Performance comparison of digital AC and DC drives

The author offers the end user an understanding of the relative merits of applying AC or DC drive technology to a given application from a performance standpoint. He describes the control methods used for a digital vector-controlled AC motor drive operating without a shaft tachometer and a digital DC motor drive system, along the results of performance testing showing speed and torque responses to both reference and load changes. Experimental testing has verified that an AC vector-controlled drive, operating without a tachometer, performs comparably to a DC drive from 10% of base speed upward. By the use of slip compensation, speed regulation from no load to full load of ±0.5% to ±1% of base speed can be achieved. Below 10% speed, the system is controlled open loop slip control to standstill