Alternators in 58YF

[first230sl]

I have a charging problem on my port side that I am very close to diagnosing and fixing. Almost there. The Calder book came in very handy for an understanding of charging systems.

When I was crawling around the boat making up a wiring diagram for the charging system (Hatteras could not supply me with one) it became apparent that there is no battery field excitation line - unless I missed something. The positive terminal of the regulator is switched by a pressure switch near the secondary fuel filter, but no excitation circuit. Are these self-exciting alternators?

I have attached a photo of the alternator and regulator. I am not 100% sure, but I believe the alternator is a Delco Remy 30 DN Type 250 Alternator. Could find precious littleinfo on the web.

Thanks! Murray

 

[Nonchalant1]

The alternator has a plate on it with the numbers. If it's an "alternator" it seems to me that it wouldn't need a regulator. If it's a generator, it would. My Delco alternators have no regulator and have only one large positive wire and one negative ground connected to them. The regulation is internal. A number of boats with generator/regulators have replaced them with alternators for reasons of simplicity and reliability.

It's very easy to take them off if they're the belt driven kind. The local Delco shop up here runs a free test by putting them on a bench stand operation test to see if they're running up to faactory specs. I guess they figure that enough of them will need work to make the free testing pay off (but mine came out OK). If yours are direct drive, it's a completely different story.

Doug Shuman

 

[Trojan]

Most external regulated alternators do not self excite.There must be a wire from the regulator. Single wire alternators can be eather way. Most single wire alternators are self excite. Chrysler alternators had external regulator and do not self excite. GM alternators can be converted over. Its just a wire and a diode.Bill

 

[first230sl]

Thanks - on my boat they are indeed alternators, and are extrnally regulated. My understanding of the alternaot/generator semantics is that generators produce voltage & current in the rotating windings which is rectified physically by the commutator - the field is stationary and surrounds the rotor. An alternator produces current/voltage in the stationary stator and the field windings rotate - allowing for smooth slip rings and lighter rotor. Here the rectification is done electronically using diodes formed into a bridge rectifier.

On reflection I believe it is the case that the initial excitation of the field is done by the regulator using the same field wire as is used to control alternator output. The Calder book talks about a separate excitation circuit that electrifies the field momentarily during startup, gets current flowing, and then turns off to let the regulator take over. He spoke of it being necessary because the alternator needs to supply the field excitation voltage, but can't do so unless there is current in the field to begin with. I was confused when I read it because it seemed unnecessary as long as the regulator had power from the battery (which it does). And since there appears to be no such line, I am at a bit of a loss as to what he is describing and why it would be necessary.

Oh well - I am convinced I understand it all more than enough to fix the problem (which I now believe to be a faulty relay in the field circuit - will know for sure when I take it out to test). I'll just have to let the rest be a mystery - though I know I'll be bothered by it until I figure out what he was trying to say. Maybe Calder will answer e-mails?

Take care and thanks for the help.

Murray

If it's an "alternator" it seems to me that it wouldn't need a regulator. If it's a generator, it would. My Delco alternators have no regulator and have only one large positive wire and one negative ground connected to them. The regulation is internal. A number of boats with generator/regulators have replaced them with alternators for reasons of simplicity and reliability.

It's very easy to take them off if they're the belt driven kind. The local Delco shop up here runs a free test by putting them on a bench stand operation test to see if they're running up to faactory specs. I guess they figure that enough of them will need work to make the free testing pay off (but mine came out OK). If yours are direct drive, it's a completely different story.

Doug Shuman

 

[Trojan]

Some alternators have enough self-contained magnetic power to self excite.Your correct in that there is a diode jumper that excites the field .The bridge rectifier will not let voltage back into the field (like a water check valve) so the field is not charged. In comes the jumper diode, this is low voltage. Just enough to start the fields producing current.Then the alternator takes over. After the takeover the ziener diode does nothing in the unit, it is preset and will not very above its preset voltage. Once the alternator is producing voltage it nolonger needs the battery to operate. We used to check them by disconnecting the battery. If the car still ran the alternator was ok. Not a good idea today. The alternator of today needs the battery for a load to regulate .Bill

 

[Trojan]

With the key on you should have some field voltage. If not change the regulator. Bill