# How do DC motor parameters scale with motor size?

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 $I$?

• There are no answers to this as there are considerably more factors to consider in specifying a motor than those listed here. – welf Jul 22 '18 at 12:33

## 1 Answer

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.