Load testing a 3 phase stator

Reloadron

Joined Jan 15, 2015
7,890
Rich, not a real big deal but you may want to give some thought to:
Stator rated output: 180W (so 60W / phase)
180 Watts @14v dc is 12.8 amps @ 1.08 Ohms (assuming 100% efficiency)
With a 3 phase system I believe things go a little like:
Watts = (V * I * Power Factor * 1.732
For a resistive load the Power Factor will be 1.0 but there is also the constant in there of 1.732 and the 1.732 being the square root of 3. So the 180 Watt output is actually the Voltage * Current * 1.732.
Maybe with any luck at a bike show I can get a decent stator connector as this summer or when we finally get some warm weather I can more easily look at my own bike. Currently in the garage vacationing from snow and ice. Damn, I hate winters. First day of spring and we got another 6" of snow last night.

Ron
 

Thread Starter

Rich:-)

Joined Oct 14, 2016
61
With a 3 phase system I believe things go a little like:
Watts = (V * I * Power Factor * 1.732
For a resistive load the Power Factor will be 1.0 but there is also the constant in there of 1.732 and the 1.732 being the square root of 3. So the 180 Watt output is actually the Voltage * Current * 1.732.
Ah, ok. My AC theory sucks, I haven't touched it in so long, in fact actual electronics work (other than hobby stuff) is a distant memory.:(

So, with 14v DC output, not accounting for any losses through the R/R, the best current output will be 7.423 amps?
 

Reloadron

Joined Jan 15, 2015
7,890
Ah, ok. My AC theory sucks, I haven't touched it in so long, in fact actual electronics work (other than hobby stuff) is a distant memory.:(

So, with 14v DC output, not accounting for any losses through the R/R, the best current output will be 7.423 amps?
That would be my guess. While I never gave the alternator on my bike much thought it gets pretty interesting. I have a used parts local bike shop and may stop and see if they have a stator. Additionally as soon as it warms up I will have to take a look at my stator outputs. I would like to find a mating male connector which would make things much easier to look at.

Ron
 

Thread Starter

Rich:-)

Joined Oct 14, 2016
61
I'm starting to suspect that my stator isn't actually a 180W afterall....

Allow me to give an example.
This stator belongs to the smallest of my bikes, a 400 single. Years ago I updated the headlight to one that has twin bulbs and thus separate hi & low lamps. I then installed relays to switch them and a direct power feed (to reduce voltage drop at the bulbs). I also used a diode to hold the Low on when Hi is selected.

2x 55W bulbs shouldn't be a problem for 180W stator.
However a 55W bulb will take 4.58 amps @12volts dc so running 2 of them should be too much as it's asking for over 9 amps, I'd expect to see the voltage drop at the battery.

I have a video of a test I did, after watching it again I have listed my observations,

Battery was old but charged and showing 12.6v initially, whilst cranking this dropped to 10.5, then with the engine running (idle) 14.2 volts.
Turned on 1 headlight bulb (plus sidelight) - no change 14.2 volts across the battery.
Turned on the other bulb - it dropped to 13.1 volts (at idle).
I raised the engine revs and as the revs climbed the voltage across the battery returned to 14.0 volts, I didn't rev any higher once 14.0 was reached but it looks like it would have returned to 14.2v.

This should not be possible if the maximum current available was only 7.423 amps.

The voltage at bulbs will be higher than 12v too, I estimate 13.5 volts due to the upgraded wiring to reduce voltage drop along the loom. So the bulbs were probably taking closer to 10 amps combined, yet the voltage was still normal at the battery terminals. This could not happen if the stator was only 180 watts.

Therefore I have 2 suspicions.
1. The value quoted is the DC power available to the bike and not the stators actual rating.
2. The value quoted is BS, it's just internet hearsay.

I have looked in a workshop manual, some technical specs on marketing guff etc and I cannot find a stated rating from the manufacturer.

I looked in a Clymer manual and found the following,
Alternator
Type 3-phase AC
Output (regulated voltage) 13.5-15 volts at 5000 rpm
Wattage 200 watts at 5000 rpm


However, even if the stator is 200 watts it is still not enough to supply the 2x 55w bulbs.
 

Reloadron

Joined Jan 15, 2015
7,890
I looked in a Clymer manual and found the following,
Alternator
Type 3-phase AC
Output (regulated voltage) 13.5-15 volts at 5000 rpm
Wattage 200 watts at 5000 rpm


However, even if the stator is 200 watts it is still not enough to supply the 2x 55w bulbs.
I have always relied on the Clymer manuals as a sort of holy grail for this stuff but have to agree something is peculiar here. Something you may wish to try is placing a shunt downstream of the diode bridge and regulator. There are plenty of cheap shunts coming in from China and for basic test work they do just fine. Using for example a 50 Amp 50 mV shunt you can see exactly what you have going on. Using a shunt begin turning accessories on and looking at total current and battery voltage you should get a feel for what the alternator is doing at different loads and RPM. Part of the thinking here is if under a light to no load the alternator is delivering 15 VDC for a given RPM as the load increases eventually the voltage will begin to "fold over" or drop. When that happens the alternator is under a max load.

I have been thinking of adding a small bike in the 350 to 550 cc range. However, we just built a garage and I don't want to suggest to my wife I "need" another bike. :)

Ron
 

Thread Starter

Rich:-)

Joined Oct 14, 2016
61
Once the resistors get here (and I've mounted them on heatsinks), I can have a play and see what's what.

As for bikes, can you ever have enough?
What do you have at the moment?
I have a DRZ400E for trail riding, a DL650 V-strom for touring and a KTM 990 Superduke for... ermmm... blowing out the cobwebs.:D
 
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Reloadron

Joined Jan 15, 2015
7,890
Being an old retro type I currently ride, when it's not snowing. a 1992 Harley Electroglide. I want to get a small bike for running around. Been riding all my life going back to 19 years old and I was 68 last month. A friend has a sweet little 300 Honda Rebel and I just love riding that little bike. I finally got over 6,000 miles on the Harley which I got about a year and a half ago with 5,000 original miles. Years ago I had Honda Shadow 1100 which my first direct drive bike. I really liked that bike. With my days for motocross behind me now I like the road bikes and comfort but still want a small bike just to play with. Once we are over the garage I figure I'll start mentioning it. :)

Once you get started with the stator and loads post back what you find as I am curious how this will come together.

Ride Safe
Ron
 

Thread Starter

Rich:-)

Joined Oct 14, 2016
61
Once you get started with the stator and loads post back what you find as I am curious how this will come together.
I'm undecided whether to actually play with it or not. My initial intention was just to make the load so that I have it for the future. I would like to run some actual tests but this curiosity conflicts with the tried and tested philosophy of "if it ain't broke, don't fix it" and also could well invite "sods law" :)

I did once rig an oscilloscope up to see what was happening, and the waveform was not as expected, or should I say not as clean as I'd hoped. I then modelled it in microsim which helped me understand the output, it was the non-center tapped 3 phase generator that had thrown me.

One other thing I noted is that being in a workshop with something on bench is one thing, it's generally very calm, quiet and controlled. Fiddling with an oscilloscope that is refusing to trigger reliably whilst all the time the engine is getting hotter & hotter is quite another...:D







Maybe I'll have look around for a dead engine to play on.
 

Thread Starter

Rich:-)

Joined Oct 14, 2016
61
The Harley Electroglide looks like a proper Harley. The Rebel looks fun too, it looks like Honda have recently added the Rebel 500 to their UK line up. My Mrs loves those types of bikes, maybe as time goes on I will gravitate towards them, it's already getting hard to throw my leg over my DRZ, and I'm only 47. :)

Ride safe and good luck with getting another bike.
 

Reloadron

Joined Jan 15, 2015
7,890
it's already getting hard to throw my leg over my DRZ, and I'm only 47. :)
Tell me about it. :) I get my right leg up and slide it over the seat slowly. I think in a few years when I hit 70 the Harley will become a trike. That bike weighs about 850 lbs.

The waveform off the stator doesn't surprise me. When all is said and done it will be DC. We don't get a nice clean sine wave. I also agree, if it ain't broke don't fix it as sometimes what ain't broke when we start is broke when we finish. During winters I keep a battery tender on the bike and start it maybe once a week. I also keep an oil pan warmer on the bike. This summer I would like to add heat to the garage and insulate it.

Ron
 

shortbus

Joined Sep 30, 2009
10,050
:) I get my right leg up and slide it over the seat slowly. I think in a few years when I hit 70 the Harley will become a trike.
Been there and done that. After having 2 mild strokes I no longer ride. 3 Harleys sitting in the garage, 1957 FLH,1958 FLH and a 1989 FLHTC. I got the chance to have a ride in a Polaris Slingshot not as the driver but passenger, what a trip! Now if I can just convince myself to spend the money on one, at 70.
https://en.wikipedia.org/wiki/Polaris_Slingshot
 
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