Technical, Techniques, Hints, and Tips > DC Motors (Brushed) and Speed Controllers

Speed controller questions

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BlueWotsit:
Couple of questions

1) Which of the following figures from a motors specifications should I look at for choosing a speed controllers size

Nominal voltage 9,6 V
Operating voltage range 7,2 ... 14,4 V
No-load speed 14600 min -1
No-load current drain 3,1 A
Current drain at max. efficiency 18 A
Stall current 120 A

2) When cooling a speed controller, what is the best method to use

thanks
Andrew

roycv:
Hi BW. sounds like you are running a pretty powerful motor!  Perhaps around 200 watts (10volts X 20 amps)  Most speed controllers will handle the voltage so it is the current and the enormous stall current which are the principle concerns.  Almost certainly run with a fuse of some sort.
If you can measure the current taken from the battery when driving the propeller in the water this will help a lot.  Choose a prop that runs as fast as possible without cavitating as the motor will be running more efficiently.  A rule of thumb here is to run the motor at 20% of the stall current which hits the best efficiency of most motors.

Cooling.
I cooled an Electronize ESC by simply making a plate the same size as the base plate and soldering 2 x 1/8th dia. brass tubes to it with a silicon flexible tube connecting 2 ends together and a small scoop at rear of prop, to pick up the water and an exit tube in side of boat.  Screw or attach the base plate to the ESC and use heat transmitting grease as the interface.

Connect together with flexible tubing and this cooled the ESC to pond water temperature when running at 15 amps and 12 volts (180 watts).  The batteries (5.1 Ah cyclons)  were almost too hot to handle.

Perhaps you can bear this in mind when choosing the ESC.

Hope this helps, regards Roy

BlueWotsit:
Hiya - forgot to mention the motor is a Graupner 700BB turbo 9.6v, and many thanks Roy

Fil:
Hi Andrew

What are you using the motor for, Scale models or Fast Electrics?

You must always consider the amps.  It is this that will cause the bigest problem to the motor and speed controller.  The higher resistance you create, ie poorly fitted prop shaft causing friction or a big propeller will cause the motor to draw more amps.  More amps more heat eventually things wont work anymore.

If you can tell me what the application is I can give you more specific advice.

The best way to cool a speed controller is to mount a heatsink to it and have this water cooled.

Phil

Stavros:
Bluewotsit just contact action man FLJ at Action he will put you right


Stavros(Just a very satisfied Customer)

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