[PSUBS-MAILIST] Brushless thruster test 2

[Alan James via Personal_Submersibles]

      From: Alan James <alanlindsayjames at yahoo.com>
 To: Personal Submersibles General Discussion <seaquestor at gmail.com> 
 Sent: Saturday, February 6, 2016 11:18 PM
 Subject: Brushless thruster test 2
   
This is mainly for Cliff's benefit, as he is going to be doing somethrust testing.Tested 2 different props out. One being the same as the first test, the yamaha 7&1/4" x 4" pitch & the second was a Vetus 6 blade 108 mm ( 4")  for 25kg bow thruster. No stats on the pitch but itlooks about 180mm or 7".My watts measurement is done off the battery whereas other people quote their output at the motor.I am comparing my motors performance to statistics from commercial thruster brands but not surewhere they are measuring there power from.Had some wacky results from the yamaha prop again. It was the more powerful & I think I am getting whatis called a "short circuit" effect through having the motor about 28" out from the pool edge & in about 3ftof water. Short circuit is where an edi is formed & the water moves from the output to the input in a semicircle around the thruster. This is caused by water bouncing off a pool wall, or in my case the inlet flow bouncing off the wall or pool bottom.I was running off a 40V 5 amp  Lipo battery & the voltage dropped a bit during the tests.Ist test was 10 kg (22 lb ) at 500 W 2nd 11 kg at 1000 W & 39 V3rd 15 kg at a huge 3,400 W4th 37 kg at 3,800 W & 85 amps.As you can see some inconsistent results there, and some missing figures like amp draw, as I neededan assistant to read the figures.Next is the Vetus prop.1st 10kg  547 W  39 V2nd 11 kg  634 W  11 amps  37.81 V3rd  15 kg  998 W  27 amps4th  20 kg  1700 W  39 V5th  24 kg  2500 WIt's amazing what a difference a prop makes.In conclusion, I need to ditch this rig & buy a longer plank of wood to do tests in the middle of the deep end.I have a more sophisticated volt / amp meter that stores results & plots on a computer & I need to employ that.I need to buy a similar motor but a sensored version, as there was too much cogging at low speed.Sensoreless motors read the back emf produced by the motor to ascertain the position of the rotors & can stop /start
& rotate backwards on low speed where there isn't enough back emf produced.I need to replace my motor controller with a sensored controller, probably Kelly & buy a bigger life po4 battery.
   I also want to wire the motor to a WYE configuration which will give me .73 less rpm. So will gear it down a bit.Some good news is I have found people on boating forums adapting these RC brushless motors & an absoluteguru who uses these motors for traction vehicles & has posted pages of information on them.Cheers Alan




  
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