V-Strom Power Generation Checks - Stromtrooper Forum : Suzuki V-Strom Motorcycle Forums
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post #1 of 5 Old 02-23-2016, 11:41 PM Thread Starter
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Post V-Strom Power Generation Checks

V-Strom Power Generation Checks

This write-up is for the DC power generation system of the DL-650A, model years 2012-2016 (at least), having a 400W magneto followed by a shunt regulator. With adaptation of power and voltage levels, it can be applied to earlier DL-650 and DL-1000 bikes having a magneto and shunt regulator.

A Precaution Re DC Generator:

There is a pitfall in replacing only the rectifier/regulator or only the magneto stator if either has been damaged by the other. The rectifier diodes are individually under stress approaching what could damage them, and a short in the wrong place on the stator can result in much higher than normal current going through the diodes furthest (electrically) from the short, possibly damaging them. It is also possible that failure of one or more rectifier diodes would cause excessive stator current, damaging it. For this reason, I recommend (as does the service manual) verifying the operation of both the rectifier/regulator and the magneto when either has been implicated or replaced. These checks can be done as follows.

Magneto Check:

The magneto can be checked by first unplugging it from the regulator (at the 3-wire mated connector pair near the regulator), then measuring AC voltage between each pair among the 3 pins (on the magneto side, of course.) At 5000 RPM, each pair should measure a bit over 60 V RMS and the readings should be within a percent of each other among the pairs. A mismatch indicates shorted turns. Uniformly low voltage indicates magnet problems (or lots of shorted turns uniformly distributed among phases, which is unlikely.) Using the resistance function on a DMM from any of the 3 wires to ground (with the stator installed on the bike) should show many MegOhms. (open) The resistance across each of the 3 pairs should be no more 0.3 Ohms higher than what your meter reads with its leads pressed together hard. Those readings should be uniform for the same contact pressure between probes and pins. (Probe lead resistance and probe contact resistance tend to swamp the winding resistance being measured, so interpret readings accordingly.)

Rectifier Check:

The stock shunt regulator/rectifier can be checked for its bridge rectifier being intact as follows: Unplug both cables from the regulator. Using the diode function on your DMM [a], measure from each of the 3 pins on the 3-wire regulator input (the black wires), using the red DMM lead, to the black/red regulator output wires on the 4-wire regulator output, using the black DMM lead. All 3 readings should read as diodes. Then, using the diode function again, measure from each of the 3 pins on the 3-wire regulator input (the black wires), using the black DMM lead, to the black/white regulator output wires on the 4-wire regulator output, using the red DMM lead. All 3 readings should read as diodes. If all 6 diode tests showed a good diode reading, the rectifier part of the regulator is working.

[a. If your DMM has no diode function, measure the "resistance" of a diode using the resistance (or "Ohms" or "KOhms") function, with the red DMM lead on the anode (non-banded end) and the black DMM lead on the cathode (banded end), and note the reading. Treat readings within 25 percent of that as indicating good diodes when probed the same way. (Of course, you have to start with a good diode for this work-around to work. A new 1N4001 diode from RadioShack will do.) ]

Regulator Shunt Check:

Checking the regulator/rectifier regulation function is harder. Start by unplugging and reconnecting its 4-wire connector a few times to reduce contact resistance (which can throw off the following diagnostics, or even cause the appearance of a weak charging system.)

For what appears to be a weak charging system, temporarily remove the headlight connectors and turn off any customized loads. If this allows the battery voltage to begin rising, with the engine running at idle speed (about 1300 RPM), the shunt regulator is not malfunctioning short.

Charge Done Level Regulator Check:

If battery voltage (as measured at the battery terminals) exceeds 14.8 VDC at any time when the charging system is running, the regulator is bad. It should be immediately replaced (or the bike parked or the regulator output unplugged) as this fault will damage the battery and could create a hazard.

If the battery voltage does not reach 13.6 VDC after the post-start recharge has had a chance to complete [b], either the magneto is failing to supply enough current to power bike loads and charge the battery, or the regulator is reducing controlled power flow at an incorrect voltage level. (This is why the magneto check should be done too; these cases are hard to distinguish otherwise.) If the magneto diagnostic absolves the magneto, regulator output contact resistance is normal, and there are not excessive (custom) electrical loads on the bike, and the end-of-charge battery voltage is too low, then the regulator "charge done level" is faulty and the regulator needs replacement.

[b. After a normal start, 10-15 minutes of normal riding should allow the charging system to replenish the energy taken from the battery during the start. After a difficult start, with lots of cranking, recharge can take much longer. That implies a problem outside of the power generation subsystem. ]
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post #2 of 5 Old 02-26-2016, 07:00 PM
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Originally Posted by Trepidator View Post
The resistance across each of the 3 pairs should be no more 0.3 Ohms higher than what your meter reads with its leads pressed together hard. Those readings should be uniform for the same contact pressure between probes and pins. (Probe lead resistance and probe contact resistance tend to swamp the winding resistance being measured, so interpret readings accordingly.)
Just FYI, I've done this winding resistance check on dozens of motorcycle models with the same style charging system (but not the 2012-2016 DL650 yet), and the readings I get are normally in the range 0.7 to 1.1 Ohms. (So to those watching -- don't condemn your stator if you're working on a different model and you don't get 0.3 Ohms.)

I wonder -- does this mean the late-model Wee's stator uses bigger wire with fewer wraps than other DL stators? It might be interesting to see a photo of one and compare it to an early Vee stator.

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post #3 of 5 Old 02-27-2016, 12:13 AM Thread Starter
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Quote:
Originally Posted by bwringer View Post
Just FYI, I've done this winding resistance check on dozens of motorcycle models with the same style charging system (but not the 2012-2016 DL650 yet), and the readings I get are normally in the range 0.7 to 1.1 Ohms. (So to those watching -- don't condemn your stator if you're working on a different model and you don't get 0.3 Ohms.)
Many older DMMs have a substantial lead resistance which obscures measurement in the sub-Ohm realm, which is where V-Strom stator resistance is. Most two-wire, low-Ohm measurements also suffer from added contact resistance. I tried to specify a measurement where the lead and contact resistance would be largely taken out. I padded the pass criterion to allow for measurement uncertainty which arises from correcting for that stray resistance. (I, too, wanted to avoid false failure indication.)

I agree that it would be a mistake, and possibly very troublesome, to see a measurement with much added contact and lead resistance and conclude that the stator is damaged. Anybody who is unwilling to measure the lead and contact resistance and use it to calculate the result (as I outlined) should avoid using my winding resistance measurement procedure.

Quote:
Originally Posted by bwringer View Post
I wonder -- does this mean the late-model Wee's stator uses bigger wire with fewer wraps than other DL stators? It might be interesting to see a photo of one and compare it to an early Vee stator.
In order to deliver 30A to the B+ DC bus, stator resistance must be well under an Ohm to keep from rapidly self-destructing. I do not think the fact that stator windings are under 0.3 Ohms implies that they have been subject to any major changes.
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post #4 of 5 Old 02-27-2016, 09:59 PM Thread Starter
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Post stator winding resistance, 4-wire measurment

(A refinement of expected stator winding resistance follows. This is mainly interesting to technical folks, if anybody. There is a "bottom line" result at the end.)

Today, I undertook an initial accurate measurement of the Suzuki stator recently removed from my DL-650AL3.

As I was riding today for several hours, I was pondering how to accurately perform a 4 wire stator resistance measurement on the bike by some means other than hauling one of my DC bench supplies out of my lab, setting its current limit and measuring that, applying it to windings (one at a time), and measuring voltage with a DMM. The question I posed was, "Wouldn't it be nice to have a small current source for resistance measurement using the 4 wire method; what would that look like?" The answer followed in fairly short order once I had the right question: It would have a small battery and a little circuit acting like a low-value current source. Then, the light bulb lit: That's what a DMM does when it is in Ohms measurement mode. The 4 wire measurement can be done with 2 DMMs. (I knew there was a reason to keep my plain old Fluke 76.)

Using my portable 305 microAmp current source to inject current into the ends of the terminals on the stator windings, I measured a reasonably stable 60 uV on the crimp end of the terminals. This shows that the resistance is about 197 {a} milliOhms. This value is not corrupted by lead resistance or contact resistance. It is pure accident that this is close to the 0.2 Ohm value I got earlier using a 2-wire measurement crudely corrected for stray resistance.

{a. There was a detectable but negligible thermoelectric effect at work occurring at the contacts and other interfaces between dissimilar metals, so I consider the 3rd digit in that figure to be suspect for that reason beyond the 1 uV resolution of my Fluke 189 DMM. After handling the connector to insert 4 probe tips, I had to wait for temperature gradients to settle out. }

This result means that a bike capable of delivering 408 Watts to the B+ bus with a shunt regulator is dissipating over 140 Watts in its stator windings. My next task is to see how hot they get.

======= Bottom Line =======
The stator I measured has 0.20 Ohms of resistance at a temperature between 66 and 68 degrees Fahrenheit.
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post #5 of 5 Old 03-03-2016, 04:15 PM Thread Starter
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Post Stator or Rectifier fault very bad for the other.

In post "V-Strom Power Generation Checks", I wrote:
Quote:
Originally Posted by Trepidator View Post
...
A Precaution Re DC Generator:

There is a pitfall in replacing only the rectifier/regulator or only the magneto stator if either has been damaged by the other. The rectifier diodes are individually under stress approaching what could damage them, and a short in the wrong place on the stator can result in much higher than normal current going through the diodes furthest (electrically) from the short, possibly damaging them. It is also possible that failure of one or more rectifier diodes would cause excessive stator current, damaging it. For this reason, I recommend (as does the service manual) verifying the operation of both the rectifier/regulator and the magneto when either has been implicated or replaced.
Last night, I modified my PMG/rectifier/load simulation to model the effects of: (1) stator winding short to ground near Y join; (2) stator winding short to ground near a stator terminal; (3) a shorted diode in the bridge rectifier; and (4) an open diode in the rectifier. I did this to see how badly stressed other components become when any one of these faults occurs. (I also wanted to see how much power continues to flow to the battery/loads from the regulator.)

The results confirm the advice given above. They also show why multiple scorched places show up in failed (and removed) stators.

Either of the winding shorts shifts heating stress so that the rectifiers connected to ground suffer about 3 times the heating of the ones connected to B+. (For a series regulator, the same effect will occur for the SCRs used in place of diodes.) Total rectifier dissipation only increases about 10 percent but instead of dissipating about 10W each (in 6 places), the three connecting to ground dissipate about 45W, with the one connected most directly to the shorted winding dissipating 19+ Watts, almost double the usual heating stress. This could easily lead to that diode failing short.

Any single bridge diode short results in driving total stator dissipation from about 140W to about 260W, which would be bad enough for the marginal V-Strom stator if the excess was evenly distributed. But it is not; the hardest hit winding, (which is the one connected to the shorted diode), gets nearly 3 times the heating as compared to normal. This will damage the stator.

Any single bridge diode open increases the attached stator winding dissipation by about 50 percent. This is also bad for the marginal stator. It is more insidious because delivered power from the bridge is almost unaffected, make this failure unlikely to be noticed until the stator also fails because of it.

The shorted-to-ground stator failures can remain hidden for awhile because, for most of the possible short locations, the magneto/bridge combination continues to deliver enough power to barely run the headlights and engine. This means that the extra stress such a short imposes upon the bridge, (mostly in one diode), can have a long time to act, degrading the diode.

In all cases, the excess dissipation arises from two phenomena: redistribution of stress, concentrating it more on a single element; and creation of large DC currents which flow uselessly, (in the stator), because the positive/negative symmetry of the stator/bridge combo is broken.

The bottom line here is this: Changing out either the stator or rectifier/bridge without carefully checking the other component is risking an expensive (in time, money, or both) additional failure. In the worst, case, a naive might change one after the other, then wonder why the power generation system continues to misbehave. (After all, brand-new components must be good!)
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Last edited by Trepidator; 03-03-2016 at 06:55 PM. Reason: spelling, punctuation, and removed gratuitous understatement of hazard
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