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تفضلوا:

1. In recent years, solid state converters have been used to get variable dc voltage for armature control of DC motors. Consider that you have a separately excited DC motor whose field voltage is held constant. The armature voltage is to be controlled through some of these converters. You have a three-phase AC supply voltage. State at least 2 separate methods which can do the job. Explain the procedure with diagrams, and write the appropriate equations.

2. The speed of a 125hp, 600V, 1800-rpm separately excited motor is controlled by a full converter operated from a 3-phase, 480V, 60-Hz supply. The rated armature current of the motor is 165A. The parameters of the motor are Ra=0.0874, La=6.5mH, KaΦ=0.33V/rpm [note: ].

i) Find the no load speed at converter firing angle of 0 degrees. Assume that at no load armature current is 10% of the rated value
ii) Find the firing angle to obtain rated speed of 1800-rpm at rated motor current

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