Re: [PSUBS-MAILIST] trolling motors?

[Subscuba@aol.com]

Herve,

Most of the permanent magnet motors require a controller (current limit) to 
prevent peak armature currents from demagnetizing the stator magnets. I can 
expand on this if you like but if you take a look in the PSUBS archives 
there's more information there. If they don't answer your questions, I can 
elaborate. Once you design and build a current limit, it's easy to make it a 
speed control. I wonder, if you are not using any controller on the MK motor 
you said failed, perhaps the stator was demagnetized? I think you stated a 
speed control was not really needed on these subs and I agree, but for this 
type of motor you do need a current limit.

From what you have stated on your previous messages and messages from others, 
apparently the MG has some of the electronics in the motor housing. Perhaps 
the Dura amp modules contain the power switches which require heat sinking. I 
believe that's why 5 wires are required, maybe. The four wires used in the MK 
are simply the two armature leads. Two red leads are used for the positive 
lead and two black for the negative armature leads. A review of your last 
message seems to imply you don't use any kind of current limit or speed 
control. Do you just switch 24 or 36 volts to the motor? 

In any case, I'm not too familiar with the Motor Guide motors in that much 
detail. I just don't like putting any electronics in the motor housing and 
that's just a personal preference.

I wish MK made a three blade prop, but I have not been able to identify one.

From your address it looks like you operate subs in the Caribbean. Can you 
elaborate on that? I do a lot of diving in that area.

Have fun,

Ken Martindale

In a message dated 11/26/00 2:58:50 PM Eastern Standard Time, 
caribsub@coqui.net writes:



> Ken,
> I am not quite sure to understand what you mean by "controller", because 
> there is not much electronic inside the lower unit of a MG. please 
> elaborate.
> MK lower unit has only red and black wires going into the lower unit, an 
> electronic board is in the top housing for speed controls
> MG lower unit has 5 leads going inside, there is an electronic module for 
> speed control in the top housing, like in MK, and a brush card inside the 
> lower unit on which are connected the wires and a Dura amp module.