<html><head></head><body><div style="color:#000; background-color:#fff; font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:16px"><div id="yui_3_16_0_ym19_1_1461703490009_2537"><span id="yui_3_16_0_ym19_1_1461703490009_2536">Hank,</span></div><div id="yui_3_16_0_ym19_1_1461703490009_2633" dir="ltr"><span id="yui_3_16_0_ym19_1_1461703490009_2632">another option is to change the propellers to a smaller diameter with</span></div><div id="yui_3_16_0_ym19_1_1461703490009_2631" dir="ltr"><span id="yui_3_16_0_ym19_1_1461703490009_2630">less pitch, so there is less load on the motor, if you can live with less speed!</span></div><div id="yui_3_16_0_ym19_1_1461703490009_2579" dir="ltr"><span id="yui_3_16_0_ym19_1_1461703490009_2580">As Steve said the manufacturer designed it for 120 V & unless you know</span></div><div id="yui_3_16_0_ym19_1_1461703490009_2611" dir="ltr"><span id="yui_3_16_0_ym19_1_1461703490009_2610">all the parameters it's difficult to know what you can get away with.</span></div><div id="yui_3_16_0_ym19_1_1461703490009_2613" dir="ltr"><span id="yui_3_16_0_ym19_1_1461703490009_2612">As an illustration of the complexity, a 120V electric raiser isn't as powerful as a 12V cordless drill!</span></div><div id="yui_3_16_0_ym19_1_1461703490009_2629" dir="ltr"><span>Cheers Alan</span></div><div class="qtdSeparateBR" id="yui_3_16_0_ym19_1_1461703490009_2538"><br><br></div><div class="yahoo_quoted" id="yui_3_16_0_ym19_1_1461703490009_2542" style="display: block;"> <div id="yui_3_16_0_ym19_1_1461703490009_2541" style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 16px;"> <div id="yui_3_16_0_ym19_1_1461703490009_2540" style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 16px;"> <div id="yui_3_16_0_ym19_1_1461703490009_2539" dir="ltr"> <font id="yui_3_16_0_ym19_1_1461703490009_2543" face="Arial" size="2"> <hr size="1" id="yui_3_16_0_ym19_1_1461703490009_2581"> <b><span style="font-weight: bold;">From:</span></b> hank pronk via Personal_Submersibles <personal_submersibles@psubs.org><br> <b><span style="font-weight: bold;">To:</span></b> Personal Submersibles General Discussion <personal_submersibles@psubs.org> <br> <b><span style="font-weight: bold;">Sent:</span></b> Wednesday, April 27, 2016 2:08 PM<br> <b><span style="font-weight: bold;">Subject:</span></b> Re: [PSUBS-MAILIST] power converter<br> </font> </div> <div class="y_msg_container" id="yui_3_16_0_ym19_1_1461703490009_2544"><br><div id="yiv5333154034"><div id="yui_3_16_0_ym19_1_1461703490009_2547"><div id="yui_3_16_0_ym19_1_1461703490009_2546" style="color: rgb(0, 0, 0); font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 12px; background-color: rgb(255, 255, 255);"><div id="yui_3_16_0_ym19_1_1461703490009_2548"><span>Hi Steve,</span></div><div id="yiv5333154034yui_3_16_0_ym19_1_1461722496625_3151"><span id="yui_3_16_0_ym19_1_1461703490009_2545">The motors have brushes, so I am going to do a test before I get to concerned. I can add a battery bank also as you mention to increase the voltage. I was planning something along that line anyways to increase my range. I need to add weight to offset the escape pod buoyancy, may as well be batteries.</span></div><div id="yiv5333154034yui_3_16_0_ym19_1_1461722496625_3151">Just a thought, what about running them on AC with a rectifier.</div><div id="yiv5333154034yui_3_16_0_ym19_1_1461722496625_3151">Hank</div> <div class="yiv5333154034qtdSeparateBR"><br clear="none"><br clear="none"></div><div class="yiv5333154034yahoo_quoted" id="yui_3_16_0_ym19_1_1461703490009_2555" style="display: block;"> <div id="yui_3_16_0_ym19_1_1461703490009_2554" style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 12px;"> <div id="yui_3_16_0_ym19_1_1461703490009_2553" style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 16px;"> <div class="yiv5333154034yqt6037251973" id="yiv5333154034yqt22165"><div id="yui_3_16_0_ym19_1_1461703490009_2649" dir="ltr"><font id="yui_3_16_0_ym19_1_1461703490009_2648" face="Arial" size="2"> On Tuesday, April 26, 2016 7:30 PM, Stephen Fordyce via Personal_Submersibles <personal_submersibles@psubs.org> wrote:<br clear="none"></font></div> <br clear="none"><br clear="none"> <div class="yiv5333154034y_msg_container" id="yui_3_16_0_ym19_1_1461703490009_2552"><div id="yiv5333154034"><div id="yui_3_16_0_ym19_1_1461703490009_2551"><div id="yui_3_16_0_ym19_1_1461703490009_2550" dir="ltr"><div>Hi Hank,</div><div id="yui_3_16_0_ym19_1_1461703490009_2556">I've dabbled a little bit in (small!) DC converters and my guess is that a converter that will do the current you're after will be expensive/large/complex and probably generate a significant amount of heat. Also seems like an obscure set of operating conditions that will be hard to find off the shelf. </div><div id="yui_3_16_0_ym19_1_1461703490009_2549"><br clear="none"></div><div>You've probably thought about it, but splitting the battery bank and rewiring part of it to supply 120VDC is probably the easiest low-tech solution if you have enough cells to put in series and achieve the higher voltage. You would get some nice redundancy there too if you have 2 battery banks controlling different thruster sets.</div><div><br clear="none"></div><div>As an aside, I suspect 48VDC is pretty lethal, but 120VDC even more so.</div><div><br clear="none"></div><div id="yui_3_16_0_ym19_1_1461703490009_2578">I just saw Alan's email come through - running it off lower voltage is definitely an option, but depends on the sort of motor. Ie. a brushed motor speed is proportional to the voltage applied (so running at 48VDC would give you less than half speed) - no idea what the Perry ones would be, but being older they may well be brushed. Brushless motor speed is proportional to frequency applied by the controller. In both cases torque is proportional to current which is proportional to heat generated. So the greater the current in your wires, the more heat needs to be dissipated, and if it's not then something will burn out - probably the thin layer of insulation on the motor windings. The trouble is dissipating the heat from the inner windings (it has to pass through the outer windings, which are producing their own heat) - but like Alan said, if you've got it oil compensated that will help a lot with heat dissipation. The thermal conductivity of oil is ~6x that of air (and water ~24x air), although the heat transfer is not quite as simple as that.</div><div><br clear="none"></div><div>I'm also pretty sure that the motor will have an inherent resistance that will be designed into it appropriate to the nominal voltage and current, and related to the size of the wires (ie. as Hank pointed out, thinner wires for high voltage as less current is required). So if you apply less voltage to the same resistance, it will draw less current - ie. I don't think you will be able to get extra current into the motor at lower voltage. Not quite that simple, but you get the idea.</div><div><br clear="none"></div><div>(that was mostly dredged up from memories of a university subject I did on electric motors a long time ago, feel free to correct me!)<br clear="none"><br clear="none"></div><div>Cheers,</div><div>Steve</div></div><div class="yiv5333154034gmail_extra" id="yui_3_16_0_ym19_1_1461703490009_2577"><br clear="none"><div class="yiv5333154034gmail_quote" id="yui_3_16_0_ym19_1_1461703490009_2576">On Wed, Apr 27, 2016 at 10:18 AM, hank pronk via Personal_Submersibles <span dir="ltr"><<a href="mailto:personal_submersibles@psubs.org" target="_blank" rel="nofollow" shape="rect" ymailto="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>></span> wrote:<br clear="none"><blockquote class="yiv5333154034gmail_quote" id="yui_3_16_0_ym19_1_1461703490009_2575" 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 class="yiv5333154034yqt6916798014" id="yiv5333154034yqt53876"><div id="yui_3_16_0_ym19_1_1461703490009_2574"><div id="yui_3_16_0_ym19_1_1461703490009_2573" style="color: rgb(0, 0, 0); font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 12px; background-color: rgb(255, 255, 255);"><div><span>Thanks" Kieth,</span></div><div dir="ltr"><span>I started to that but I have no idea if one system is better than another.</span></div><div dir="ltr"><span>Hank</span></div> <div><br clear="none"><br clear="none"></div><div id="yui_3_16_0_ym19_1_1461703490009_2572" style="display: block;"> <div id="yui_3_16_0_ym19_1_1461703490009_2571" style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 12px;"> <div id="yui_3_16_0_ym19_1_1461703490009_2570" style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 16px;"><div><div class="yiv5333154034h5"> <div dir="ltr"><font face="Arial" size="2"> On Tuesday, April 26, 2016 6:11 PM, k6fee via Personal_Submersibles <<a href="mailto:personal_submersibles@psubs.org" target="_blank" rel="nofollow" shape="rect" ymailto="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>> wrote:<br clear="none"></font></div> <br clear="none"><br clear="none"> </div></div><div id="yui_3_16_0_ym19_1_1461703490009_2569"><div id="yui_3_16_0_ym19_1_1461703490009_2568"><div class="yiv5333154034h5" id="yui_3_16_0_ym19_1_1461703490009_2567"><div id="yui_3_16_0_ym19_1_1461703490009_2566"><div id="yui_3_16_0_ym19_1_1461703490009_2565"><div>Hank,</div><div><br clear="none"></div><div>You want a dc-dc converter, just Google it.</div><div><br clear="none"></div><div>Keith T.</div><div><br clear="none"></div><div><br clear="none"></div><div><br clear="none"></div><div><div style="color: rgb(87, 87, 87); font-size: 85%;">Sent from my Verizon, Samsung Galaxy smartphone</div></div><div><br clear="none"></div><div id="yui_3_16_0_ym19_1_1461703490009_2564"><div id="yui_3_16_0_ym19_1_1461703490009_2563" style="color: rgb(0, 0, 0); font-size: 100%;"><div>-------- Original message --------</div><div>From: hank pronk via Personal_Submersibles <<a href="mailto:personal_submersibles@psubs.org" target="_blank" rel="nofollow" shape="rect" ymailto="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>> </div><div>Date: 4/26/16 4:53 PM (GMT-08:00) </div><div>To: Personal Submersibles General Discussion <<a href="mailto:personal_submersibles@psubs.org" target="_blank" rel="nofollow" shape="rect" ymailto="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>> </div><div id="yui_3_16_0_ym19_1_1461703490009_2562">Subject: [PSUBS-MAILIST] power converter </div><div><br clear="none"></div></div><div style="color: rgb(0, 0, 0); font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 12px; background-color: rgb(255, 255, 255);"><div>HELP,,,</div><div>Turns out my Perry thrusters are not 36V but 120 Vdc. I can only manage 48V dc from Gamma's battery bank. Can I step the voltage up with something.</div><div>Hank</div></div></div></div></div><br clear="none"></div></div><div>_______________________________________________<br clear="none">Personal_Submersibles mailing list<br clear="none"><a href="mailto:Personal_Submersibles@psubs.org" target="_blank" rel="nofollow" shape="rect" ymailto="mailto:Personal_Submersibles@psubs.org">Personal_Submersibles@psubs.org</a><br clear="none"><a href="http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles" target="_blank" rel="nofollow" shape="rect">http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles</a><br clear="none"></div><br clear="none"><br clear="none"></div> </div> </div> </div></div></div></div><br clear="none">_______________________________________________<br clear="none">
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