tilbakeEMF

TilbakeEMF, also known as back electromotive force, is the electromotive force generated in a conductor or electrical machine when its magnetic environment changes, such as when windings rotate within a magnetic field. It arises from Faraday's law of induction and follows Lenz's law: the induced voltage opposes the change in current that produced it. In rotating machines, the back EMF is typically proportional to the speed of rotation and can be represented as E = k_e ω, where k_e is a machine constant and ω is angular velocity.

In direct current motors, back EMF increases with speed, naturally limiting the current drawn from the supply as the motor accelerates. The terminal voltage and current are related by V = E + I R, where R is the winding resistance. This negative feedback helps stabilize motor speed and reduces power draw at higher speeds. Conversely, if the motor is driven as a generator, rotation induces an EMF proportional to speed, which can supply power back to the circuit or be used for speed sensing.

Back EMF is also exploited in sensorless motor control, where the EMF observed in undriven phases serves as a reference for estimating rotor position and speed. In circuit design, back EMF can cause voltage spikes when switching inductive loads; suppression methods include flyback diodes, snubber networks, RC dampers, and transient voltage suppressors to protect components.

Overall, tilbakeEMF is a fundamental phenomenon in motors and inductive systems, influencing performance, efficiency, control strategies, and protection requirements.