[PSUBS-MAILIST] Brushless Thrusters

Wed Sep 10 12:03:01 EDT 2014

Only that higher voltages present more risk, particularly in DC systems, so you need to take particular care to keep everything protected from stray hands, tools and debris. A high voltage DC short will wake you up in a hurry. Isolation is a must (no hull connection to battery negative).

 Also, when you add cells in series to raise the DC voltage of your battery bank, you don't also increase capacity, only voltage. Only cells (or banks) in parallel will add Amp hours, so you're looking at lots of batteries for a high voltage system.

IIRC, ABS will consider systems to 600 V. You need 690 VDC if you want to run true industrial motors (440V) via VFD, but if you can source lower voltage AC motors, there's no reason you couldn't do this, if it was cost effective for you. A 48V AC motor would need 68 VDC to the VFD bus.

Sean

On September 10, 2014 9:07:29 AM MDT, Brian Cox via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>Sean,   Is there any reason why not to run the higher voltage if you
>want to run one of these AC motors for a sub ?   I'm going to have to
>make some decisions on my motors soon.  The higher voltages are more
>efficient .
>
> 
>
>Brian
>
>--- personal_submersibles at psubs.org wrote:
>
>From: "Sean T. Stevenson via Personal_Submersibles"
><personal_submersibles at psubs.org>
>To: Personal Submersibles General Discussion
><personal_submersibles at psubs.org>
>Subject: Re: [PSUBS-MAILIST] Brushless Thrusters
>Date: Wed, 10 Sep 2014 05:53:12 -0600
>
>AC induction motors can run off a VFD with the DC bus directly supplied
>- in this case, you only need the inverter stage and not the rectifier
>stage of the VFD, but there are caveats: the DC bus connections must be
>available (rare in small VFDs), and the bus voltage must be high
>(sqrt(2)×nominal motor voltage). This would require either a battery
>bank offering hundreds of volts DC, or some sort of DC-DC converter to
>step up the DC voltage into the VFD bus.
>
>Sean
>
>
>On September 10, 2014 4:04:59 AM MDT, Alan via Personal_Submersibles
><personal_submersibles at psubs.org> wrote:
>
>Hi Brian,
>
>I don't know a lot about them, but I believe you can't run them off DC
>
>& they are generally heavyweight industrial units.
>
>Alan
>
>Sent from my iPad
>
>
>On 9/09/2014, at 10:48 pm, Brian Cox via Personal_Submersibles
><personal_submersibles at psubs.org> wrote:
>
>Why not just use an AC induction motor then?  
>
>--- personal_submersibles at psubs.org wrote:
>
>From: Alan via Personal_Submersibles <personal_submersibles at psubs.org>
>To: Personal Submersibles General Discussion
><personal_submersibles at psubs.org>
>Subject: Re: [PSUBS-MAILIST] Brushless Thrusters
>Date: Tue, 9 Sep 2014 22:24:04 +0700
>
>Hi Alec,
>
>not sure what motivated me down this path, but eventually it will add
>more to the psub
>
>knowledge pool.
>
>The brushless motors are used successfully on a lot of rovs & expensive
>submersibles,
>
>so I assume the pros out way the cons. Just a matter of learning how to
>put together
>
>a good package. The Haswing Protruar brushless Chinese trolling motor
>that Emile uses
>
>was a very cheap unit. I made enquiries a few years ago & they offered
>me an ex factory 
>
>sample thruster for I think a couple of hundred dollars. 
>
>The motors I'm looking at are used on model trucks for racing on short
>courses; so should be able to wind them up quickly. One problem is that
>a lot of motor controllers for them
>
>don't have reverse.
>
>The motors are so small, you could probably use a standard peice of
>aluminium pipe
>
>to house them, &! amp; machine the propellor shaft & bearing housing
>end out of a solid tube of
>
>aluminium.  
>
>Alan
>Sent from my iPad
>
>
>On 9/09/2014, at 8:30 pm, Alec Smyth via Personal_Submersibles
><personal_submersibles at psubs.org> wrote:
>
>That is remarkable power for the size, very interesting for that reason
>alone. But it seems to me like quite a challenge to adapt as a
>thruster. I recall Emile's comment that the high-RPM Chinese brushless
>trolling motor he was using required something like ten seconds to wind
>up when you gave it juice. The efficiency makes it great for surface
>runs but not useful for submerged maneuvering. You might have the same
>issue with this if you need to gear it down.
>
>
>Best,
>
>
>Alec
>
>
>On Tue, Sep 9, 2014 at 12:35 AM, Alan via Personal_Submersibles !
><personal_submersibles at psubs.org> wrote:
>
>Update,
>
>Am still Googling away in pursuit of a home made brushless thruster.
>
>I am set on using an in-runner motor as they have the coils on the
>outside & will be able
>
>to transfer heat through the can.
>
>The problem with in-runners is they have higher revs than out-runners,
>however either will 
>
>require a planetary gearbox. I am looking at reducing the revs down to
>below 3000 rpm. 
>
>This is based on other brushless thrusters I have looked at but might
>not be right ( any recommendations)?
>
>Another problem is that most seem to draw huge amps.
>
>Here is a 1200W motor for $30-. Of course there is the price of the
>contr! oller & planetary gear that are needed.
>
>http://www.hobbyking.co.uk/mobile/viewproduct.asp?idproduct=17720&type=&idparentcat=364
>
>Most of the suitable motors seem to be found at places like Hobby King,
>and are used on RC trucks, or found on E bike sights. The aircraft
>motors aren't as robust.
>
>These motors are tiny, but hugely powerful, so there is the potential
>to make a small streamlined
>
>powerful unit.
>
>I haven't had much luck with a matching gearbox. Some of the planetary
>gearboxes recommend
>
>oiling (no good to me unless I oil compensate) while others don't. I am
>looking for a cylindrical unit to match my motor, preferably with
>thrust bearings.
>
>If anyones got any advice or experience in this realm I'd be pleased to
>hear it.
>
>Regards Alan
>
>
>! 
>
>
>Sent from my iPad
>
>
>On 7/09/2014, at 8:43 pm, Alan via Personal_Submersibles
><personal_submersibles at psubs.org> wrote:
>
>Hi Hank,
>
>the kort nozzle on the Indonesian thruster looks a bit Naff. 
>
>( I am designing an art work here.)
>
>I could get a price for the unit without kort nozzle, but
>
>I'm wondering if I could build something for 1/2 that price.
>
>There are some reasonably priced brushless motors about.
>
>I don't know that I could just retro fit a thrust bearing inside the
>can of the motor.
>
>I tried to put a thrust bearing for reverse inside my brushed
>thrusters, but
>
>couldn't find one with a thin enough section to fit.
>
>Also the motors are a bit expensive to just buy & hope you can fit one.
>
>How did you fit the thrust bearing on Gamma?  Did the propell! or shaft
>extend out the back
>
>of the motor?
>
>Alan
>
>
>
>Sent from my iPad
>
>
>On 7/09/2014, at 7:22 pm, hank pronk via Personal_Submersibles
><personal_submersibles at psubs.org> wrote:
>
>Allan
>Dont worry about thrust bearings to much. They are aesy to get, I
>bought one for Gamma , real heavy duty for 80 dollars. Personally I
>would just use a good quality bearing and replace it once a year for 8
>bucks, if it is a small thruster. Are you not happy with the Indonesia
>thrusters? Or to pricey?
>Hank
>
>
>_____________________________________________
>From: Alan via Personal_Submersibles <personal_submersibles at psubs.org>;
>
>To: Personal Submersibles General Discussion
><personal_submersibles at psubs.org>; 
>Subject: [PSUBS-MAILIST] Brushless Thrusters 
>Sent: Sun, Sep 7, 2014 11:58:56 AM 
>
>Hi people,
>I've spent several hours today looking at brushless thrusters & wonder
>if anyone else has looked at them or got any ideas. There is the
>Indonesian thruster I posted a few weeks back at US 2,200. There is
>also the Haswing Protruar 2hp that Emile has; however they state that
>it's for fresh water only, & I think Emile said it was a bit noisy.
>The inrunner motors that have the winding on the outside, seem a good
>option as they cool through convection to the can. They also need
>higher revs for torque & require a planetary gear box or similar. (
>which a lot have built in)
>I was looking at the option of making my own thruster, however the
>motor would require a thrust bearing & I don't
>know of any that would have one other than maybe a high powered battery
>operated drill.
>Any thoughts, suggestions thanks.
>Alan
>
>Sent from my iPad
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>-- 
>Sent from Kaiten Mail. Please excuse my
>brevity._______________________________________________
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