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Re: [PSUBS-MAILIST] Oil Compensated Thursters
Thanks for the input Andy !
----- Original Message -----
From: "Andy Jensen" <drewacard@charter.net>
To: <personal_submersibles@psubs.org>
Cc: "Brian Cox" <ojaivalleybeefarm@dslextreme.com>
Sent: Tuesday, November 21, 2006 05:51
Subject: Re: [PSUBS-MAILIST] Oil Compensated Thursters
> I hate to but in, because both of you have good points.
> it will always be a trade off.
> facts
> 1 brush less DC motors are usually 3 or 4 phase AC running lower voltage some times with magnets
> 2 3 phase ac motors don’t usually have starter circuits.
> 3 ac motors are speed controlled by phase if you are running an DC to AC converter speed controller can be built in.
> 4 AC and Brush less dc motors have near flat power curves
> 5 DC to AC power controllers are around 90% efficant
>
> Andy J.
>
> ---- Brian Cox <ojaivalleybeefarm@dslextreme.com> wrote:
> Doug,
> I'm not exactly the brightest bulb in the tool shed ( however
> that goes) myself on electric motors. I just got done talking to the
> motor people here in Ventura where they rebuild motors for the oil
> industry. They use some DC motors and some AC as well. I think you
> will be able to be equally electrocuted whether you use AC or DC. In my
> situation my batteries and motor are going to be outside my pressure
> hull and I will be controlling it using low voltage. I don't know how
> brushless DC motors work unless maybe they are permanent magnet motors?
> If I'm not mistaken I believe the starter coils and centrifugal switch
> is an antiquated method but I could be wrong, don't they use solid state
> components?. These motor guys were telling me that the carbon from the
> brushes is THE major reason they rebuild motors. They were saying that
> just a tiny line of carbon will carry an electric charge to ground very
> easily, so in oil that could contaminate the windings and make a short
> very easily. So thats how I got to the AC motor scheme. I think there
> are a number of ways to contol the speed. The starting torque I
> wouldn't think would be a problem, unless you had a very large
> propeller. As my system stands at the moment I'm planning on having
> six 183 amp hour 12 volt batteries, so my next decision is how long of a
> time would I want at full power to determine the horsepower of the
> motor. I'm going back to the oil field electric guys to try and get
> straight on this and see what they would recomend.
>
> Brian
> ----- Original Message -----
> From: DJACKSON99@aol.com
> To: personal_submersibles@psubs.org
> Sent: Monday, November 20, 2006 21:32
> Subject: Re: [PSUBS-MAILIST] Oil Compensated Thursters
>
>
> Brian
>
> You mentioned that before, and I ignored it out of ignorance, so
> explain it to me. I think we use to use these in the warehouse on some
> of the feed mixing equipment. AC induction motors don't have brushes to
> contaminate the oil and with no brushes the voltage to cross the gap is
> a moot point right? And they done have electronic controllers because
> they use the AC cycle to flip the juice on and off right? But don't
> they do often have starter coils and centrifugal switch that kicks in
> the main coils once they are up to speed? And they have lousy starting
> tork too right?
>
> The down side has got to be having high voltage AC in a boat
> surrounded by salt water. ...you know, I have been shot, cut, burned,
> thrown from a motorcycle and I can tolerate lots of painful stuff, but
> Jesus, getting electrocuted is the thing I hate the most. Last time it
> happen I twitched the rest of the day. So what is the up side, beside
> no brushes? How do you control the speed? And why not use Brushless DC
> motors? They are my current choice, because they now come sensorless so
> there is nothing to crush, and the speed controllers are small enough to
> put in a small 1ATM box, and I can control the speed with a PWM signal.
> [These are the bigger hobby RC motors that I am looking at; 250 watt.
>
> Zzzzzapped --Doug J
>
>
> In a message dated 11/20/2006 7:40:49 PM Central Standard Time,
> ojaivalleybeefarm@dslextreme.com writes:
> Doug,
> What I'm thinking of now doing is instead of using an oil
> filled DC motor ( where you have the problem of the carbon from the
> brushes getting into the oil) is to use a AC induction motor and use an
> inverter from the DC batteries. There are water and oil filled AC
> motors out there which could probably be used. The inverters that they
> have now are very efficient. I just need to figure out what my battery
> capacity will be and go from there.
>
> Brian
>
>
> ----- Original Message -----
> From: DJACKSON99@aol.com
> To: personal_submersibles@psubs.org
> Sent: Thursday, November 16, 2006 01:30
> Subject: Re: [PSUBS-MAILIST] Oil Compensated Thursters
>
>
> Brian:
>
> My dad motivated me to stay in High School by putting me to work
> on Sanitary Sewer Systems (there is an oxymoron) and I serviced some
> lift station pumps. We used transformer oil in them.
>
> The engineer in your URL says "The lower efficiency carries about
> a 2% increase in overall energy costs." -- I'd like to see what that is
> based on, and does it pertain to low voltage motors too?
>
> And the water well pumps are often compensated with plain water.
> They just use wire in the winding that still has the insolation and
> stainless steel and plastic guts, but again these are high voltage.
>
> I suspect the efficiency may be really bad due to low voltage
> trying to cross through the oil. Perhapes I'll have to experiment on a
> smal DC motor to find the answer.
>
> The next question would then be, does 500 psi change the
> resistance of the connection between the brush and commuter in and oil
> compensated 24 to 36 volt DC Motor? What do you think?
>
> --Doug J
>
> In a message dated 11/16/2006 1:36:05 AM Central Standard Time,
> ojaivalleybeefarm@dslextreme.com writes:
> Doug,
> Do you think something like this would work? These
> are not DC however.
> http://www.zoeller.com/zep/techbrief/JF8article.htm
>
> Brian
> ----- Original Message -----
> From: DJACKSON99@aol.com
> To: personal_submersibles@psubs.org
> Sent: Wednesday, November 15, 2006 19:35
> Subject: [PSUBS-MAILIST] Oil Compensated Thursters
>
>
> Can anyone support this statement: "Scripps has tried to fill
> the DC motors with oil, but the oil gets between the brushes and the
> commutator, where the insulation properties of the oil causes problems.
> Although it would be possible to use high voltage to break through the
> oil film, the high voltage is a safety hazard for the divers."
> -- www.empiremagnetics.com/articles/deep_sea.htm
>
> I was thinking about 24 or 36 volt oil compensated brushed
> trolling motors, but after reading the above I looked and could not find
> any examples of oil compensated brushed motors under 100 volts.
>
> What are your experiences and thoughts?
>
> Thanks
> --Doug J
> http://www.submarineboat.com/
>
>
>
>
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