>From that schematic, it is indeed a simple waste/dump regulator,with the two
>failing
diodes being there to prevent battery from reverse feeding during the dumps.
It is pretty silly that they undersized them for rated alternator generating
current capacity. "Certified". Wow.
Cheers,
Pete
> On Jan 21, 2014, at 4:12 PM, Bill Henderson <europa10@bellsouth.net> wrote:
>
> As info.....
>
> I opened up one of the Rotax regulators a friend gave me after a failure. The
two diodes were bad and were open so paralleling them with external diodes does
seem to be a viable option. Relatively cheap for the cost of the diodes and
a heat sink. No modification to the existing regulator required. Attached
is the fix I obtained from another website. Just need to join the diodes to the
B and two G terminals.
>
> Just my two cents worth.....
>
> Bill
> A010 Classic Monowheel
> Still building.
>
>
>
>
>> On 1/21/2014 3:02 PM, Jan de Jong wrote:
>>
>>
>> ad A:
>> Don't agree. The only stress would be somewhat higher reverse voltage. The
>> Ducati
R/R is not a shunt regulator.
>>
>> ad B:
>> Agree, but the thyristors are more stressed than the diodes. They drop a
>> little
more voltage and dissipate more heat.
>> On the other hand, the custom fitting of the diode pills could be more
>> uncertain
than the standard fitting of the thyristors (TO220 I believe).
>>
>> Parallelling the diodes with external ones is possible. They would require a
heat sink. Are the failure statistics clear about the diodes?
>> I think it would be better to get an R/R without issues.
>>
>> Regards,
>> Jan
>>
>>
>>> On 1/21/2014 6:30 PM, Greg Fuchs wrote:
>>>
>>>
>>>
>>> Well, since the generator is not a two-legged 'phi' connection (i.e. the
>>> midpoint of the generator coil connected to the ground of the system or
>>> vehicle, then 'dumping to ground' may not be the term to use after all. Yes,
>>> I think that is correct.
>>>
>>> Here are the two main failure modes of the Ducatti regulator as I see it..
>>>
>>> A) If the aircraft has a very low load usage (i.e. no lights, no
>>> instruments, etc.), the scr's are stressed and 'may' fail eventually. If
>>> this happens, the Ducatti is unrecoverable.
>>>
>>> B) If the aircraft has a very high load usage (using up most of its 15-18
>>> amps), the output diodes are stressed and probably will fail eventually,
>>> which is backed up by historical data gathering (they fail a lot at high
>>> loads per many forum users). The Ducatti would then be recoverable by
>>> placing 25 Amp or higher diodes on the external terminals as referenced
>>> earlier.
>>>
>>> Scenario (A) is unlikely, since everyone likes power-hungry instruments and
>>> the like, where scenario (B) is the most likely for the same reason.
>>>
>>> Thus, if someone wants to 'beef up' their ducatti, then they have the option
>>> to place the external diodes. I guess it doesn't matter what kind, as long
>>> as they can withstand the current from the generator. They will either help
>>> the internal diodes survive almost forever, or take over for them when they
>>> fail (It depends on the turn-on points between the internal and external
>>> diodes).
>>>
>>> Jan, do you agree with this?
>>>
>>> Best Regards,
>>> Greg
>>>
>>> -----Original Message-----
>>> From: owner-europa-list-server@matronics.com
>>> [mailto:owner-europa-list-server@matronics.com] On Behalf Of Jan de Jong
>>> Sent: Tuesday, January 21, 2014 4:59 AM
>>> To: europa-list@matronics.com
>>> Subject: Re: Europa-List: Re: Ducati rectifier/regulators
>>>
>>> Equally respectfully - "dumping to ground" is not dumping, but connection to
>>> the negative DC output terminal.
>>> I attach a little OpenOffice drawing that hopefully clarifies (I hope that
>>> works).
>>>
>>> Regards,
>>> Jan
>>>
>>>> On 1/20/2014 11:21 PM, Greg Fuchs wrote:
>>>> --> <gregoryf.flyboy@comcast.net>
>>>>
>>>> Respectfully, I believe that the circuit configuration that you are
>>>> thinking of is incorrect, Jan de Jong.
>>>>
>>>> The SCR's do EXACTLY 'dump' the AC output DIRECTLY to ground.
>>>> When one end of the thyristor connects to the alternating current
>>>> output of the coil, and the other end to ground...then that is all
>>>> they can do but short the AC output to ground. It is not acting as a
>>>> PWM-like device at all, simply a grounding device. Call it a
>>> direct-connect.
>>>> You mention heat. The direct-connect method is the best way to deal
>>>> with the heat. The forward voltage drop of the 'dumping' device is
>>>> low, and the current does not need to go through the diodes at all,
>>>> which are bypassed...hence your lowest heat output.
>>>>
>>>> Since the 'dumping device' connects the alternator output directly to
>>>> ground, without going through the diode, what is the power dissipated?
>>>> While in the dumping mode, lets say the current to dump was 10
>>>> amps(I'll use your generously supplied information, so I don't have to
>>>> look up specs) it would be 1.1V * 10 amps. That's it. 11 watts. That
>>>> is much better than the 18 Watts in your configuration.
>>>>
>>>>> (
>>>>> a failure mode for the Ducati device is reportedly the loss of
>>>>> continuity
>>>> of a diode pill attachment through thermal >cycling; fitting external
>>>> parallel diodes has been proposed as a solution; replacing the whole
>>>> device seems more
>>>>> sensible
>>>>> )
>>>> Well, maybe so! However, if the failure mode is a loss in continuity,
>>>> that would mean the diodes are opening. That would also mean that
>>>> connecting the external diodes to the regulator would bring it back to
>>> life!
>>>> Regards,
>>>> Greg
>>>>
>>>>
>>>>
>>>> -----Original Message-----
>>>> From: owner-europa-list-server@matronics.com
>>>> [mailto:owner-europa-list-server@matronics.com] On Behalf Of Jan de
>>>> Jong
>>>> Sent: Monday, January 20, 2014 7:40 AM
>>>> To: europa-list@matronics.com
>>>> Subject: Re: Europa-List: Re: Ducati rectifier/regulators
>>>>
>>>>
>>>> Re two-phase bridge rectifier/regulator.
>>>> The 2 thyristors in the rectifier bridge do not short the AC input or
>>> "dump"
>>>> anything.
>>>> On the contrary, they disconnect the DC output from the AC input when
>>>> the output voltage threatens to exceed the set voltage.
>>>> All output current passes through one branch of one diode and one
>>>> thyristor in series half the time and through the other identical
>>>> branch also half the time.
>>>> Heat development is proportional to the output current and the voltage
>>>> drop across a branch.
>>>> Voltage drops increase somewhat with current, so heat development
>>>> increases more than linearly with output current.
>>>> In the Ducati device the diode is reportedly a MR2510 pill (typically
>>>> 0.75V at 10A, 0.8V at 20A), the thyristor can be a 2N6504 (typically
>>>> 1.1V at 10A, 1.3V at 20A).
>>>> So at 10A the two branches of the bridge are each expected to generate
>>>> 0.5 x (7.5 + 11) = 9.25W (total 18.5W) of heat.
>>>> And at 20A the two branches of the bridge are each expected to
>>>> generate
>>>> 0.5 x (16 + 26) = 21W (total 42W) of heat.
>>>>
>>>> (
>>>> a failure mode for the Ducati device is reportedly the loss of
>>>> continuity of a diode pill attachment through thermal cycling; fitting
>>>> external parallel diodes has been proposed as a solution; replacing
>>>> the whole device seems more sensible
>>>> )
>>>>
>>>> Cheers,
>>>> Jan de Jong
>
> <Rotax Regulator Fix.doc>
|