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Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
Hi, is there any problem with using say, 20 kHz drive frequency, for a single-switch step down controller running a dc permanent magnet motor directly (without any LC filter)? As I understand it, the hysteresis and eddy current losses shouldn't increase with frequency if the drive voltage isn't increased, is this right?
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
Well, it might do something, but don't try it with your brand new DeWalt as the risk of blowing up the drill would be high! :/ There's also a freewheel diode across the motor that would have to be removed, as it would kill the flyback spikes. These are unwanted in a motor drive but kind of important for driving a flyback.
Most cordless drills I've used make an audible squeal, implying the frequency is nearer 2kHz than 20, so try an ignition coil instead
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DC motor control with high frequency pwm
