Shaft generator doesn’t load


Roland Mueller
 

Hi,

Our shaft generator was working fine, but after a total breakdown of our 24v supply (24v alternator defective and Onan generator not starting), it doesn’t load anymore.

Before the 24v breakdown, both control lamps (green and red) were off, when the shaft generator wasn’t in use. After the 24v breakdown and after recharging the batteries with shore power, the red control lamp is permanently on, even the control switch is off:
image0.jpeg

When trying to start the shaft generator (switch on, with enough speed under sails, and the prop turning backwards), normally the green control lamp should be on, but in our case the red control lamp remains continuously on, even sailing with 7 knots:
image1.jpeg

All cables at the shaft generator are well connected. It seems like the 24v breakdown changed some settings to enable the shaft generator to start loading.

Has anyone experienced this issue and knows how to solve it?

Regards,
Roland 
SM 150 Aventura 
Currently at Isola d’Elba


Roland Mueller
 

Hi,

Our shaft generator was working fine, but after a total breakdown of our 24v supply (24v alternator defective and Onan generator not starting), it doesn’t load anymore.

Before the 24v breakdown, both control lamps (green and red) were off, when the shaft generator wasn’t in use. After the 24v breakdown and after recharging the batteries with shore power, the red control lamp is permanently on, even the control switch is off:
image0.jpeg

When trying to start the shaft generator (switch on, with enough speed under sails, and the prop turning backwards), normally the green control lamp should be on, but in our case the red control lamp remains continuously on, even sailing with 7 knots:
image1.jpeg

All cables at the shaft generator are well connected. It seems like the 24v breakdown changed some settings to enable the shaft generator to start loading.

Has anyone experienced this issue and knows how to solve it?

Regards,
Roland 
SM 150 Aventura 
Currently at Isola d’Elba


Bill Kinney
 

Roland,

What is the current voltage of the batteries?  If it is VERY, VERY low then there might not be enough voltage to generate the required field current.  I think this is unlikely, but possible.

Other than that, I can think of nothing that could be related between the a deep discharge of the 24V batter bank and the failure of the shaft alternator.  The first place I would check would be for voltage on the field wire to the alternator (the small wire).  If that is not +24V to negative, then that's the issue.  Find out where the break in the circuit is.

If there IS field current, then... it's time to dive into diagnoses of the alternator itself.

What happened to the main engine 24V alternator?  Why did that fail?

Bill Kinney
SM160, Harmonie
Le Marin, Martinique.


Roland Mueller
 

Bill,

The 24V alternator failed because the wire to enable charging was loose. After fixing this wire properly, the 24V alternator worked fine. And helped us to complete our journey from Leros/Greece to Genua/Italy.

The voltage of the 24V batteries is 25.8V, hence fully charged. There should be sufficient voltage to generate field current.
The voltage on the field wire to the alternator (the small wire) is measured 27.6V (currently at shore power).

What could be defective at the shaft alternator, that worked perfectly fine before our 24v supply breakdown? I can't believe it's a mechanical issue. We've check all wirer connected to the shaft alternator, just to make sure we are not fooled again by a loose wire.

Regards,
Roland




From: main@AmelYachtOwners.groups.io <main@AmelYachtOwners.groups.io> on behalf of Bill Kinney <cruisingconsulting@...>
Sent: Sunday, June 19, 2022 4:04 PM
To: main@AmelYachtOwners.groups.io <main@AmelYachtOwners.groups.io>
Subject: Re: [AmelYachtOwners] Shaft generator doesn’t load
 
Roland,

What is the current voltage of the batteries?  If it is VERY, VERY low then there might not be enough voltage to generate the required field current.  I think this is unlikely, but possible.

Other than that, I can think of nothing that could be related between the a deep discharge of the 24V batter bank and the failure of the shaft alternator.  The first place I would check would be for voltage on the field wire to the alternator (the small wire).  If that is not +24V to negative, then that's the issue.  Find out where the break in the circuit is.

If there IS field current, then... it's time to dive into diagnoses of the alternator itself.

What happened to the main engine 24V alternator?  Why did that fail?

Bill Kinney
SM160, Harmonie
Le Marin, Martinique.