What’s the relationship between torque and current, and voltage and speed applied to a motor?

Featuring Philipp Betschart, Design Engineer.

In Alva SlimTorq™ motors, torque is created by the interaction between the rotor’s permanent magnets and the stator’s electromagnetic field. Because the rotor field is fixed, torque depends entirely on how we control the electromagnetic field in the stator by altering the current. So, torque is directly proportional to current. Now, as the rotor spins, it induces something called back electromotive force (back EMF) — an opposing voltage in the stator windings. This back EMF increases with speed. To reach higher speeds, we need to overcome this back EMF by applying a higher voltage. So, speed is proportional to voltage.

In short:

• More current → More torque
• Higher voltage → Higher speed
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