A DC motor, fed trough a four-quadrant chopper, works as a motor in thethird quadrant (reverse motion). The main data are Vo =120V, Ra = 0.5-ohm, La = 2.5mH, rated currentIan = 20A; rated speed nn = 3000rpm; separate excitation.
Calculatethe rated e.m.f, eg , and rated electromagnetic torque,Te.
For n =-1200 rpm and rated average current (iav =-Ian) determine the average voltage Vav,tc/T = αon and maximum and minimum motor current Imax and Imin for 1kHz switching frequency.