Re: 4Q Motor control paradox

Roger wrote:
BTW, not bored....just been looking at an old chopper cct that I used
in the past and am thinking of using again and I wondered why I need
the braking resistors.

If you have a low resistance motor, which limits its current
by generating back EMF, then when you short it (perhaps by
switching on both your fat low-side MOSFETs), you get very
rapid braking and your MOSFETs, wiring or motor go pop.

If you want to regenerate into the power supply, you short
the motor until the current builds (based on L/R) to a
predetermined level, then you quickly switch, steering that
current into the supply until it drops again. Rinse and
repeat for amount of the braking you want.
.

Relevant Pages

  • Re: 4Q Motor control paradox
    ... the braking resistors. ... If you have a low resistance motor, ... switching on both your fat low-side MOSFETs), ... rapid braking and your MOSFETs, ...
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  • Re: ON topic- More Y-axis OverVoltage- Random consistentcy frustration
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  • Re: Why do electric powered automobiles need to be so complicated?
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  • Re: DC Motor Driver Regenerative Braking
    ... The concept is that you use one of the appropriate switches and one clamp diode to short the motor, briefly, using its self generated EMF to drive the current up to the magnitude that produces the desired braking torque, then open the switch and let the motor inductance pump that current into the supply through the clamp diodes, like a flyback power supply would. ... Letting the current wind all the way to zero reduces the switching losses for the next shorting part of the cycle, but lowers the average braking torque relative to the peak current, so the peaks have to be higher to get the same average breaking. ...
    (sci.electronics.design)