Question 2) a) A Separately Excited DC Machine was subjected to a locked rotor t

Question

Question 2) a) A Separately Excited DC Machine was subjected to a locked rotor test and a no load test. The results are below Locked Rotor Test: Vf-200V, If-15A, Va-200V, Ja-75A No Load Test: Vt-220V, la-6A Extract the parameters for equivalent circuit for this machine, and sketch the complete equivalent circuit. A DC Shunt Machine is rated for 12kW/240V/55A. Ra:0.5?, Rf250?. Rotational losses are 525W. The Ea-If relationship is: b) Speed-1200 140 Shunt field cunent.A Find: I The 11. The rotor speed when the machine is operated at rated current. Ill. The rotor speed when the developed torque is reduced 60% of the value found above. c) Calculate the inrush current in a series DC machine where Ra-0.5?, Rf 1.10, Vt-400. Sketch the Torque Speed relationship for a DC Series Machine. Ensure the axis are labelled. d) e) f Find the equation that represents the Torque-Speed Characteristic for a DC Shunt )With the aid of a sketch, explain why a resistive starter may be needed in a DC A DC machine has a no-load speed of 2000rpm and a full load speed of 1800rpm. Calculate the Speed regulation of the machine. Machine that has Ra-0.6, Rf-350, Vt 180V, lin-25A and rotor speed of 1500rpm machine, and how it works.

Explanation / Answer

Voltage regulation is given by

[N(no load) -N(full load) ]/N(full load) =[(2000-1800)/1800]*100

(1/9)*100=33%

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