[ROVERNET - UK] Re: Electrical Question

[Slatskars]

You are correct David. It should be pulsating DC with minor ripples at that 
RPM rather than AC, with a bridge rectifier.

Slats
----- Original Message ----- 
From: "David Read" <defender110 at ozemail.com.au>
To: <rovernet at lyris.ccdata.com>
Sent: Sunday, May 13, 2007 8:22 PM
Subject: Re: [ROVERNET - UK] Re: Electrical Question


> Measured across the battery ...
> My Fluke reads 14.2 on DC volts and 0.0016v on the AC volts, but it is 
> hard to tell what the effect of having the battery in circuit has on the 
> waveform.
>
> WARNING:- *DO NOT* disconnect battery from alt whilst engine is running!!
>
> At 4000 engine revs the approx output ripple frequency would be 800hz
> (assuming 12 pole field and 2:1 engine/alt pulley ratio)
>
> From the theory of 3 phase full wave rectifiers ....
> Vdc out= Vac(rms)in x 1.35
> Ripple freq out = 6 x generated frequency
> Ripple out 4.6% of output
>
> I don't call 4.6% substantial.
>
> Cheers
> Dave
> South Oz
>
> Paul Smith wrote:
>> Disagree there...
>> you will get substantial AC on a multimeter when the diodes are ok too.
>> The mm just puts a capacitor in line, so any variation in DC will be seen 
>> as AC (it is AC with DC shift).
>> I think he has a generator anyway.  I have sent him the next stuff to 
>> check out.
>>
>> PVS
>>
>>
>> -----Original Message-----
>> From: rovernet-bounces at lyris.ccdata.com
>> [mailto:rovernet-bounces at lyris.ccdata.com]On Behalf Of David Read
>> Sent: Monday, 14 May 2007 10:53 am
>> To: rovernet at lyris.ccdata.com
>> Subject: Re: [ROVERNET - UK] Re: Electrical Question
>>
>>
>> H Walter
>>
>> Walter Reynolds wrote:
>>> Thanks for the quick responses.
>>> In answer to Paul:  IGN light goes out when ignition turned off.
>>
>> That's ok
>>
>>> In answer to David:  Battery at rest shows 12.5 volts on my volt meter. 
>>> This drops to 12.0 v at engine start and drops further to 11.75 v after 
>>> 3 minutes running.  After 5 minutes is's still at 11.75v.
>>
>> EEEK!!
>>
>> Doesn't sound good at all. Suspect regulator or a blown diode or two.
>> If the diode/s are US, the average (DC) voltage of the output waveform 
>> may well be below 12v.
>> Try putting your multimeter on *AC* volts with the engine running. If it 
>> reads anything substantial, then the diodes are definately suspect as raw 
>> AC is getting to the system.
>> Your battery will be suffering in the long term as well.
>>
>> Cheers
>> Dave
>> South Oz
>
> _______________________________________________
> rovernet mailing list
> rovernet at lyris.ccdata.com
> To unsubscribe, go to this web page, look near the bottom and follow 
> instructions:
> http://mailman.nipltd.com/mailman/listinfo/rovernet
> Back-up list and photos at:
> http://autos.groups.yahoo.com/group/Rover_net/