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Old Mar 12, 2009, 06:13 PM
leybold12 is offline
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USA, AZ, Tucson
Joined Aug 2008
42 Posts
Huge jump in no load current

Okay, I know this isn't RC exactly, but I am experimenting with RC brushless motors as a substitute in industrial applications. This might apply to motor construction.

I have a Turnigy SK 63-64-230kv outrunner running off 37 volts. I am driving it with a Sentilon HV-100A esc. Without load, I draw approximately 2 amps as my Io/no load current. I mount the motor in an adapter so the motor can mounted inside a tool. I made the adapter out of copper pipe (cheap, easy to machine, good heat transfer, easy to braze). See photo below.

Now when I turn on the motor, the no load current at full rpm is close to 5 amps. When I shut off the throttle, the motor now stops like the brake is on (it is off). In 15 seconds the copper adapter becomes too hot to touch. The copper around the rotor (about 0.1 inch air gap) gets hot very quickly as if the copper is being heated by induction. I had thought that I would not have inductive heating since I used copper.

I tried it with an Towerpro 5330-10T. The no load current jumped from 2.6 amps to 5.8 amps. I tried it with a Scorpion HK4035-560 which leaves a 0.5 inch air gap between the rotor and the copper and there was no increase in no load current.

Any idea what is going on?

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Last edited by leybold12; Mar 12, 2009 at 06:30 PM.
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