Controller by dc servo motor speed formula shows that there are three basic modes of speed regulation of dc motor controller, namely, adjustable resistance R, regulate the armature voltage U and adjust the value of magnetic flux Ф. But the armature resistance speed economy, and speed range is limited, rarely used. (1)In regulating the armature voltage, if I keep the armature current is constant current, the magnetic flux Ф remains the same, by the known, electromagnetic torque motor controller T stay the same, as the constant value, therefore the pressure regulating speed control, also known as constant torque speed control. (2)Adjustable magnetic speed, we usually keep the armature voltage U is rated voltage, due to the excitation circuit should not exceed the rated current, always so exciting current to reduce the trend of adjustment, the flux decline, known as the weak magnetic speed, torque T at this time also fell, then speed up. Speed control in the process, the armature voltage U the same, if I keep the armature current is constant, the output power remains unchanged, so the magnetic speed control is also known as constant power speed regulation. Figure is the armature voltage of dc motor controller in regulating and adjusting the magnetic flux control way of mechanical characteristic curve. NN is rated torque TN in the picture when the rated speed, Δ nN is rated speed. The figure shows: when adjusting the armature voltage, dc motor controller of mechanical properties for a set of parallel lines, the mechanical characteristic curve of the slope is constant, and change the desired speed motor controller, only hard to keep the original mechanical properties, so the numerical control machine tool servo feeding system adopts the regulate the armature voltage regulating method of speed adjustment. The mechanical characteristics of permanent magnet dc servo motor controller, just satisfied with the speed control requirements, therefore, nc machine tool feed system often USES the permanent magnet dc motor controller. The figure shows: adjustable magnetic speed not only changed the ideal speed motor controller, and the dc motor controller soft mechanical properties, so the magnetic speed controller is mainly used for machine tool spindle motor speed control. From the electrician learning network
