Protecting the Alternator Regulator from Incorrect Shutdown

[goboatingnow]

So it was pure coincidence that the alternator stopped working the moment this was done?

as other posts have said, the "ignition" key should never have the alternator supply fed through it and in practice Ive never seen it done ( Maine Sail). Therefore theres no way to damage anything if you turn it off. electricity isnt voodoo.

Also in practice its a very easy mistake to make as many people think its like a car. Hence Ive never seen the igniton key wired to cause any trouble if it was turned off before the engine stops.( and in fact on many motor boats the key is wired to fucntion exactly like in a car, with a loss of electricity to activate the stop)

Dave

[senormechanico]

After looking through the Mouser Electronics catalog, I found no Zener diodes as big as I had recommended.
In actual practice, the current and voltage spike which needs to be absorbed by the zener is of such a short duration that one doesn't need a powerfully rated diode.
The one suggested by Gord would suffice.

[goboatingnow]

Originally Posted by senormechanico

After looking through the Mouser Electronics catalog, I found no Zener diodes as big as I had recommended.
In actual practice, the current and voltage spike which needs to be absorbed by the zener is of such a short duration that one doesn't need a powerfully rated diode.
The one suggested by Gord would suffice.

I fail to see unless you want to protect the alternator against the battery switch being inadvertently disconnected, why you would want to use transzorbs or other protective devices. Most of these devices can tend to have a one time use and it may not be obvious that they are dead. also many modern alternator regulators actually contain "crowbar" circuits that protect the regulator and diodes.


But the OPs problem wasnt this.
Dave

[svHyLyte]

Originally Posted by goboatingnow

This is a bit of a marine "old wives tale", There should be no electrical reason why shutting off the "ignition", before stoping the engine, has any electrical effect. other then de-powering the panel and de-energising the alternator "excite". sometime rule was needed as the power to the stop solonoid was passed through the ignition switch, which is bad practice.

Dave

David--Your observation may be entirely correct. Never the less, over the years I have seen several instances on several yachts where shutting off the "ignition" (undoubtedly a misnomer) before the engine stop cause problems with wiring for whatever reason--and in one case disallowed the engine stop solenoid to work at all. Given that, shutting the engine down before closing the power circuit seems an easy enough procedure, no?

[goboatingnow]

before the engine stop cause problems with wiring for whatever reason--and in one case disallowed the engine stop solenoid to work at all.

I mentioned that the only issue that can be a problem is that some panels disable the supply to the stop solenoid, so the panel/ignition has to be left on to stop the engine, its a bad setup.

Other then that there simply is no scenario where shutting down the panel affects anything. ( other then de-exciting the alternator in some cases). of course there are times when panels have become a wiring mess.

Dave

[GordMay]

Originally Posted by goboatingnow

... also many modern alternator regulators actually contain "crowbar" circuits that protect the regulator and diodes...

I wasn't aware of this. Please name one.

[motion30]

So the field wire from the alt needs to be connected to 12 volts If this is connected tru the ign sw will the alt be harmed when shutting off the sw? The field wire from my alt connects to 12v tru a oil pressure switch When oil pressure rises the alt charges when the oil pressure drops no charging Is this normal?

[AnchorageGuy]

Originally Posted by motion30

So the field wire from the alt needs to be connected to 12 volts If this is connected tru the ign sw will the alt be harmed when shutting off the sw? The field wire from my alt connects to 12v tru a oil pressure switch When oil pressure rises the alt charges when the oil pressure drops no charging Is this normal?

Our Ford Lehman 120 in our trawler is set up the same way. Most of these Marine Traders are set up that way too. Chuck

[senormechanico]

Originally Posted by motion30

So the field wire from the alt needs to be connected to 12 volts If this is connected tru the ign sw will the alt be harmed when shutting off the sw? The field wire from my alt connects to 12v tru a oil pressure switch When oil pressure rises the alt charges when the oil pressure drops no charging Is this normal?

IMHO, that's the best way.
Shutting off the switch causes the alternator to quit charging, thus protecting the diodes in the alternator.
By routing the 12 volts through an oil pressure switch, it allows for a delay in charge start.
This preventing the starter motor from having to deal with a larger alternator load while cranking the engine.

[Maine Sail]

Originally Posted by GordMay

I wasn't aware of this. Please name one.

Ditto. I know none of the Balmars are protected and have not come across any Leece-Neville alts that are either and I install a lot of both.. Perhaps on the automotive side of the world but I see no point in this extra cost added feature...

I would love to know which alts are internally protected from load disconnecting and is this a "one time" feature like many of the Zap Stop devices are?

[goboatingnow]

Originally Posted by GordMay

I wasn't aware of this. Please name one.

European vehicles must meet ISO 7637 pulse 5 test, which is a load dump test, simulating disconnecting the battery lead while the alternator is powered up. The Test pulse must be successfully clamped. This was done with Transzorbs, now increasing done with FET clamps. These are now being built directly into European alternator regulators.


Dave

[Astrid]

Also being found in a number of alternators for use in aircraft. If the circuit detects an overage, the crowbar shorts the extra load to ground and trips a circuit breaker to protect the alternator.

http://www.planepower.com/images/Bro...LTERNATORS.pdf

http://www.lightaircraftassociation....04OverVolt.pdf

[tropicalescape]

Did someone say that turning the battery switch off while the engine is running will cause problems?mine is a yanmar gm2-20f if it makes a difference.Thanks DVC

[Maine Sail]

Originally Posted by goboatingnow

European vehicles must meet ISO 7637 pulse 5 test, which is a load dump test, simulating disconnecting the battery lead while the alternator is powered up. The Test pulse must be successfully clamped. This was done with Transzorbs, now increasing done with FET clamps. These are now being built directly into European alternator regulators.


Dave

Any alts for marine use sold in the US with this? Seems like a good fit...

[SV Demeter]

My 8 year old frequently forgets to push the stop prior to turning off the key. No problems yet other than panel goes dead and electric lift pump stops which I guess could cause a problem after a bit. I'm curious how the OPs kit could have been wired with the load thru the key switch. I would not think the key switch could handle the amps for that long.