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enter image description here I'm trying to simulate the following chopper controlled dc motor in MATLAB Simulink using a PI controller. Now without the freewheeling/flyback diode across the motor terminals I can simulate the model to get the desired speed output. But with the diode the motor seems to run at full speed and is uncontrollabe. Is it a glitch in the software? or is there anything I can do about it in the software?

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    \$\begingroup\$ When you see something unexpected then for sure it must be a bug in the software. It cannot be that anything unexpected is happening in your design, or can it? You're using models of components. Do be aware of this statement about models: "All models are wrong, but some are useful". I suggest that you investigate what is happening precisely. Why does the diode influence behavior when it should not. Why should the diode not influence the behavior? Hint: it should be operating in.... Is it operating like that or not? \$\endgroup\$ – Bimpelrekkie Apr 20 at 13:19
  • \$\begingroup\$ A doubt if we use a flyback diode won't the motor experience a breaking torque during pwm off period? Is that desirable? \$\endgroup\$ – ASWIN VENU Apr 20 at 13:53
  • \$\begingroup\$ I would look carefully at how the diode is modeled. It sounds like ti is acting like something other than a normal diode. \$\endgroup\$ – Charles Cowie Apr 20 at 16:44

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