Load voltage-current displacement regulator motor control system

A three-phase motor control system (FIG. 1) having a current control regulator (CCR) that includes adjustable current ramp time or adjustable current level during starting and acceleration and incorporates a load voltage-current displacement regulator (VCFB) that automatically becomes effective when the motor approaches synchronous speed, thereby to reduce the power input to the motor to what is needed to run the load, thus saving energy. Additionally, a second quadrant detector (SQD) senses overhauling load conditions and operates a gate (NG) to lock out the load voltage-current displacement feedback signal thereby allowing the reference signal to place the motor across the line until the motor operation returns to the motoring quadrant. The system further includes means (24 in FIG. 2h) affording integral control and means (30 in FIG. 2h) affording proportional control of either the current control or the load voltage-current displacement control signal, with the gain of the proportional control being individually adjustable. The integral control is provided with high gain means (FET in FIG. 2h) that is rendered effective by a switch (TR in FIG. 2h) during current control and alternative low gain means (P4 in FIG. 2h) that is substituted during load voltage-current displacement control, the gain of the latter being individually adjustable.