motorconstante

Motorconstante, or motor constant, is a key parameter of electric motors that links electrical input to mechanical output. In practice it refers to two related constants: the torque constant Kt, which relates torque T to current I through T = Kt · I, and the back-EMF constant Ke, which relates generated back-emf E to angular velocity ω through E = Ke · ω. Together they describe how efficiently a motor converts electrical power into rotation and how it behaves in steady state and during transients.

Units and relationships. In SI units, if Ke is expressed as volt per (rad/s) and Kt as newton-meters per ampere, Kt and Ke are numerically equal (Kt = Ke). If Kv is given as revolts per volt (rpm/V), then Kt = 9.5493 / Kv. Equivalently, Kv = 1/Ke when单位 conversions are applied. These relationships underpin how motor performance is modeled and controlled.

Measurement and use. To determine Kt, one can measure the stall torque produced by a known current, or the torque at a given operating current. To determine Ke, measure the back-emf at a known speed, or determine Kv from no-load speed at a given supply voltage and compute Kt from Kv. The motor constant is essential in motor selection, drive design, and dynamic modeling for DC motors, brushless DC motors, and stepper motors. It influences torque and speed limits, efficiency, and control stability.

Limitations. In practice, Kt and Ke vary with temperature, magnetic saturation, winding resistance, and load conditions. They are most reliable near the motor’s rated operating point. Temperature compensation and compensation for nonlinearities are common in precision applications.