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-   -   The KTM Duke 390 Ownership Experience Thread (https://www.team-bhp.com/forum/motorbikes/138082-ktm-duke-390-ownership-experience-thread-398.html)

It indeed was the rectifier which has gone kaput, got it replaced under warranty, no charges as I had the 3rd service also done along with this issue.

Looks like my battery is on its last leg after a three and half year stint. Yesterday had been to Malleshwaram for a breakfast meet with Bhpians and the error popped up just as I was leaving the place. Cranked a couple of times but just as the starter starts the error pops up on the MID. Since it was on an incline, managed to push the bike down and start. Reached home and tried starting and found no issues any number of times. But today morning it refused to start on the first crank and then started fine on the second. Have asked the SVC to check their inventory for a spare one. Will replace it rather than getting stranded.

How does it throw away half the current as heat? A circuit diagram would help.

Regards
Sutripta

I may have grabbed the wrong quote but the question I am answering asks why I mentioned that rectifiers get hot and how do they work.
Hopefully this will help

I probably should have said, "some rectifiers throw away half of the current..."

There are basically two types of rectifiers.

The half-wave rectifier receives both + and - charges from the alternator.
It passes either one or the other along to the electrical circuit and the other charge is lost as heat.

This link will explain it

http://www.electronics-tutorials.ws/diode/diode_5.html

The full wave rectifier circuit is more complex but to put it simply, it passes both the + and the - on to the electrical circuit sending the + pulses to the DC + side and the - pulses to the DC - side.

It looses much less power and provides a smoother, power to the DC circuit.

This link will explain it

http://www.electronics-tutorials.ws/diode/diode_6.html

Computers, being the fussy things that they are like to see a uniform supply of power so the fuel injected motorcycles are much more likely to use the full wave rectifier.

That doesn't remove the rectifier from being a likely suspect when the charging system in a motorcycle stops working.

The RR is a rather small thing and it is handling fairly large amounts of power so occasional failures are to be expected.

I hope this helps the people who are interested. :)

Must say that I still don't get the 'throw away half the current as heat?'
What current/ power? And where is it dissipated? Diodes? Windings? Somewhere else?

Regards
Sutripta

A bike's generator (magneto) produces electricity with a fixed magnetic field from the magnets in the rotor/flywheel. Since the field strength is constant, the current produced is is also constant but the voltage varies proportionately with RPM. So it is likely that the magneto is producing greatly excessive power (V * A). The voltage is controlled by dropping the voltage across a variable "resistor" like a transistor or triac. Since there is a significant excess of current, the power to be dissipated as hear is also very high (relatively). This is the "throw away a lot" part.

A car's alternator differs by having an electromagnet to produce the magnetic field. The electromagnet is the rotor. A part of the generated current by the stator is fed back to the rotor windings. By controlling the stator current, the magnetic field and hence the stator current is controlled. This means that only the amount of current required is produced. The voltage is still proportional to RPM so that still needs to be regulated. The voltage regulation circuit is similar to that of a magneto but as the excess power is minimal, the job of the voltage regulator in an alternator is much easier than that of a bike and that's why it's also a lot more reliable.

Quoting my own thread. Replaced the battery at Mekhri circle SVC today. The voltage on cranking was dropping to 7.6V sometimes while it was a healthy 12.6V during rest and going upto 14.3V during acceleration. A battery tester check proved it was indeed dropping on cranking. I had to push start the bike on an incline on a couple of occasions since Monday which made me more averse to failure sometime soon.

Damage to wallet was 2106INR. The stock battery lasted for 3.5 years and 32050kms on the odo.

My battery was showing red on the load meter since a year and I had been ignoring it. Absolutely no issue except a few understandable "Low Battery" messages on mad winter morning starts. Finally decided to replace it, as I couldn't kid around with a very crucial component of the bike anymore. It had done it's time.

Replaced mine at 25k after around 2.5 years, yesterday.

Exide Explore XLTZ9 with 4 years warranty for Rs.1650/- after exchange (Rs.200) of the old one.

My initial problem was with the term half (which I should have highlighted)
Which was taken to a whole other level of confusion when it was linked to half wave rectification
Essentially because when the diodes are reverse biased, there is no current flow (lets not get pedantic about leakage current). No current => no power generated or withdrawn => no power to dissipate.

Always found that alternators cause a lot of confusion, more so in bikes. If someone could write a tutorial on it, it would be great.
At the very least
a diagram showing the position of the coils, both physically and electrically, and their physical relationship to the magnets,
a circuit diagram of any common RR, with clear explanations of its two functional parts:- rectification, and regulation, and how the circuit achieves this.

Can a Triac (or SCR) be used as a 'variable 'resistor''?

On a slightly different note, if we are to work out some quantitative values, would it be better to model the bike alternator as a voltage source, or a current source?

Regards
Sutripta

Hello Dukes :)

I am finally a a proud owner of a pre-worshipped 2013 Duke 390. Having ridden the bike for a day or 2, I am experiencing the following issues :
1. Bike heating up - especially in traffic
2. Some swishing sound from the bottom of the bike (sounds like chain rubbing against plastic)

I found link which mentions about 15 changes done to the 2015 Duke 390 - 2 of which seem like a solution to my problems.

2015 KTM Duke 390 – List of 20 changes explained

Are these 2 upgrades possible on the 2013 D390? Has anyone done this upgrade on their bike?

I am not an expert on this - wasn't this the solution that was being implemented by some innovative/knowledgeable mechanics in the "golden days" of Yezdi ?

As old timers here will recall - it was practically next to impossible to find a Yezdi with a fully functional battery - culprit the rectifier (not that anyone wanted/bothered about the battery, which was practically only for the horn, which anyway was not needed at all because of the basic sound of the Yezdi :)).

With this system which the mechanics would call "diode" the problem used to get solved to a large extend (to be read as the battery used get charged enough to enable honking, once the bike had run a few KMs from a cold start)

Best Regards & Ride Safe

Ram

My days off applying Thevenin's theorem or Norton's theorem are long past so I no longer know what type of source an alternator should be. But I think both types are interchangeable. An electrical or electronics engineer could give you the right answer.

What I know and have retained are just the fundamentals of electrical and electronics. These have helped me a lot in my job of designing industrial machinery. Sadly, many freshers I interview just don't know any basics in any field and finding competent people at lower levels is a big challenge.

Congrats on the Duke v12. I think the fan mod should be possible and worth a check at the service center. Not sure of the 2nd point as you have put the same point twice and also the link you have provided does not seem to work at office. Will check and respond once I can access the link.

Thanks Abhinav, will check with the ASC when I go there for the service. This was the other update on the 2015 model - which I think could be the solution to the swishing sound.

Triac as dissipaing element?:- Short answer - no. The triac works as a switch. It is the controlling element, not the dissipating element. Not to be confused with the fact that the triac will heat up and almost certainly require a heatsink.

When the regulator is working, and current output is within design limits, terminal behaviour is close to that of (an ideal) voltage source. So I should have added 'without regulator present'. Reason for asking was
where emphasis seems to be on stator current.
BTW, I think 'stator' (highlighted) is a typo, should be rotor.

Regards
Sutripta