Consider the following DC motor parameters:

  • Rotor resistance, $R\ [\Omega]$
  • Motor constant, $k_t\ [\mathrm{V/rpm}]$
  • Inertia, $I\ [\mathrm{kg\cdot m^2]}$

How do they scale with motor size? Do $R$ and $k_t$ depend on $I$?

  • 1
    $\begingroup$ There are no answers to this as there are considerably more factors to consider in specifying a motor than those listed here. $\endgroup$
    – welf
    Commented Jul 22, 2018 at 12:33

1 Answer 1


Your described motor constant = peak voltage / rotational speed under no load. The latter decreases if your motor resistance increases. Inertia is obviously going to increase with a thicker shaft.


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