Motor Physics

Lorentz Force

Current in magnetic field creates a force

$$F=i \int_{W} dl \times B=I\times B$$

In DC Motors, our torque $\tau \propto I$.

Faraday's Law

$$\oint_{\partial \Sigma} E \cdot dl=-\frac{d}{dt} \iint_{\Sigma}B \cdot dA$$

Back EMF

$$V_E=-\frac{d}{dt} \Phi_B$$

The Back EMF $V_E \propto \omega$, where $\omega$ is the angularity speed.

Important Relationship in DC Motors

An important relationship existing in DC Motors

Analysis

Analysis

When a motor , its current draw is: Maximum.

Why?

As you can see, when motor stalls, the output torque is very very large and reaches the maximum. Since $\tau \propto I$, we can say that our current draw is maximum.