A DC Shunt Motor has the following characteristics: P rated = 22.37 kW, IL = 110

Question

A DC Shunt Motor has the following characteristics: P rated = 22.37 kW, IL = 110A, VT= 240V, NF = 2700 turns per pole, n rated = 1800rpm, RF = 75Ohm, RA = 0.19 Ohm, Radj = 100 to 400Ohm If Radj is adjusted to 175 Ohm, what is the no-load rotational speed of the motor? Assuming no armature reaction and that Radj remains at 175 Ohm, what is the speed of the motor at full load? If speed regulation can be calculated as below, find the speed regulation at Radj =175Ohm. Speed Regulation% = n no-load -n full-load/ n full - load *100 If Radj is increased to 250Ohm, what is the new no-load speed of the motor? Compare this to Radj = 175Ohm. The armature reaction at full load works to reduce the total flux per pole. If the armature reaction at full load is 2000At (Ampere-turns), find the 'effective current' in the field by subtracting the armature reaction. Assume Radj= 175Ohm. What is the new speed of the motor (taking into account the armature reaction)? How does this compare to (a)? What value must Radj be changed to, to compensate for the armature reaction?

Explanation / Answer

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" https://www.dropbox.com/s/i0iahi46s8yxwau/EA324-2014-TUT-03-MEMO.pdf "

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