Читать книгу Analysis and Control of Electric Drives - Ned Mohan - Страница 57

Equation (2-43) shows that the electromagnetic torque required from the motor to accelerate a motor‐load combination depends on the gear ratio. In a basically inertial load where T_L can be assumed to be negligible, T_em can be minimized, for a given load‐acceleration , by selecting an optimum gear ratio (r₁/r₂)_opt.. The derivation of the optimum gear ratio shows that the load inertia “seen” by the motor should equal the motor inertia, that is, in Eq. (2-44),

(2-45a)

and, consequently,

(2-45b)

With the optimum gear ratio, in Eq. (2-43), using T_L = 0, and using Eq. (2-41),

(2-46)

Similar calculations can be made for other types of coupling mechanisms (see homework problems).