[PSUBS-MAILIST] Thruster Test

[Alan via Personal_Submersibles]

Hi all,
Bolted my brushless thruster on a Minn kotta outboard bracket & took
it for a run on the back of my inflatable yesterday.
Photo shows 48V battery pack in battery box, with an oil compensator, speed
controller in plastic box & red servo tester ( speed input ) on top of it.
The servo tester is wired to the speed controller & turns the pot input into a 2.4ghz signal. I knew this would be the weak link as it was a cheap unit that I had
previously had trouble with. Possibly the loose pin connection in to it.
I had trouble from the start & swapped to my backup which was a radio control
transmitter & receiver. 
I was running the brushless motor on sensorless mode. This means the commutation
is sequenced based on position feedback from the motors back emf.
This wasn't working well on high speeds & was jumpy or stopping completely
as it lost it's sequence. All my motors (11) have hall sensors for sensored control
but I had problems setting that up in the computer program so ran without it
as I wanted to get on the water. The speed controller operates on both so the
"not so good" sensorless control is a back up if a sensor fails.
Speed controller temperature got up to 75C, it has an over temperature function
that backs off the power at 80C, so I stopped to let it cool. I did have heat sinks
glued to the top of my battery box to mount the controller on, but when I set up
at the beach I found I couldn't reach that position as the wires weren't long 
enough :( . Highly recommend that any motor controllers have good heat sinks
or are heat sinked to the hull as it will increase their life or save them from failing.
Was followed by a small stingray for a while so am thinking the motor may put out
an attractive vibration to them!
The thrust was good & I am intending to have 4 horizontal thrusters, so should
speed along.
A few things to work on before my next outing.
Alan
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