Steady-State and Stability Analysis of an Analog-Type Phase-Locked Loop DC Motor Control System

A novel analog-type phase locked loop (PLL) control scheme for a separately excited dc motor is described. The steady-state analysis has been carried out to study the variation of phase angle difference between the reference and feedback signals, under no-load and load conditions. The effect of moment of inertia, amplifier gain, and differentiator time constant on stability of the system has been examined using the parameter plane method. Experimental results pertaining to a fabricated PLL controlled 5-hp dc motor are given.