Analysis of Series Generator Series Motor Drive

A drive is analyzed consisting of a series-field generator, driven at a constant speed and electrically connected to a series-field motor which provides the load. The magnetization curves of both machines are assumed to consist of a linear region and two saturated regions. Both machines saturate at the same current level. Hysteresis is neglected. This system constitutes a second-order system with three nonlinear terms. The behavior of this system can be described by phase-plane representation If current and motor speed are used as the co-ordinates of the phase plane, then the phase-plane portrait will be symmetrical to the motor-speed axis. Considering all possible variations of the system parameters, two basic cases of system operation are possible. They are: 1. Steady-state current-flow exists. 2. Steady-state current-flow cannot exist. Case 1 includes ordinary system-operation as a drive. In case 2, both the generator and the motor are driven, but no steady-state power transfer between generator and motor takes place. The two basic cases will be represented by the following singular-point arrangements on the phase plane with current and motor speed as the co-ordinates: 1. One saddle point on the speed axis (current equal to zero), plus one pair of singular points symmetrical to the speed axis, which, depending on the values of the system-parameters, may be one of the following: a. Stable nodes. b. Stable focuses. c.