<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8" /></head><body dir="auto"><p dir="ltr">One advantage of AC induction motors is that you can decrease the nominal speed by increasing the number of poles in the motor winding.</p>
<p dir="ltr">For example, a 2 pole motor rated for 60 Hz (US & Canada), has a synchronous speed of 3600 rpm. By using a 4 pole winding instead, you decrease the synchronous speed to 1800 rpm, 1200 rpm for a 6 pole winding, and so forth.</p>
<p dir="ltr">Note that the synchronous speed is somewhat irrelevant if you are using a VFD, since the motor speed is controlled by varying the inverter frequency; however, efficiency takes a hit if you are operating much below half of the rated synchronous speed, so for the same target rpm you are better off using a motor with a greater number of poles with the VFD operating closer to the synchronous speed, versus dialing the VFD way down on a faster motor.</p>
<p dir="ltr">Sean<br>
</p>
<br><br><div class="gmail_quote">On September 10, 2014 4:49:48 PM MDT, Alan via Personal_Submersibles <personal_submersibles@psubs.org> wrote:<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">
<div>Thanks Brian & Sean,</div><div>those motors are a bit big for me. </div><div>I'm looking round the 1000W range & trying to keep the revs</div><div>below 3000 rpm.</div><div>Alan<br /><br />Sent from my iPad</div><div><br />On 10/09/2014, at 10:07 pm, Brian Cox via Personal_Submersibles <<a href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>> wrote:<br /><br /></div><blockquote type="cite"><div><div style="font-family:Arial, sans-serif; font-size:10pt;"><div>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 .</div><div> </div><div>Brian<br /><br />--- <a href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a> wrote:<br /><br />From: "Sean T. Stevenson via Personal_Submersibles" <<a
href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>><br />To: Personal Submersibles General Discussion <<a href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>><br />Subject: Re: [PSUBS-MAILIST] Brushless Thrusters<br />Date: Wed, 10 Sep 2014 05:53:12 -0600<br /><br /></div><p dir="ltr">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.</p></div>
<p dir="ltr">Sean<br />
<br /><br /></p><div>On September 10, 2014 4:04:59 AM MDT, Alan via Personal_Submersibles <<a href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>> wrote:<blockquote style="margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex; border-left-color: rgb(204, 204, 204); border-left-width: 1px; border-left-style: solid;">
<div>Hi Brian,</div><div>I don't know a lot about them, but I believe you can't run them off DC</div><div>& they are generally heavyweight industrial units.</div><div>Alan<br /><br />Sent from my iPad</div><div><br />On 9/09/2014, at 10:48 pm, Brian Cox via Personal_Submersibles <<a href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>> wrote:<br /><br /></div><blockquote><div><div style="font-family: Arial, sans-serif; font-size: 10pt;">Why not just use an AC induction motor then? <br /><br />--- <a href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a> wrote:<br /><br />From: Alan via Personal_Submersibles <<a href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>><br />To: Personal Submersibles General Discussion <<a href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>><br />Subject: Re: [PSUBS-MAILIST] Brushless Thrusters<br />Date:
Tue, 9 Sep 2014 22:24:04 +0700<br /><br /><div>Hi Alec,</div><div>not sure what motivated me down this path, but eventually it will add more to the psub</div><div>knowledge pool.</div><div>The brushless motors are used successfully on a lot of rovs & expensive submersibles,</div><div>so I assume the pros out way the cons. Just a matter of learning how to put together</div><div>a good package. The Haswing Protruar brushless Chinese trolling motor that Emile uses</div><div>was a very cheap unit. I made enquiries a few years ago & they offered me an ex factory </div><div>sample thruster for I think a couple of hundred dollars. </div><div>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</div><div>don't have reverse.</div><div>The motors are so small, you could probably use a standard peice of aluminium pipe</div><div>to house them, &!
amp;
machine the propellor shaft & bearing housing end out of a solid tube of</div><div>aluminium. </div><div>Alan<br />Sent from my iPad</div><div><br />On 9/09/2014, at 8:30 pm, Alec Smyth via Personal_Submersibles <<a href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>> wrote:<br /><br /></div><blockquote><div><div dir="ltr">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.<div><br /></div><div>Best,</div><div><br />Alec</div></div><div><br /><div>On Tue, Sep 9, 2014 at 12:35 AM, Alan via Personal_Submersibles <span dir="ltr">!
<<a href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>></span> wrote:<br /><blockquote style="margin: 0px 0px 0px 0.8ex; padding-left: 1ex; border-left-color: rgb(204, 204, 204); border-left-width: 1px; border-left-style: solid;"><div dir="auto"><div>Update,</div><div>Am still Googling away in pursuit of a home made brushless thruster.</div><div>I am set on using an in-runner motor as they have the coils on the outside & will be able</div><div>to transfer heat through the can.</div><div>The problem with in-runners is they have higher revs than out-runners, however either will </div><div>require a planetary gearbox. I am looking at reducing the revs down to below 3000 rpm. </div><div>This is based on other brushless thrusters I have looked at but might not be right ( any recommendations)?</div><div>Another problem is that most seem to draw huge amps.</div><div>Here is a 1200W motor for $30-. Of course there is the price of the
contr!
oller
& planetary gear that are needed.</div><div><span><a href="http://www.hobbyking.co.uk/mobile/viewproduct.asp?idproduct=17720&type=&idparentcat=364">http://www.hobbyking.co.uk/mobile/viewproduct.asp?idproduct=17720&type=&idparentcat=364</a></span></div><div><span>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.</span></div><div>These motors are tiny, but hugely powerful, so there is the potential to make a small streamlined</div><div>powerful unit.</div><div>I haven't had much luck with a matching gearbox. Some of the planetary gearboxes recommend</div><div>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.</div><div>If anyones got any advice or experience in this realm I'd be pleased to hear it.</div><div>Regards Alan</div><div><br /></div>!
<div><br />Sent from my iPad</div><div><div><div><br />On 7/09/2014, at 8:43 pm, Alan via Personal_Submersibles <<a href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>> wrote:<br /><br /></div><blockquote><div><div>Hi Hank,</div><div>the kort nozzle on the Indonesian thruster looks a bit Naff. </div><div>( I am designing an art work here.)</div><div>I could get a price for the unit without kort nozzle, but</div><div>I'm wondering if I could build something for 1/2 that price.</div><div>There are some reasonably priced brushless motors about.</div><div>I don't know that I could just retro fit a thrust bearing inside the can of the motor.</div><div>I tried to put a thrust bearing for reverse inside my brushed thrusters, but</div><div>couldn't find one with a thin enough section to fit.</div><div>Also the motors are a bit expensive to just buy & hope you can fit one.</div><div>How did you fit the thrust bearing on Gamma? Did the
propell!
or shaft
extend out the back</div><div>of the motor?</div><div>Alan</div><div><br /><br />Sent from my iPad</div><div><br />On 7/09/2014, at 7:22 pm, hank pronk via Personal_Submersibles <<a href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>> wrote:<br /><br /></div><blockquote><div><table border="0" cellspacing="0" cellpadding="0"><tbody><tr><td valign="top"><div>Allan<br />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?<br />Hank</div></td></tr></tbody></table> <div>
<div>
<br />
<div>
<div style="font-size: 0.9em;">
</div></div></div></div></div></blockquote></div></blockquote></div></div></div></blockquote></div></div></div></blockquote></div></div></blockquote></blockquote></div><p></p><hr size="1" />
<b>
<span style="font-weight: bold;">From:</span>
</b>
Alan via Personal_Submersibles <<a href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>>; <br />
<b>
<span style="font-weight: bold;">To:</span>
</b>
Personal Submersibles General Discussion <<a href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>>; <br />
<b>
<span style="font-weight: bold;">Subject:</span>
</b>
[PSUBS-MAILIST] Brushless Thrusters <br />
<b>
<span style="font-weight: bold;">Sent:</span>
</b>
Sun, Sep 7, 2014 11:58:56 AM <br />
<br />
<table border="0" cellspacing="0" cellpadding="0"><tbody><tr><td valign="top">Hi people,<br />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.<br />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)<br /> I was looking at the option of making my own thruster, however the motor would require a thrust bearing & I don't<br />know of any that would have one other than maybe a high powered battery operated drill.<br />Any thoughts, suggestions thanks.<br />Alan<br /><br
/>Sent from my
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