when I learned that world - class bicyclists can generate over 480 (Four Hundred Eighty) watts continuously during a one hour time trial!

Dayum.

--Winston

I have a couple of 6.5 KW Onan 120/240 volt 60hz generators. They both have wound rotors and stators. One takes the power off the rotor via slip rings and the other (newer) takes the power off the stator. In this case the field,(the rotor) has dc supplied to it via slip rings. Even though there is usually enough residual magnetism to get generation going, both sets "flash" the field with some of the starting battery juice to make sure the field current builds up quickly.

Yes. I bought the Nigel Smith book mentioned in another post on this thread. I focused on the setup called "C-2C", using a 3 phase motor to produce single phase ac power. It does work. I am using a 5 hp 3 phase electric motor which is being driven by a 12 hp Briggs gasoline engine that is running at about 2200 rpm and belted to produce 60 hz at that engine speed.

Yes, The Nigel Smith book is the one to get. Also, type "induction generator" into youtube and you won't see the light of day for about a week.

Pete Stanaitis

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On a wound coil armature and a wound coil stator any residual magnetism can induce a current into one of the coils and excite the other one. With motion energy applied this can feed itself (self excite), as if the battery was there, once in motion.

Without two sets of windings this doesn't happen.

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A newer fuel injected vehicle requires enough current to run the fuel pump and the computer in addition to the coil, so you be walking now.

BobH

I wouldn't be too impressed, just yet..... :)

Here's why:

If you calc backwards from a 480 watt mechanical output, you wind up with a VO2 of 100. Keep in mind that the elite of the elite possess VO2 *MAXes* of about 95, and VO2max is a semi-instantaneous value, NOT a sustained value. I'll have to check, but I think VO2max need only be sustained for a fraction of a minute to qualify as VO2 max.

Sustained (aerobic) VO2s are usually *maybe* 80% of VO2max values. And that last 20% is almost exponential in its perceived exertion, ie, quite unsustainable. Iow, a marathon runner may win a race at 80% of his VO2max (2+hours), but if he "miscalculates", and runs at 90%, he may crap out after 1/2 hour -- or sooner.

Marathon runners are toodling along at 18-20 cals/min, while your above cyclist is calc'ing out at 34 cals/min -- which is unheard of, on a sustained basis -- at least for 150 lb. guys. 300# -- mebbe..... :)

I'll post the calcs iffin inyone is innerested, basically just conversions.

Was *your* 70 W really 70 watts? Hard to say. I can tell you that I can run for a solid hour (if you pay me), albeit not at any earth-shaking pace, but at 180# and with hills, that is some effort/expenditure.

The point being, I couldn't keep a 100 W lite bulb lit up for more than 3 minutes, a few days ago, on my cycle-generator. Now, I think I'm getting better quickly, as I haven't cycled in literally 40 years, but still, even with substantial improvement, 1/2 hour at that output is proly beyond my wherewithall -- both physical AND psychological!

Inyway, just some perspective on some of these hyooge wattage claims. A little more perspective: Some cyclists claim 2000 W peak outputs, which I might believe, over a second or two. Powerlifters have been measured at near-10,000 W instantaneous efforts, no doubt over fractions of a second, possibly milliseconds. Staggering, when you think about it.

But, what you can do for second is a *whole* lot different than what can be done for 10 secs, 1 min, 5 min, 10 min, 1 hour.

And then, of course, you have the HSN/QVC pod peeple, effervescing: Oh, Oh, OH, I just burntid 500 cals in 1/2 hour, and dint even knowed it!!!!! Not hardly, sweetheart..... If you burntid 500 cals in 1/2 hour, you likely woudn't be goin to work the next day.....

FWIW, when the Gossamer Albratross crossed the English Channel, which took 2 hours and 49 minutes, the power required in still air was said to be 0.4 hp -- about 300 W, on average. That assumed still air. Normal disturbances increase the horsepower required.

Here's a quote from a cometitive cyclist and engineer. It agrees with what I was told when I competed in road sprints, back when tires were made of cast iron :

"Most fit adults can produce 100 watts (0.134 horsepower) of mechanical power on a bicycle for a sustained period. A world-class competitive cyclist can produce up to 500 watts (0.67 horsepower) over a sustained period of time."

Of course, you'll get a lot less from a small generator. IIRC, automobile alternators are something like 60% efficient, and there is the mechanical loss involved in driving them. Permanent-magnet alternators in the same size, however, are said to be up to 90% efficient. Don't ask me.

(...)

I don't really know for sure. That's just what the instrument indicated. :)

--Winston

(...)

(...)

We would have killed for cast iron. They made *us* knap our tires from granite. :)

That is believable considering that a physically compromised middle - aged schlub managed 70 W for 30 minutes twice a week.

Stunning!

..And the often - ignored massive amount of power needed for the field winding.

Thus their use in 'n'+1 alternative energy devices:

--Winston

Oh, c'mon. Now you're exaggerating. It takes too long to knap tires from granite. There probably are some RCM members who have tried...

I think that the 60% includes the power lost by exciting the field. Again, going from memory, I think that automobile alternators are reluctance-type. They're flexible but not particularly efficient.

I hope "a sustained period" = three minutes! LOL!!!! Makes you wonder how one defines "most fit adults"....

Heh, you *could* make it foolproof/tautological by defining fit adults as those who can generate 100 W for 1/2 continuous hours.... LOL!!!

A world-class competitive cyclist

I'll believe dat s*it when I see five 100 W bulbs at full brightness for a solid hour..... :)

Previously, I managed 2:45. Just now I managed 3:30... that's minutes/seconds... LOL!!!

Now, "manage" is really context sensitive... at what point does one "quit"? With no objective blood/lab values, that's really a dicey Q for true reproducibility, so I use a kind arbitrary "pain threshhold": where I'm whining for my mommy, but not yet screaming for her....

I suspect Thurs or Fri I'll be up to 5 minutes, and mebbe 10 minutes in another week, but the point is, Goddamm, I fairly regularly run a hilly full

Now, I estimated the driveline friction at about 12 W, and mebbe the PM motor (perty old... how can I tell? cuz it's not made like s*it....) is

So the comparison issue is still a begged issue.... Who really knows WTF is up with internal losses, or even true wattage readings, eh? So how do we really compare results, over the internet with diff setups?

Funny, high efficiency motors are sposedly > 98% efficient.... 3 ph, no doubt.

I highly doubt you can tell if a 100W bulb is lit 100%. The human eye is not that sensitive to relative lighting.

Talk about using actual power measurements...LOL

I wouldn't be too impressed, just yet..... :)

Here's why:

If you calc backwards from a 480 watt mechanical output, you wind up with a VO2 of 100. Keep in mind that the elite of the elite possess VO2 *MAXes* of about 95, and VO2max is a semi-instantaneous value, NOT a sustained value. I'll have to check, but I think VO2max need only be sustained for a fraction of a minute to qualify as VO2 max.

Sustained (aerobic) VO2s are usually *maybe* 80% of VO2max values. And that last 20% is almost exponential in its perceived exertion, ie, quite unsustainable. Iow, a marathon runner may win a race at 80% of his VO2max (2+hours), but if he "miscalculates", and runs at 90%, he may crap out after 1/2 hour -- or sooner.

Marathon runners are toodling along at 18-20 cals/min, while your above cyclist is calc'ing out at 34 cals/min -- which is unheard of, on a sustained basis -- at least for 150 lb. guys. 300# -- mebbe..... :)

I'll post the calcs iffin inyone is innerested, basically just conversions.

Was *your* 70 W really 70 watts? Hard to say. I can tell you that I can run for a solid hour (if you pay me), albeit not at any earth-shaking pace, but at 180# and with hills, that is some effort/expenditure.

The point being, I couldn't keep a 100 W lite bulb lit up for more than 3 minutes, a few days ago, on my cycle-generator. Now, I think I'm getting better quickly, as I haven't cycled in literally 40 years, but still, even with substantial improvement, 1/2 hour at that output is proly beyond my wherewithall -- both physical AND psychological!

Inyway, just some perspective on some of these hyooge wattage claims. A little more perspective: Some cyclists claim 2000 W peak outputs, which I might believe, over a second or two. Powerlifters have been measured at near-10,000 W instantaneous efforts, no doubt over fractions of a second, possibly milliseconds. Staggering, when you think about it.

But, what you can do for second is a *whole* lot different than what can be done for 10 secs, 1 min, 5 min, 10 min, 1 hour.

And then, of course, you have the HSN/QVC pod peeple, effervescing: Oh, Oh, OH, I just burntid 500 cals in 1/2 hour, and dint even knowed it!!!!! Not hardly, sweetheart..... If you burntid 500 cals in 1/2 hour, you likely woudn't be goin to work the next day.....

Probably much more accurate then an estimate of a 100W bulb brightness.

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Existential Angst wrote: Was *your* 70 W really 70 watts? Hard to say.

(...)

Busted. Curses!

Doubtlessly.

I see where Bosch are touting their new 70% efficient 'smart' alternator that allows digital control so that field current can be turned off during acceleration and cranked up during braking, boosting engine efficiency by as much as 3%. Smart Indeed!

--Winston

First, not an informed statement, as most fitness mfr's don't really care what a watt even is, never mind actually making accurate calibrations against a standard.

Second, there is no estimating of bulb brightness if you've got a voltmeter in front of you, and you are maintaining 120 V. This then becomes as accurate as anything, short of accurate/expensive regulators, solidstate integrators, etc.

These innovations are great to think about. Then it comes time to analyze something gone wrong...

Speaking of which, my wife's Sonata died today -- the battery died because her passenger left the door ajar at lunchtime -- and I was freaked when I went over to school to jump start it. The intrusion alarm was feebly wailing a plaintive cry, like a baby animal that was being torn apart by a raptor or something, and I couldn't get it to stop. There was just enough juice left in the battery to give out that feeble squeak, but not enough to react to the remote. When I connected the jumper cables it went into full blast -- with my head under the hood and about 18 inches from the alarm. Jesus. I didn't know I could still jump like that.

I want something I can fix with a screwdriver and a box of tools I could put under my arm. A Lotus 6 or 7 might do it. No doors, even.

Not sure about the 3660 poles per second part but pretty sure just about every windmill that is placed onto the grid does exactly this.

FWIW,

I have had the Nigel Smith book for nearly a decade now-actually bought the thing--if there is a prolonged power outage here what I do is I run a 50 hp

C2C connection gives you single phase off of a 3 phase motor, rpm ( 60 hz ) is via throttle governor and isnt particularily critical, 20% is probably okay but if in doubt use a ole telechron clock, and compare with a quartz unit..they bothe should read within a few seconds after a minute's time on line...if not, then adjust your throttle to suit.

(...)

One More Thing To Break.

Queue sympathetic headache. Ouch!

I've owned 'simple' cars.

I *will not* go back to carburetors, for I have *seen* the glory of fuel injection on a cold and dreary morning!

I *will not* return to breaker points for I have known the power of the Fat White Electronic Ignition Spark!

I *will not* slide back to the days of the bias ply tire for I have sat in awe over the Indestructible Radial Ply!

Can I get an Amen, brothers and sisters.

--Winston

Those are over-excited synchronous motors.