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[Sheaffy]

Hi there, bit of a newbie to ESC's Need some advice on what AMP rating to get for the current setup any and all help is appreciated.


Had a 160A ESC however it fizzed on me and threw out lots of white smoke.

Prop -> Graupner Jet Propulsion Unit 5 (2347) (G2347) Flange Diameter: 78mm Shaft Diameter 7mm http://www.cornwallmodelboats.co.uk/acatalog/graupner_2347.html

Motor -> Graupner HPD 2948-3760 7.4V Brushless Motor
Operating voltage range : 7,4... 24 V
All-up weight, approx. : 180 g
Free shaft length: 10 mm
Output : 2000 W
Number of poles: 4
Permissible motor direction : R und L
Case length: 58,2 mm
Shaft diameter: 4 mm
Max. charging rate: 105 A
Case diameter: 29 mm
Revolutions/Volt: 3760
Part No: G7757
http://www.cornwallmodelboats.co.uk/acatalog/G7757.html

Battery ------- 7.4v 2s 40c 5600mah

Boat -> Weight: will be 8 Kilos once equipment fitted. currently around 5 kilos. length:1.3m


link to the ESC that blew. https://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=45159

I hope that this information is suitable and can help with my question. many thanks Ashley


Could you increase you Font size please

ken

[triumphjon]

do you know what size impelor your jet drive is running < it could be that your motor is simply too powerful , and not producing thrust , just cavitation . i had a similar fate to a jet drive im using in a huntsman 31 hull , the jet drive is a kmb 28 , which when i purchased the drive unit it was fitted with a 3700kv motor , this has now been replaced with an overlander 2100kv motor & running on a 7.4 v lipo im getting sensible scale like speeds and decent run times , its now using an 80 amp esc 9 100 blow ) you can use aircraft type esc as the jet drives wont pump backwards

[Sheaffy]

Thanks for the reply, the boat was working and producing considerable thrust. for around 8-9 minutes, then fuzzed out.....


we had the esc set to 50% output anyway. so there shouldn't be too much of a problem. its a big boat, all fibreglass custom built.
and houses electrical equipment so weighs a fair bit too.


after the research i did, i concluded that the 160A ESC should be enough, however after looking at some equations, this may help?


the motor is 2000W and running at 7.4v..
so acording to the equation, it should be 270A? or have i got this wrong? this is on the assumtion that it uses the full 2000W of power.

DC watts to amps calculation
The current I in amps (A) is equal to the power P in watts (W), divided by the voltage V in volts (V):

[inertia]

Ah! - the "Chinese amps" paradox. If your calculations are correct then you would need a speed controller capable of handling 270A continuously. There are numerous such creatures on E-Bay BUT my own calculation, allowing for 1% loss and a cable length of only 0.25m, is that for such a voltage and current the ESC and battery pack need to be fitted with 6 AWG cable. That's 5/16" diameter (7.5mm). You will be lucky to find one with cable thicker than 14AWG - which is good for around 32A. I don't suppose your now-defunct '160A' ESC had any more than that fitted, did it?
The fact that you had the thing set at 50% indicates that the power of the motor was too great on full power, and an ESC works a lot harder switching the voltage on and off to produce 50% power than it does when running at 100% i.e. voltage is switched on all the time.
I reckon John is right - a 3700kv motor is just too fast to produce anything useful in that particular waterjet. I'd follow his suggestion about motor size, battery voltage and using an aircraft ESC. I would also suggest including a cheaper watt-meter in the circuit to record the actual maximum current and power during a run - that's in proper European amps!  http://www.componentshop.co.uk/150a-watt-meter-and-power-analyser.html
DM

[Sheaffy]

Hi i set the ESC to 50% because it was our first run with the boat and did not want to over do it.
This wasn't because we thought it would be too much.


we would like it to still have water cooling and a BEC for the servos, i hope that the case is that the motor is still okay to use, as it was quite pricy and well outside of the returns policy.


I just want the damn boat working haha.